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Gamma-Ray Identification of Nuclear Weapon Materials

1. Gate and Delay Generator FIGURE 1 Schematic Diagram of electronic used for background measurements Software The software for the data acquisition was a commercial package from Sparrow Inc called KAMAX used version 5 2 1 of this product This software product is a fairly Gamma Ray Identification of Nuclear Weapon Materials 53 Appendix D Overview of Background Radiation Measurements flexible which always the user to design an instrument using CAMAC modules The user interface which we designed for these measurements is shown in Fig D 2 le Edit Format Windows Control Instrument Fri 12 52 PM 2 RadSig BKGl 3 elel S m C ms ECs fs NOT ACQUIRING CLEAR Hists CLEAR Ht reset True Time Update Interval Refresh Interval 8 Percent HPGe E how Cor BOLOI SI 50 Percent HPGe z 0 co M NEUTRC 8 HP 50 HF 2000 4000 000 8000 E C FIGURE 2 Graphical User Interface for the background measurements The data were collected in two ways First the data were collected so that the counts various energy was displayed in the form of histograms these data are the sum total of the data Second the data were collected in event mode where that data was time stamped every 1 4 second The data in this form gives a snapshot of the background every 1 4 second Gamma Ray Identification of Nuclear Weapon Materials 54
2. Absolute error ee Instances 1 Line tally Continuum tally Composite tally pS lS Primitive temporary tallies for line and continuum g gi g ot ey Gamma Ray Identification of Nuclear Weapon Materials 40 tcf Software Design Description Version 1 5 tcf Software Design Description Appendix A This section describes graphically how the tcf tally data are processed MCNP or COG User Header Information Multiple Tally Data User Photopeak Analysis Line Data Composite Tally Data Project Data Repository GADRAS RPF tcf Context Diagram Level 0 Data Flow Diagram Gamma Ray Identification of Nuclear Weapon Materials 41 tcf Software Design Description Version 1 5 MCNP or COG Output OUTP or Pe cogOUT Extract cog Tallies Continuum Extract like Tally Header Line like Tally Ref ine Tallies Scalars Line Tally Continuum Tally Combine Tallies Composite Tally Scaled Composite Tally RPF Repository or GADRAS Input tcf Level 1 Data Flow Diagram Gamma Ray Identification of Nuclear Weapon Materials 42 tcf Software Design Description Version 1 5 tcf Software Design Description Appendix B This appendix presents a reverse engineered description of the legacy SELECTOR pro gram in pseudocode form Portions of this description were reused in the design of tcf specifically the TallyIO and Ta
3. 1 2 Scope The tcf system is an intermediate processor between the MCNP and COG Monte Carlo particle transport programs and the data library RPF format tcf will also pro duce output in a format readable by the GADRAS and CDF2RDF programs The functions of tcf are limited t 1 Importing photon flux tallies from MCNP or COG 2 Scaling the tallies by some constant factor to account for geometric and source strength parameters in the physical problem Optionally providing output in a format equivalent to the VAX SELECTOR code Combining taking the union of the tally energy bin structures of two tallies Converting tally to proper units for use by the GADRAS code DF Oh a o Optionally writing the tallies into an RPF library archive using an agreed upon HDF RPF file structure 7 Formatting the output so that it may be read directly by GADRAS or placed into a data repository for future use in GADRAS or other tools 1 3 Definitions and Acronyms 1 3 1 Acronyms ANSI American National Standards Institute COG not an acronym GADRAS Gamma Detector Response and Analysis Software HDF Heirarchical Data Format NCSA LANL Los Alamos National Laboratory MCNP Monte Carlo Neutron and Photon transport code LANL NCSA National Center for Supercomputer Applications RPF Radiation Physics Format Gamma Ray Identification of Nuclear Weapon Materials 35 tcf Software Design Description Version 1 5 1 3 2 Definitions T
4. 0 go to lt CLOSE FILE gt Endif If kflag 2 Subtract x rays Endif Loop over i peaktot 1 scattot Write ith element of a arrays into output file End loop lt CLOSE FILE gt Close output file Prompt for more CDF files to be produced from this input If answer is yes Go to lt TOP gt Endif Close any opened input files End Gamma Ray Identification of Nuclear Weapon Materials 48 tcf man Page tcf man Page NAME tcf combine and format the tally output from Monte Carlo radiation transport codes MCNP and COG into various output formats SYNOPSIS tcf v m mult s h l rpflib f filename lt input gt output DESCRIPTION tcf accepts ascii output files produced by the MCNP or COG transport codes It extracts the particle tallies It scales these tallies according to geometric or physical constants provided by the user It refines the tallies by removing spurious flux making them represent the flux due exclusively to the continuum or to spectral lines as appropriate It will optionally produce output in the CDF format identical to the legacy SELECTOR code Otherwise it will combine the tallies into a single spectrum representing both continua and lines It will then convert to units and output format compatible with the GADRAS analysis code It will alternatively create output in the RPF dialect of NCSA HDF OPTIONS f file explicit input file designation Attempt to use th
5. Increment x index inx Set inx th elements of a arrays for energy flux amp error Endif End while If Luisa Hansen option set Close output file Reopen output file with status new 1 e overwrite Write header Loop for j 2 1 Write jth element of a arrays into output file 5 column End loop Unset Luisa Hansen option Gamma Ray Identification of Nuclear Weapon Materials 46 tcf Software Design Description Version 1 5 Set jflag 0 Seti 0 Set first flag 0 Go to lt READ LOOP gt Endif lt SET INDEX gt If kflag 1 Set kflag 2 Endif If first flag O Ifi gt 0 Set first flag 1 Endif Set peaktot 1 Else Set scattot 1 Endif Endif Endif End loop lt EOF gt If peaktot 0 Announce No groups selected Go to lt CLOSE FILE gt Endif If Dual tally flag set Subtract out the x ray flux Write the a flux quantities into output file Go to lt CLOSE FILE gt Endif If scattot O No scattering gt no cleanup needed Go to lt BYPASS gt Endif Prompt for whether to clean up file 1 e to have non photopeak data moved If answer not n Clean up file Endif lt BYPASS gt Loop over i 1 peaktot If kflag 2 Gamma Ray Identification of Nuclear Weapon Materials 47 tcf Software Design Description Version 1 5 For ith element add x ray flux to the flux Endif Write out ith element of a arrays into output file End loop If scattot
6. count data gamma ray spectral energy flux pairs data and statistical data This data can be either collected from or calculated for any number of detectors as either a single count spectrum or a time series of counts spectra In addition the data files must also accommodate varying types and amounts of infor mation describing the origin history and contents of the data It is desired that this header information be readable by the user These data files must also be flexible extensible and portable across various platforms in order to avoid the problem of converting vast quantities of legacy data when modify ing adding information to the files or changing platforms The implementation of these data files will be based upon ANSI C using as few system dependent extensions as possible in order to promote cross platform compatibility Cur rent platforms under consideration are UNIX HP Sun PC DOS and Windows and Mac Mac OS A spectral file format that we developed a number of years ago the CDF file provided a good starting point for the solution of our problem A CDF file is an ASCII file that has a variable length and content header consisting of keyword labels followed by value e g nchan 4096 delimited by the keywords beginheader and endheader fol lowed by the spectral data The spectral data could consist of up to five columns of information More than one spectrum could be sequentially st
7. D Overview of Background Radiation Measurements In this report we describe several measurements of naturally occurring gamma ray and neutron background radiation These measurements were mad in several different loca tions The locations were varied to determine the possible breadth of the variation of the radiation background In this document we describe the experimental philosophy of the background measure ments In this discussion we include information about the location where the back ground measurements were performed Next we discuss details of the experimental measurements This discussion includes details of both the hardware and software used to perform the measurements We performed a series of measurements with several detectors which included gamma ray detectors both High Purity Germanium detectors HPGe and Sodium Iodide detec tors NalI and neutron detectors The idea of the series of measurements was to estab lish an understanding of the nature of background radiation in various locations in essence to get a baseline database of the natural background radiation If a baseline background radiation is determined it is then possible to establish the possible presence of a non natural source of radiation We performed background measurements in three different locations Other locations were considered but time did not allow for all of the measurements to be performed we will discuss other possible
8. accurately Adaptive binning addresses the problem by reducing the Gamma Ray Identification of Nuclear Weapon Materials 5 A General Approach to Gamma Ray Signature Recognition impact of the continuum on the value of RSS The continuum between photopeaks is treated as a single large channel the details of the shape of this region are thrown out while the overall amplitude is preserved This technique eliminates the necessity of detailed modeling of the continuum although the high sensitivity of the amplitude of the continuum to the source geometry remains Nonetheless using this technique observed spectra and theoretical or template spectra can more quickly and effectively be compared Hundreds Hundreds rs od ne od Principal Mutti H al gt component component 2 analysis signature Pu gt Feature i extraction FIGURE 3 Application of principal component analysis to obtain a single multicomponent signature for gamma ray signature recognition The features of hundreds of computed characteristic spectra are extracted by adaptive binning prior to the principal component analysis The analysis yields a single multicomponent signature whose components in linear combination can describe spectral shapes of the original characteristic spectra Signature recognition of an unknown spectrum is then accomplished simply by a single fit to the multicomponent signature by multiple linear regression as illustrated i
9. data repository in HDF format for future use in GADRAS or other tools 1 3 Definitions and Acronyms 1 3 1 Acronyms ANSI American National Standards Institute COG not an acronym GADRAS Gamma Detector Response and Analysis Software HDF Heirarchical Data Format NCSA LANL Los Alamos National Laboratory MCNP Monte Carlo Neutron and Photon transport code LANL NCSA National Center for Supercomputer Applications RPF Radiation Physics Format4 1 3 2 Definitions Gamma Ray Identification of Nuclear Weapon Materials 30 tcf Software Requirements Specification Version 2 2 Tally Quantity representing a particle flux and statistical variance in an interval of energy or bin as output by a particle transport code Also somtimes used to refer to a list of such quantities Variance When applied to the results of Monte Carlo particle transport calculations represents the spread in values of the particle tally or more precisely the variance O is given by o N5 NY 1 4 References 1 Briesmeister J MCNP A General Monte Carlo Code for Neutron and Photon Transport Los Alamos National Laboratory LA 7396 M Rev 2 addenda 1986 1988 1991 2 Buck R et al COG Users Manual Lawrence Livermore National Laboratory UCID M 221 1 July 1994 3 Mitchell Dean J GADRAS 95 User s Manual Sandia National Laboratories Sys tems Research Center 5900 August 9 1995 4 Ham Cheryl L Radiation Physics Format Too
10. gamma ray pulse height spectra at that time Exploratory work done using experimentally generated characteristic spectra for individual radionuclides was encour aging and provides more concrete examples of what can be expected One of the experi ments was directed at studying variations in the shape of Nal spectra of 6 Co taken through six combinations of scattering and shielding materials In all 94 spectra were taken They are all plotted together in Fig 6a The first three principal components accounted for 94 of the variance in the data set and are shown in Fig 6b PC2 PC1 PC3 FIGURE 5 Signature identification is accomplished by projecting the unknown spectrum into the principal components space Its identification probability is determined from its euclidean distance in standardized units from its nearest neighbors In this notional diagram we shown an unknown spectrum rep resented by a black dot The dashed circle represents a one standard deviation uncertainty in its location This unknown is most likely plutonium since it over laps the green domain representing a variety of plutonium spectra The projection of 94 spectra into the principal components space is shown in Fig 7 Clustering of the spectra into regions representing the scattering and absorbing materi als produces domains similar to those envisioned in Fig 5 Gamma Ray Identification of Nuclear Weapon Materials 7 Project Structure 200 P
11. is high not atypi cally more than 90 of the total counts recorded Gamma Ray Identification of Nuclear Weapon Materials 2 Full spectrum analysis A General Approach to Gamma Ray Signature Recognition 2 In spite of the fact that we know in detail the gamma ray emission spectra of the individual radionuclides of interest the exact nature of the gamma ray signatures from the actual objects of interest are unknown This occurs for three reasons e We don t know the isotopic mixture of the radionuclides in the object e The objects of interest have varied and unknown geometries leading to geome try dependent signatures e Various materials will normally lie between the object and the detector further altering the already geometry dependent signature Both the object itself and intervening materials cause scattering of radiation result ing in partial energy degradation of the primary radiation In the case of intervening materials already degraded radiation from the object can be further degraded This scattering and further scattering within the detector typically assigns most detect able events to a continuum between the photopeaks in the spectrometer s pulse height spectrum 3 Signals from commonly encountered natural and man made gamma ray sources can compete with signals of interest and cause false alarms In spite of these difficulties NWM spectra still retain unique but typically subtle fea tures that c
12. is routinely used by statisticians as an automated means to find complex signatures The principal components have desirable properties that are well suited for multiple linear regression e They are orthogonal e They are automatically sorted from the most to the least significant e If the original components are carefully chosen then the principal components have physical significance e Most of the variation in the collection is explained by the first few principal compo nents These few principal components can be used as a single multicomponent signature 1 e as regressors in multiple linear regression and related characteristic spectra will cluster together in the principal component space providing for signature interpolation Princi pal component analysis is discussed in more detail in Appendix A Our approach to principal component analysis is illustrated schematically in Fig 3 The feature extraction step in the illustration is a key element in this project Generally we will not retain the spectral data in the original pulse height bins We will rebin the data adaptively to a smaller number of bins to emphasize structural features and deemphasize the continuum This is because one of the most significant drawbacks to the use of mul tiple linear regression is that the value of the goodness of fit estimator RSS is dispro portionately affected by data in the continuum a highly variable region notoriously difficult to model
13. needed detection efficiency However these highly efficient but low energy resolution detectors introduce their own problem Because they typically do not produce resolved photopeaks the spectral data are more challenging to interpret The most sensitive spectral identification from scintillators is obtained by using the most general approach to gamma ray signature recognition That is to analyze the pulse height spectrum in its entirety This exploits the entire signal in the case of weak signals in high backgrounds and recognizes the fact that most of the observable counts may lie in the continuum As traditionally practiced however the power of full spectrum analysis is severely degraded if signature alteration occurs because of scattering and absorption by interven ing materials This Lifecycle Plan focuses on a general approach to analyzing such data while remaining equally useful with higher resolution detectors Fig 2 schematically summarizes the domains of applicability of photopeak analysis and full spectrum analysis for gamma ray signature recognition as a function of signal strength detector energy resolution and signal degradation from scattering and absorp tion A General Approach to Gamma Ray Signature Recognition A general gamma ray signature recognition capability must be able to cope with the fol lowing three obstacles that are commonly encountered 1 Low signal to noise ratio The signals are sparse and background
14. A BAG AANE HERETER H EEDS iari TEE i i i f i i 4 Akl de tad arte a tiin j k nm M pa A a Aeh K AE H a E a a Ae ep a ke Arap a aala riram ap ap A Bei I RAE E T AE A I R E a H A a g ba Maen itabeveversaerr DAN Ava mits We m a a H i i H i b i i i 1 H i i i i Ei 1 m hk ee eG Re hki dd ee eee ee me ead ee A E HE a H i fi i i i i i j i i i i A R A Pe P Bee Ph i i ieii ypy H H i F E H a ed nee RE EE einen O 7 H i H i i Oe One FL Rags i PERPER T N AA MERA RELEADA SR AWA MAAA AAE A EE PA DEEA E A pean LL db y ara m a e iyi o o o TT ASIN 99S WossewUeb xni enuja ASIN 09S wWo seuweb xn enUSIdyIG eee r 13 Energy keV variance of the Monte Carlo process Notable differences on the plots at low energy reflect the high variance for transport of these weakly penetrating the COG code a are equivalent to those for MCNP b within the statistical gamma rays FIGURE 8 The results for transport of gamma rays from shielded HEU from Gamma Ray Identification of Nuclear Weapon Materials V 1095 0 1 u02 Accomplishments in FY 1996 Counts 1x10 Background Bare HEU 1x104 Shielded HEU Bgd Shielded HEU 1x10 1x10 1x10 1x10 0 500 1000 1500 2000 2500 3000 Energy keV FIGURE 9 Computer synthesized sodium iodide gamma ray pulse height spectra from HEU and backgr
15. AD processing options from execute line IF running in verbose mode THEN WHILE stream not empty READ tally from stream ASSIGN tally to be line like continuum like or neither ignore END WHILE READ multipliers from console ELSE terse mode assumed READ first tally into line like tally structure READ second tally into continuum like tally structure END IF PREPROCESS tallies REMOVE continuum tally flux from line like tally gt line tally REMOVE line tally flux from continuum like tally gt continuum tally IF selector formatted output desired THEN PRINT header information PRINT line tally PRINT continuum tally EXIT END IF CONSTRUCT composite tally data structure COMBINE line and continuum tallies into composite CONSTRUCT primitive line tally data structure CONSTRUCT primitive continuum tally data structure MERGE line and continuum tally energies into line tally primitive COPY line tally primitive energies into continuum tally primitive and composite tally REBIN the line tally into the line tally primitive REBIN the continuum tally into the continuum tally primitive ADD the line and continuum tally fluxes to find the composite tally flux SCALE tallies using multiplier s CONVERT tally to GADRAS units Gamma Ray Identification of Nuclear Weapon Materials 38 tcf Software Design Description Version 1 5 IF RPF formatted output desired THEN OPEN RPF file WRITE RPF header
16. C1 49 5 1000 100 800 i 0 G 5 600 100 O 200 5 PC2 30 3 N 400 45 E 100 Eo 0 c C 0 N 100 9 100 0 1000 2000 O a Energy KeV 3 PC3 13 9 a 94 Co spectra taken through 5 six combinations of absorbers 0 1000 2000 Energy KeV b First five principal components FIGURE 6 Plots of 94 Co spectra taken through 6 combinations of absorbers are shown in Fig 6a Feature extraction in this case relied only on rebinning the original 256 channel spectra into 32 bins with bin widths increasing in proportion to the energy resolution of the spectrometer These first three principal components of this data set are shown in Fig 6b and account for 93 7 of the variance in Fig 6a Project Structure To produce a multicomponent signature principal component analysis requires a large set of signature samples The only practical way to obtain a set of gamma ray signatures representative of the variety of NWM configurations and industrial and radiopharma ceutical sources is by computer simulation This occurs for two reasons e A pure experimental approach would require a large number of measurements of NWM which has become prohibitively expensive We have reserved our measure ments of NWM to a few items here at LLNL for validation of our computer simula tions Experimental measurements also have the disadvantage of being detector dependent e Simulated radiation signatures have the advantage that the most
17. SELECT1 gt Endif If first flag set Go to lt SELECT3 gt Endif Complete prompt for fine bins direct only If answer is yes Set jflag 1 Go to lt SELECT1 gt Endif lt SELECT3 gt Complete prompt for coarse bins scattered and direct If answer is yes Set jflag 1 Set point source flag p Go to lt SELECT1 gt Endif Go to lt SELECT1 gt Endif If point source flag p Do point source subtraction Go to lt CLOSE FILE gt Endif If igroup is even number and kflag 2 Complete prompt for x rays set kflag 0 Gamma Ray Identification of Nuclear Weapon Materials 45 tcf Software Design Description Version 1 5 If answer is yes Set kflag 1 Endif Endif Complete prompt for current CDP set jflag 0 If answer is yes Set jflag 1 Endif lt SELECT1 gt If jflag or kflag 1 If jflag 1 Increment outer loop index 1 Set first elements of a arrays for energy flux amp error Use cut value for energy 1 Endif If kflag 1 Set x index inx 1 Set first elements of x arrays for energy flux amp error Endif Begin loop to read tally lines While get line 4 TOTAL If read error Go to lt Set Index gt Endif Read a tally line Set origflx flux Scale flux by multipliers Scale abserr by multipliers If jflag 1 Increment outer loop index 1 Set 1 th elements of a arrays for energy flux amp error Endif If kflag 1
18. UCRL ID 127436 Gamma Ray Identification of Nuclear Weapon Materials T B Gosnell J M Hall C L Ham D A Knapp Z M Koenig S J Luke B A Pohl A Schach von Wittenau J K Wolford February 3 1997 This is an informal report intended primarily for internal or limited external distribution The opinions and conclusions stated are those of the author and may or may not be those of the Laboratory Work performed under the auspices of the U S Department of Energy by the Lawrence Livermore National Laboratory under Contract W 7405 ENG 48 DISCLAIMER This document was prepared as an account of work sponsored by an agency of the United States Government Neither the United States Government nor the University of California nor any of their employees makes any warranty express or implied or assumes any legal liability or responsibility for the accuracy completeness or usefulness of any information apparatus product or process disclosed or represents that its use would not infringe privately owned rights Reference herein to any specific commercial product process or service by trade name trademark manufacturer or otherwise does not necessarily constitute or imply its endorsement recommendation or favoring by the United States Government or the University of California The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of Calif
19. ad time of the experiment measured in decimal seconds count_clock_time double This contains the elapsed clock time of the experiment measured in decimal seconds It is equal to the count_dead_time plus the count_dead_time Gamma Ray Identification of Nuclear Weapon Materials 24 Appendix B Radiation Physics Format Energy Calibration Keywords These thirteen keywords describe various energy calibration parameters energy_calibration_type char This describes the type of energy calibration used Valid options are none nor mal polynomial and binned None means that no calibration is available Nor mal uses the keywords intercept slope and quadratic to calculate the energy calibration via the formula energy value quadratic bin_number bin_number slope bin_number offset Polynomial uses the number_of_energy_coeffs coefficients stored in energy_calibration_coeffs to calculate the energy calibration using a higher order polynomial equation The intercept is stored in energy_calibration_coeffs 0 The slope is stored in energy_calibration_coeffs 1 The quadratic term is stored in energy_calibration_coeffs 2 and so on The spectrum option stores the number_of_energy_bin_edges bin edges in the energy_calibration_spectrum array intercept double This is the intercept for the normal mode of energy calibration intercept_error double This is the intercept error for the normal mode of energy calibration slop
20. ally Quantity representing a particle flux and statistical variance in an interval of energy or bin as output by a particle transport code Also sometimes used to refer to a list of such quantities Variance When applied to the results of Monte Carlo particle transport calculations repre l i i E sents the spread in values of the particle tally or more precisely the variance 0 is 2 2 2 given by o N9 lt N 1 4 References 1 Briesmeister J MCNP A General Monte Carlo Code for Neutron and Photon Transport Los Alamos National Laboratory LA 7396 M Rev 2 addenda 1986 1988 1991 2 Buck R et al COG Users Manual Lawrence Livermore National Laboratory UCID M 221 1 July 1994 3 Mitchell Dean J GADRAS 95 User s Manual Sandia National Laboratories Sys tems Research Center 5900 August 9 1995 4 Ham Cheryl L RPF Spectral File Keyword Data Dictionary Lawrence Livermore National Laboratory January 12 1996 5 Ham Cheryl L Radiation Physics Format Tools Reference Manual Lawrence Liv ermore National Laboratory August 29 1996 2 0 General Description The tcf system supports the Gamma Ray Signature Recognition Project It is one of a group of programs that convert files containing scientific data into and out of Radiation Physics Format RPF a dialect of the NCSA Heirarchical Data Format HDF In addi tion to this conversion tcf scales photon flux tallies and combines them in a physically correc
21. amma Ray Identification of Nuclear Weapon Materials 22 Appendix B Radiation Physics Format location char This ASCII string contains a description of the location where the experiment was performed latitude char This ASCH string contains the latitude of the location where the experiment was performed longitude char This ASCII string contains the longitude of the location where the experiment was performed experimenters_names char This ASCII string contains the names of the people involved in conducting the experiment experiment_id char This ASCH string contains the experiment identification label run_number int32 This is the run number which resulted in the data attached to this header number_of_bins int32 This contains the first dimension of the data block associated with this header This would be equivalent to the number of channels for a gamma ray spectrum number_of_units int32 This contains the second dimension of the data block associated with this header This would be equivalent to the number of spectra in a time series of gamma ray spectrum number_of_boxes int32 This contains the third dimension of the data block associated with this header This would be equivalent to the number of experiments stored in the HDF file Hardware Identification Keywords These nine keywords identify the experimental hardware and their parameters The use of high_voltage superfine_gain fine_gain coarse_gain
22. an make them recognizable The most straightforward approach to full spectram analysis is to cycle through a collec tion of templates precomputed gamma ray signatures for nuclear materials expected to be encountered These templates are compared serially to the observed spectrum Identification is made by choosing the template that best matches the observed spec trum This approach works well even with weak signatures as long as the signature has not been significantly degraded by scattering and absorption of intervening materials An example of where such a technique can work quite well is monitoring deplaning pas sengers at a customs check point However in more demanding applications there are number of drawbacks associated with such an approach While other approaches have been investigated experience has shown that the most use ful tool for comparison of full spectra is multiple linear regression Multiple linear regression minimizes the variance weighted residual sum of squares RSS of a linear combination of pulse height spectra such as background and plutonium presumed to make up the observed spectrum 1 For completeness we mention here that in some detection scenarios particularly nuclear search background radiation intensity and spectral shape can change very rapidly and complicate the analysis In passby scenarios the radiation signature of the object of interest can also vary due to a time dependent change in so
23. and shaping_time are depen dent upon the type of instrument used instrument_type char This ASCII string describes the type of instrument used in the experiment Gamma Ray Identification of Nuclear Weapon Materials 23 Appendix B Radiation Physics Format instrument_id char This ASCII string contains the instrument serial number or other identification high_voltage double This describes the high voltage adjustment used superfine_gain double This describes the superfine gain adjustment used fine_gain double This describes the fine gain adjustment used coarse_gain double This describes the coarse gain adjustment used shaping time double This describes the shaping time used detector_type char This ASCII string describes the type of detector used in the experiment detector_id char This ASCH string contains the detector serial number or other identification Experiment Time Keywords The following five keywords contain timing and location information for the experi ment count_start_date char This ASCH string contains the date when the experiment s data collection was started stored in ANSI standard format count_start_time char This ASCII string contains the time when the experiment s data collection was started stored in ANSI standard format count_live_time double This contains the live time of the experiment measured in decimal seconds count_dead_time double This contains the de
24. cally for gamma ray spec trum analysis Although the second year s funding was denied we made substantial progress in several areas to enhance our core capabilities The most important of these are summarized below Radiation Physics Format RPF We developed the RPF to solve a perennial problem of the radiation physicist how to transfer radiation data obtained experimentally or computationally in a variety of data structures between a variety of computer codes on a variety of computing platforms RPF is a set of callable C language functions based on National Center for Supercom puting Applications NCSA Hierarchical Data Format HDF a platform indepen dent format designed to handle large complex sets of scientific data RPF can easily accommodate data in the wide variety of forms used in this LDRD and other related efforts RPF data can originate as instrumental data or computational simulations of experi ments from single detectors detector arrays and networks of disparate detectors Total count data can be stored as a time series or as multi channel scaling Spectral data can currently be stored as pulse height spectra Time stamped list mode storage for spectral data is planned for a later version Data can be mixed within a single RPF file Time series of spectra or gross count data from multiple detectors can be stored within a sin gle RPF file This would allow for example disparate measurements from a series of related
25. clear Weapon Materials 29 Appendix C tcf requirements specification design description and man page Appendix C tcf requirements specification design description and man page tcf Software Requirements Specification Version 2 2 1 0 Introduction 1 1Purpose The purpose of this document is to present in a precise and easily understood manner all system requirements deemed necessary for the tally configuration and formatting tcf system which replaces the SELECTOR GADCDF code series Upon review this document shall become a baseline defining a complete set of high level system require ments for the system developer Each requirement is described in a manner that may be tested by a prescribed method Requirements apply at the system level 1 e they may be assigned to software hardware and or operators 1 2 Scope The tcf system is an intermediate processor between the MCNP1 and COG2 Monte Carlo particle transport programs and the data library RPF format tcf will also pro duce output in a format readable by the GADRAS3 program The functions of tcf are limited to 1 Importing photon flux tallies from MCNP or COG 2 Combining taking the union of the tally energy bin structures of two tallies 3 Scaling the tallies by some constant factor to account for geometric and source strength parameters in the physical problem 4 Formatting the output so that it may be read by the GADRAS code or placed into a
26. ctor Response We made free field measurements of gamma ray standards of activ ity with a variety of high and low resolution detectors for use in producing the detector response models needed for signature calculations Ongoing response model work was curtailed at the end of FY 96 NWM Measurements We made free field measurements of several nuclear weapon pits of various designs using the same detectors These spectra were intended for validation of our spectrum synthesis capability and for algorithm testing Code Validation Our researchers use two Monte Carlo radiation transport codes MCNP from LANL and COG from LLNL The complex deep penetration radiation signature model prepared for Gamma Ray Identification of Nuclear Weapon Materials 11 Measure representative sample of background variations Production calculations of a representative sample of gamma ray signatures Overview of project status Accomplishments in FY 1996 John Nuckolls was computed using both MCNP and COG and in spite of their use of different crossection libraries they produced results that were equivalent within the sta tistical variance of the calculations Fig 8 The remaining spectrum synthesis valida tion work was curtailed at the end of FY96 We instrumented a van with both high and low resolution gamma ray detectors and took large number of gamma ray spectra along the sea shore low background at LLNL medium background and in downto
27. difficult time con suming and expensive part of the calculations Monte Carlo radiation transport are detector independent Detector dependent response functions can subsequently be folded into the computed flux to obtain the pulse height distributions for any detec tor of choice Gamma Ray Identification of Nuclear Weapon Materials 8 Project Structure kae o o m m Ii ii a 2 gt lt x lt m uj aS aS Z wo T Q Q 5 amp 30 25 20 15 10 5 0 5 10 25 20 15 10 5 Principal axis 1 Expl 49 5 Principal axis 1 Expl 49 5 Polyethylene Concrete poly Steel Steel poly Steel concrete Lead poly FIGURE 7 Two dimensional plots showing the 94 Co data projected into the space formed by the first three principal components Clustering of the spectra by the type of intervening material through which the gamma rays passed is clearly evident Using an ensemble of computer codes we have demonstrated our ability to simulate the complex signatures from thick NWM sources to accuracies of 5 or better This set of codes was satisfactory for producing a few simulations at a time Producing the signa ture set for this LDRD required an upgrade of our capability to perform production sim ulation This project proceeded along six lines of effort with the first five devoted to providing the large data set required for signature recognition algorithm development and a final
28. dy accounted for by PC 1 It can be thought of as that direction obtained by a second rotation about PC 1 that aligns along the first minor axis of the variance hyperellipsoid In general the ith principal component PC i is that linear combination which has the largest variance of all linear combinations which are uncorrelated with all of the previously determined j 1 principal components It is possible to determine as many principal components as there are original variables However in most practical problems most of the total variation in the data is usually accounted for by the first few components Furthermore the analytic goals of parsimony and independence are typi cally achieved with this method In other words a linear combination of the first few principal components can be used to describe the entire data set with considerable accu racy and their linear independence makes them ideal as regressors in multiple linear regression Algorithms for extracting the principal components are described extensively in the lit erature However in practice the analyst usually relies on one of the many excellent commercial multivariate data analysis software packages to perform principal compo nent analysis Gamma Ray Identification of Nuclear Weapon Materials 17 Requirements Conceptual Solution Appendix B Radiation Physics Format Appendix B Radiation Physics Format This file format must accommodate neutron
29. e double This is the slope for the normal mode of energy calibration slope_error double This is the slope error for the normal mode of energy calibration quad double This is the quadratic factor for the normal mode of energy calibration quad_error double This is the error in the quadratic factor for the normal mode of energy calibra tion number_of_energy_coefs int32 This is the number of energy coefficients for the polynomial calibration option energy_calibration_coef double This contains the array of actual coefficients for the polynomial calibration option The intercept is stored in energy_calibration_coef 0 The slope is stored in energy_calibration_coef 1 The quadratic term is stored in energy_calibration_coef 2 and so on Gamma Ray Identification of Nuclear Weapon Materials 25 Appendix B Radiation Physics Format energy_calibration_coef_error double This array contains the error in the corresponding coefficients for the polyno mial calibration option number_of_energy_bin_edges int32 This is the number of energy bin edges required for the energy calibration This value should equal number_of_bins 1 energy_calibration_spectrum double This contains the array of energy bin edges for the data associated with this header energy_calibration_spectrum 0 contains the leftmost bin edge The remaining number_of_energy_bin_edges 1 bin edges are the energies of the right bin edges energy_calibra
30. e file file as input This option is required whenever the v verbose option is given to disambiguate the input data stream from interactive user commands Otherwise stan dard UNIX I O redirection is preferred h help Print a brief paragraph explaining the available options and their corresponding uses rpflib create append to RPF library Output the line continuum and combined tallies in RPF format RPF is a dialect of NCSA HDF developed by C L Ham at LLNL m mult apply aggregate multiplier Scale tallies by a single quantity mult representing the product of all component multipliers present in the transport problem The user must compute this quantity before execution to use this option This option obviates the need to enter component multipliers individually during processing Gamma Ray Identification of Nuclear Weapon Materials 49 tcf man Page NOTES SELECTOR Process the tallies only as far as the legacy SELECTOR code would This includes extraction and pre processing to create true line and continuum flux tallies as well as scaling Produce output in the CDF format identical to the legacy SELECTOR code verbose Process tallies in verbose mode This option permits the user to select from an arbitrary number of tallies which may be present in the transport code output It prompts the user to decide for each tally it encounters whether the data represent a desired line tally continuum
31. e indices 1 and igroup Begin loop to read in and write out tally data loop forever Read a line If line contains TALLY or CELL and not IMPORTANCE or FLUCTUAT then Skipping down to top of tally data Increment igroup Write igroup to stdout as DATA GROUP If line contains TALLY then expecting 8 lines to follow Begin loop on j 1 9 to read and echo lines to stdout Read a line Echo lt 80 chars from line to stdout If line contains ENERGY go to lt SELECTO gt Endif End loop Endif If line contains CELL then expecting line to follow Begin loop on j 1 8 to read and echo lines to stdout Read a line Echo line to stdout If line contains ENERGY go to lt SELECTO gt Endif End loop Endif If line contains DETECTOR LOCATED then expecting lines to follow Begin loop on j 1 8 to read and echo lines to stdout Read a line Echo line to stdout If line contains ENERGY Gamma Ray Identification of Nuclear Weapon Materials 44 tcf Software Design Description Version 1 5 go to lt SELECTO gt Endif End loop Endif lt SELECTO gt Energy sentinel found Do we want this data Write partial prompt Do you want to select this group If dual tally flag y Complete prompt for x rays If answer is yes Set dual tally flag d go to lt SELECT1 gt Endif Endif If point source flag y Complete prompt for Luisa Hansen option only If answer is yes Set jflag 1 Set luisa 1 Go to lt
32. e strength and active detector area 2 2 4 Combining the tcf system combines MCNP or COG line and continuum type tallies into a single tally which 1s a function of the union of the two energy domains 2 2 5 Converting the tcf system converts units for use by the GADRAS code sys tem 2 2 6 Formatting the tcf system formats the results of the combining and scaling operations in a form compatible with one of 1 The legacy GADCDF program 2 An HDF RPF data repository or 3 The GADRAS program directly 2 3 User Characteristics The users of the tcf system will in general be domain experts with experience in judging the overall accuracy of the system s output 3 0 Specific Requirements Specific requirements are listed in this section they are 1 Functional Requirements Performance Requirements 2 3 Design Constraints 4 Attributes 5 External Interface Requirements 3 1Functional Requirements Funl00 The tcf system shall have the ability to accept photon flux tally input from the output of calculations done with the MCNP Monte Carlo transport program Funllo The tcf system shall have the ability to accept photon flux tally input from the output of calculations done with the COG Monte Carlo transport program Fun 120 The tcf system shall have the ability to produce output in the Radiation Physics For mat RPF dialect of the NCSA Heirarchical Data Format HDF Gamma Ray Identification of N
33. eader file plus an HDF data file and replace the header infor mation of that HDF data file with that found in the ASCII header file This will provide the user with the flexibility desired and in a more timely manner while minimizing demands on the implementer Gamma Ray Identification of Nuclear Weapon Materials 19 Keywords Keywords Appendix B Radiation Physics Format None of these utilities have yet been implemented Current thinking is that when fund ing is secured these utilities will be implemented in the highly portable language Java There will be a standard set of keyword labels with specific definitions This list will evolve with time and will be made available in documented form Some header informa tion updates in existing HDF data files may be required depending upon the scope and nature of the evolution This uniformity of labels and usage is essential for the success ful integration of utilities and applications Description It is imperative for the portability of data between our applications to have a standard set of keywords in the header information section s of our HDF files This file contains the data dictionary for the keywords that will be used to describe the fields in our HDF files The initial list of keywords was developed by a committee made up of the authors of this report In order for the HDF spectral file header format and its associated software to be flexible and yet maintain their exte
34. ecification Version 2 2 Port 100 The tcf system shall compile on any system which supports the ANSI Standard C Language Port 110 The tcf system shall compile link and execute on any system which supports the POSIX 1003 standard for operating system and object libraries 3 4 Attributes Attr 100 The tcf system shall be used to process classified data up to and including the Secret Restricted Data level 3 5 External Interface Requirements Extint 100 The tcf system shall allow execution from a UNIX system command line prompt ExtiInt 110 The tcf system shall allow execution from a simulated UNIX system command line prompt under the Apple Macintosh operating system ExtiInt 120 The tcf system shall permit future execution from within the Khoros 2 0 graphical programming environment 34 Gamma Ray Identification of Nuclear Weapon Materials tcf Software Design Description Version 1 5 tcf Software Design Description Version 1 5 1 0 Introduction 1 1 Purpose The purpose of this document is to provide a description of the software structure inter faces and data for the tcf tally combining and formatting system which replaces the SELECTOR GADCDE code series The short length and scope of this document is jus tified by the limited size and complexity of this system This document is not intended to satisfy the full requirements of the IEEE 1016 1987 Software Design Description Standard
35. experiments or from arrays of detectors from a network RPF is an important new contribution to our core competency and has broad applicability First code was delivered in late FY96 and provides initial RPF functionality Currently it provides for files containing one data page header plus data although implementation in a format conversion utility can create a two page RPF file Full multipage functional ity is a minor addition and will be completed in FY97 under separate funding A format conversion utility CDF2RPF was completed to provide conversion of an older file type CDF to RPF This facilitates the ease of use for much of our legacy data More details on RPF can be found in Appendix B Gamma Ray Identification of Nuclear Weapon Materials 10 Detector calibration response function determination Validate spectrum synthesis capability Accomplishments in FY 1996 Tally Conversion and Formatting tcf Our researchers use two Monte Carlo radiation transport codes MCNP from LANL and COG from LLNL These codes produce output in the form of particle flux tallies which the Monte Carlo calculation provides at the positions of simulated radiation detectors The tallies are energy resolved and their energy bins are typically structured to accumu late flux with favorable statistics for either spectral line or continuum features but can not do so efficiently for both types of features simultaneously These dissimilar tallies m
36. green green color indicates work completed that verified its ability to produce gamma ray transport results equivalent to MCNP Gamma Ray Identification of Nuclear Weapon Materials 15 Appendix A Principal Component Analysis Appendix A Principal Component Analysis The purpose of principal component analysis is to determine independent factors 1 e principal components of a multivariate data set in such a way so as to explain as much of the total variation in the data as possible with as few of these factors as possible Consider a data set of variables X X2 X The ith principal component of this data set is p PC i wX WX WX WipX j l where the w s are weights to be estimated from the data and the X s are the original vari ables such as counts in energy bins generally expressed in standardized form This linear relationship clearly describes a coordinate rotation The total variation in the data set is given by the sum of the sample variation of the k samples totalvariation Sj 85 S where S is the sample variance of X J 1 2 p The total variation is then a measure of uncertainty associated with the observations on all p variables If as is usually the case the variables are in standardized form so that S for every j the total varia tion is simply equal to p the number of variables The first principal component PC 1 is that weighted linear comb
37. h of the requested new keywords 2 The keyword czar will submit the written request to the appropriate subset of the local community of HDF file users for feedback They will have seven calendar days to provide oral and or written feedback Initially and currently the members of the keyword review committee are the individuals that developed the initial keyword list Gamma Ray Identification of Nuclear Weapon Materials 20 Appendix B Radiation Physics Format 3 The keyword czar will consider the initial request and all the feedback resolve con flicts and render a ruling upon the request plus generate the required update to the HDF spectral file accepted keyword data dictionary 4 A detailed written ruling on the request to add modify keywords will be dissemi nated to the local HDF file user community This will include information on the original request the feedback received and the ruling rendered plus any other rele vant information such as the potential keyword data dictionary entry The local user community will have seven calendar days to submit a written appeal to the keyword czar 5 They keyword czar will resolve any appeals by repeating the described process as required 6 They keyword czar will make a detailed entry into the keyword data dictionary log book and update the keyword data dictionary as required Deleting excluding keywords There will be occasions that certain keywords and the information the
38. he highest resolution detectors high purity germanium HPGe are not practical because they are bulky heavy costly delicate and because of their cryogenic cooling requirement difficult to support in the field Newly emerging instruments using ambient temperature CZT detectors have energy resolution inferior to HPGe but are still useful for photopeak identification Unhappily the current state of the art only produces diminutive CZT crystals 1 cm or less in size Such detectors require quite strong signals to capture a useful signal from measurements of endurable duration for all but the lowest energy gamma rays CZT detectors are therefore of great est use in portable instruments that can be brought in close proximity of an item to be monitored The considerably greater detection efficiency of HPGe detectors is likely to be best employed in highly sensitive applications where their high cost and cryogenic cooling requirements can be justified Monitoring of vehicles at a border crossing is an example where signals may be very weak and highly degraded due to the contents of a vehicle A similar example would be the deployment of low resolution sensors in a Wide Area Tracking System WATS In such situations the signal can be too degraded to produce detectable photopeaks in a HPGe spectrum even if deployment of such a detector is operationally practical In these conditions large area scintillation detectors have traditionally provided the
39. he ruling rendered plus any other rele vant information The local user community will have 7 calendar days to submit a written appeal to the keyword czar 5 They keyword czar will resolve any appeals by repeating the described process as required 6 They keyword czar will make a detailed entry into the keyword data dictionary log book and update the keyword change procedure as required This data dictionary contains a list of the accepted HDF spectral file keywords their defined data type and a detailed description of the information that they contain Dates will be stored as an ANSI standard formatted string mm dd yyyy Times will be stored as an ANSI standard formatted string hh mm ss XXX This list is ordered to group keywords by functionality as opposed to alphabetically File Creation Keywords The following three keywords preserve information on the initial creation of the HDF spectral data file date_file_written char This ASCII string contains the original date that this file was written stored in ANSI standard format time_file_written char This ASCII string contains the original time that this file was written stored in ANSI standard format original_filename char This ASCH string contains the original file name used when this file was writ ten Experiment Identification Keywords The following nine keywords contain basic information to identify the experiment which resulted in the HDF file G
40. in edges for the efficiency calibration spectrum efficiency_calibration_filename char This ASCH string contains the name of the file from which efficiency calibra tion information was obtained for the data associated with this header Geometry Keywords These nine keywords describe the geometry of the experiment source_detector_distance double This is the closest approach a k a fact to face distance from the source to the detector in meters It is assumed to be the closest approach a k a face to face distance unless the geometry_description field to describes otherwise source detector distance error double This is the error in the source detector distance geometry_description char This ASCII string describes relevant experimental geometry information percent_solid_angle double This is the percent solid angle subtended by the detector as it is viewing the source geometric_correction double This is the geometric correction number_of_wall_ materials int32 This is the number of wall materials described wall_material char This array of strings contains the description of the wall material wall_thickness double This is the array of wall thickness values thickness_error double This is the array of errors associated with the wall thickness value Source Description Keywords These seven keywords describe the source used in the experiment source_description char This ASCH string describes the sou
41. ination of the vari ables which accounts for the largest amount of the total variation in the data Notionally one can imagine a hyperellipsoid that describes the sample variance about the mean val ues of the X s The first principal component is the result of a S coordinate rota tion that establishes a new axis that lies along the principal axis of the ellipsoid That is PC 1 is that linear combination of the X s say 1 For principal component analysis the variables are usually recast in standardized form so that S7 for every j and the total variation is simply equal to p the number of variables Gamma Ray Identification of Nuclear Weapon Materials 16 Appendix A Principal Component Analysis where the weights w 1 1 W1 2 W 1 p have been chosen so as to maximize the quan tity varianceofPC 1 totalvariation In other words no other linear combination of the X s will have as large a variance as PC 1 When the X s are in standardized form the proportion of the total variation in the data accounted for by PC 1 is varianceofPC 1 p p Also the weights are chosen subject to the restriction Y We 1 in order T that the variance of PC 1 will not exceed the total variation The second principal component PC 2 is that weighted linear combination of the variables which is uncorrelated with PC 1 and which accounts for the maximum amount of the remaining total variation not alrea
42. information WRITE line tally WRITE continuum tally WRITE composite tally CLOSE RPF file END IF PRINT composite tally onto output stream in GADRAS format END Output Table C 2 tcf output File Name Description stdout Combined scaled and converted line an continuum tallies from MCNP cal culation in GADRAS format stdout Preprocessed line and continuum tal 2 Header line tally and ok continuum tally lies in SELECTOR format 1 Composite tally data Disk file Same as 1 except also includes com posite tally All tallies output in RPF format 3 Header line tally continuum tally and composite tally data 3 2 Data Decomposition The tcf data are contained in several data structures which are described in the tables below All structures are defined in ANSI C 3 2 1 Header Data Structure define PROB_ID_LENGTH 3 define LINE_LENGTH 80 struct headerspec char probID PROB_ID_LENGTH LINE_LENGTH double range double offset double gamma YieldMult double solidAngleMult double timeMult double faceAreaMult double compositeMult char timeStamp 80 Gamma Ray Identification of Nuclear Weapon Materials 39 tcf Software Design Description Version 1 5 3 2 2 Tally Data Structure struct tallyspec int length Tally length int arraySize Array size double energy Photon energy double flux Particle flux double relError Relative error double absError
43. ity The model is then likely to be rejected by a 7 test Full spectrum analysis as it is currently practiced The use of multiple linear regression requires accumulating a collection of radiation signatures for sources likely to be encountered in the field The most straightforward way to apply this technique is to cycle through the collection performing the regression with each candidate signature and choosing the one that best matches the observed spectrum Fig 2 illustrates such an approach schematically There are number of drawbacks associated with such an approach Dozens Dozens SEE cael _ __ __ p a Pick U one Pu Characteristic spectra FIGURE 2 An example of full spectrum analysis as currently applied The observed unknown spectrum is compared by multiple linear regression to each of dozens of prospective characteristic signatures yielding as many results as there are signatures The best result is then picked by some criterion such as minimum value of RSS v Gamma Ray Identification of Nuclear Weapon Materials 4 A General Approach to Gamma Ray Signature Recognition 1 It is inefficient Doing multiple fits is time consuming and taxes the capability of processors suitable for small portable instruments 2 It is rigid and inflexible The fits must be done to the signatures as they are There is no means of adjusting for spectral shape alteration due to scattering 3 Itis insensitive to weak sig
44. line of effort for developing and testing the signature recognition algorithm Develop supporting utility software to enable efficient production calculations Detector calibration response function determination Validate spectrum synthesis capability Measure representative sample of background variations Production calculations of a representative sample of gamma ray signatures DOP eS m pP A Develop and test signature recognition algorithms Gamma Ray Identification of Nuclear Weapon Materials 9 Develop supporting utility software to enable efficient production calculations Accomplishments in FY 1996 During FY96 items 1 4 were largely completed Our first computed radiation signature was produced at the request of former laboratory director John Nuckolls Considerable thought planning and preparation was done on item 6 Accomplishments in FY 1996 This project was originally intended to span a two year period since it was realized by the principal investigator that baseline measurements and significant improvements to available software were required to enable implementation of the proposed signature recognition technique The production calculation of 100 s of accurate gamma ray spec tral signatures required an upgrade of our computational capability in the form of utility software to transform our disparate codes into a true ensemble We also ported and tested a multiple linear regression VAX code designed specifi
45. llyOp modules PseudoCode for SELECTOR reverse engineered Assumptions 1 Input data will consist of MCNP OUTP type files 2 OUTP type files will contain particle tallies 3 Transported particles are photons Program Statement Constants and variable definitions Get required scalar info from file containing header Prompt for filename Open file containing header info Try to read everything in the header If header found echo complete header on stdout Endif Find the cut energy and save Check status of file containing tallies Prompt for filename Open file Exit if error lt TOP gt Get name of output file Prompt for filename Open file Exit if error Attempt to get problem title by lookup in the MCNPCALC database Open database file Look for tally file name If found read problem title Else prompt for new file name or press on Endif Gamma Ray Identification of Nuclear Weapon Materials 43 tcf Software Design Description Version 1 5 Write the header into the output file Write the existing header down to the last line into the output file without change Prompt for RANGE and OFFSET and write them Prompt for various tally multipliers and write them Prompt for additional user comments and write them Write the closing lines Prompt for point source option flag If point source not chosen Prompt for dual tally option flag If dual tally chosen Prompt for x ray bin size Endif Endif lt READ LOOP gt Initializ
46. location for background measurements The first series of measurements were made on the Lawrence Livermore National Labo ratory site we will call this a semi urban site The location allowed us to understand the background in a setting that had very little man made development This location also had the distinct advantage of being close to our laboratory so it served as our final shake down for the equipment The second series of measurements were made in the financial district in San Francisco we will call this an urban site This location is distinct from the semi urban site because of the presence of large buildings made of concrete The presence of the minerals in the concrete and other construction materials serves as a perturbation to the natural back ground Therefore the background measurements will be slightly different than the LLNL background data The third location was taken at Cypress Point on the Monterey Peninsula This is a very different location than the other two locations because there only slight man made development In addition the seawater will give different types of nuclear background Other possible locations for background measurements in California are Carlsbad Cav erns because of the presence of naturally occurring radioisotopes and Yosemite National Park because of the large amount of granite in the park Gamma Ray Identification of Nuclear Weapon Materials 51 Experimental Procedure Appendix D Ove
47. ls Reference Manual Lawrence Liv ermore National Laboratory August 29 1996 2 0 General Description The tcf system supports the Gamma Ray Signature Recognition Project It is one of a group of programs that convert files containing scientific data into and out of Radiation Physics Format RPF a dialect of the NCSA Heirarchical Data Format HDF In addi tion to this conversion tcf scales photon flux tallies and combines them in a physically correct manner And in addition to RPF output tcf also creates output in a format directly readable by the GADRAS system 2 1Project Perspective The tcf system is a standalone tool for the creation of composite photon tallies given the output of a Monte Carlo photon transport problem It will render output in convenient formats for other programs to use as input 2 2 Software Functions 2 2 1 Importing the tcf system accepts input in the form of the output files from an MCNP or COG execution 2 2 2 Purifying the tcf system corrects the Monte Carlo continuum tally removing the flux due to lines contained in the line tally It similarly removes the contin uum between line bins from the line tally It thereby produces pure line and continuum components Gamma Ray Identification of Nuclear Weapon Materials 31 tcf Software Requirements Specification Version 2 2 2 2 3 Scaling the tcf system allows constant scaling of tallies to account for changes in solid angle sourc
48. n Fig 4 Compare with Feature Unknown gt vector Multi ID Pu 85 component probability gt 133Ba 10 signature unknown 5 extraction FIGURE 4 Signature recognition with a multicomponent signature First the spectral features are extracted using the same adaptive binning scheme used for the principal components analysis The multicomponent sig nature is compared to the unknown using multiple linear regression The euclidean distance from the fitted spectrum is used to assign identification probabilities We can exploit the fact that the principal component space is in units of standard devia tion to assign identification probabilities The location of the fitted spectrum is projected into the principal components space and its identification probability is determined by its euclidean distance in standardized units from its nearest neighbors clustered in PC space Fig 5 Evidence supporting the concept of using principal components regression for gamma ray signature recognition The idea of using principal components regression for gamma ray signature recognition was pursued briefly a number of years ago by the Gamma Ray Identification of Nuclear Weapon Materials 6 A General Approach to Gamma Ray Signature Recognition principal investigator However efforts to exploit these ideas were limited by the cost of experimental measurements of SNM and the cost and immaturity of computational sim ulations of
49. nals Identifying a likely candidate from the signature col lection is done not only by the goodness of the match but by the strength of the sig nal such as determined by the value of bj and its associated uncertainty o The ratio Bi o defines the signal to noise ratio of the candidate signature To minimize false alarms B o is typically required to exceed a value of 3 0 5 0 to qualify as a detec tion The maximum value of B o occurs when the signature is an exact match to the observed spectrum Inaccuracies in the signature due to scattering will cause lower values of B o resulting in false negatives when this value dips below the detection threshold A new approach The single multicomponent signature The key objective of this project was to identify a small number of spectral components that taken in linear com bination can form a single multicomponent signature that describes the signatures of all NWM and legitimate sources that might be encountered Once again we rely on a col lection of radiation signatures for sources likely to be encountered in the field In this case we increase the size of the collection to include variations on signatures for partic ular sources in order to sample the effects of likely scattering geometries Our approach was to apply principal component analysis to this collection to achieve a linear transformation that produces orthogonal eigenvectors that can reproduce all of the data Such an analysis
50. nsibility with minimal backtracking and reworking the defi nitions of the header keywords and their uses must be strictly controlled It is expected that the list of header keywords will evolve with use over time Procedures to add mod ify delete and exclude header keywords are described below These procedures although draconian in appearance are necessary to maintain the integrity and utility of the RPF format Maintaining a tight rein on the keywords from the beginning will lessen the chaos that keyword changes could cause in the future Remember not all keywords will appear in each HDF header Only those keywords rel evant to each particular header will be included in the HDF file Adding modifying keywords Changes and additions may be made to the accepted keyword list according to the fol lowing 6 step procedure 1 Submit written request for data dictionary modification to the person in charge of the keyword data dictionary Initially and currently the keyword czar will be the HDF file designer Cheryl Ham For modifications of existing keywords this request should include the a list of the current keyword s to be modified a list of the corre sponding keyword s that the requester would like to be used and a justification for each of the requested changes To incorporate new keywords the request should include a list of the new keyword s to be added a complete definition of each of the new keywords and justification for eac
51. nuclear and collateral sensors All of these are fieldable instruments ranging from large fixed portal moni tors to hand held and remote monitoring equipment For operational reasons detectors with widely varying energy resolution and detection efficiency will be employed In many instances such instruments must be sensitive to weak signals always capable of recognizing the gamma ray signatures from nuclear weapons materials NWM often largely insensitive to spectral alteration by radiation transport through intervening mate rials capable of real time implementation and able to discriminate against signals from commonly encountered legitimate gamma ray sources such as radiopharmaceuticals Several decades of experience in classified programs have shown that all of these prop erties are not easily achieved and successful approaches were of limited scope such as the detection of plutonium only This project was originally planned as a two year LDRD ER Since funding for 1997 was not sustained this is a report of the first year s progress The Gamma Ray Signature Recognition Problem Gamma ray signature recognition is straightforward if signals are strong and high reso lution detectors can be used The high energy resolution of these detectors provides unambiguous identification of radionuclides Fig 1 using photopeak search algorithms A General Approach to Gamma Ray Signature Recognition However in many applications t
52. ored in one CDF file The advantages of this solution are that the header is variable length variable content and easy to read write and modify by an application and by the user with any text edi tor This also leads to the disadvantages of the introduction of non standard keywords and that the user can easily corrupt the file Another major disadvantage is the amount of storage space that the ASCII data can consume An existing widely used noncommercial basis for the data files was sought to provide the advantages of not having to develop low level routines from scratch low cost avail ability a potentially large user base from which to draw utilities and expertise and not being tied to a commercial product and the potential fickleness and longevity of any par ticular company The Hierarchical Data Format HDF package available from National Center for Supercomputing Applications NCSA provides a good basis for the general solution to our problem The HDF WWW home page is found at http hdf ncsa uiuc edu The NCSA anonymous ftp server can be accessed across the Web at ftp ftp ncsa uiuc edu Gamma Ray Identification of Nuclear Weapon Materials 18 Specifications for the Actual Solution RPF Header Viewer and Editor Appendix B Radiation Physics Format or directly over the Internet at ftp ncsa uiuc edu Our solution was to Implement an extended CDF file using the HDF paradigm to meet our requirement
53. ornia and shall not be used for advertising or product endorsement purposes This report has been reproduced directly from the best available copy Available to DOE and DOE contractors from the Office of Scientific and Technical Information P O Box 62 Oak Ridge TN 37831 Prices available from 615 576 8401 FTS 626 8401 Available to the public from the National Technical Information Service U S Department of Commerce 5285 Port Royal Rd Springfield VA 22161 February 3 1997 UCRL ID 127436 Gamma Ray Identification of Nuclear Weapon Materials Principal Investigator T B Gosnell Co Investigators J M Hall C L Ham D A Knapp Z M Koenig S J Luke B A Pohl A Schach von Wittenau J K Wolford An FY 1996 LDRD ER Project Final Report 96 ERD 062 Contents Introduction 1 The Gamma Ray Signature Recognition Problem 1 A General Approach to Gamma Ray Signature Recognition 3 Project Structure 8 Accomplishments in FY 1996 10 Appendix A Principal Components analysis 16 Appendix B Radiation Physics Format 18 Appendix C tcf System Requirements Specification Rev 0 1 30 Appendix D Overview of Background Radia tion Measurements 51 Introduction There has been an accelerating national interest in countering nuclear smuggling This has caused a corresponding expansion of interest in the use of gamma ray spectrometers for checkpoint monitoring nuclear search and within networks of
54. ound radiation The main spectral feature in the bare HEU spectrum is a photopeak from U at 185 keV When a lead shield is placed between the HEU and the detector the green spectrum this peak is greatly attenuated and the principal contribution to the spectrum is due to the isotopic impurity lt U This uranium isotope decays rapidly through a succession of daughters and enters the thorium decay series The final radioactive nuclide in this series is Tl which contributes the characteristic peak at 2615 kev its Compton continuum and escape peaks Background radiation shown in blue also has contributions from the thorium series Gamma Ray Identification of Nuclear Weapon Materials 14 Accomplishments in FY 1996 Radiation transport MCNP Data y prams Measure ere ae gt filter korit standards Nuclides Materials Geometry Backg round Detector response Verify Test Validate results data simulation Multiple Principal Feature Cherecterietic linear component vector 8 i i pectra regression analysis extraction ID probability FY97 Existing L FY96 FIGURE 10 Flowchart of the Gamma Ray Identification of Nuclear Weapon Materials LDRD ER project The white boxes indicate existing capabilities The green boxes indicate capabilities completed in FY 1996 Work planned for FY 1997 is in the peach colored boxes The COG computer code is obviously an existing resource Its
55. r This array of strings describes the collimator s used Gamma Ray Identification of Nuclear Weapon Materials 28 THDF spectral file rejected keyword data dictionary Appendix B Radiation Physics Format Shield Description Keywords These three keywords describe the shield s used in the experiment number_of_ shields int32 This is the number of shields which are described in the shield data block shield_type char This array of strings describes the types of shields used Currently acceptable shield types include none cylindrical and complex shield_description char This array of strings describes the shield s used Comment Keywords This keyword field allows for user comments comments char This is an ASCH string that can include newlines tabs etc in which the user may make additional comments There will be occasions that certain keywords and the information they represent will be excluded from the accepted list of keywords This data dictionary contains a list of the rejected HDF spectral file keywords their description of the information and why they were rejected count_end_time It was decided by consensus by the attendees at the LDRD meeting on 12 15 96 who also happened to be the initial members of the keyword review committee that this field was not necessary since the information that it would have contained can be calculated from other header fields Gamma Ray Identification of Nu
56. rce used in the experiment Gamma Ray Identification of Nuclear Weapon Materials 27 Appendix B Radiation Physics Format source_id char This is the serial number or other identifier for the source used in the experi ment source_material char This ASCH string describes the source material declared_ enrichment double This is the declared enrichment value declared_enrichment_error double This is the error associated with the declared enrichment value measured_ enrichment double This is the measured enrichment value measured_enrichment_error double This is the error associated with the measured enrichment value Absorber Description Keywords These three keywords describe the absorber s used in the experiment number_of_absorbers int32 This is the number of absorber layers which are described in the absorber data block absorber_material char This array of strings describes the absorber material absorber_thickness double This array contains the thickness of the absorber material layers Collimator Description Keywords These three keywords describe the collimator s used in the experiment number_of_ collimators int32 This is the number of collimators which are described in the collimator data block collimator_type char This array of strings describes the types of collimator used Currently accept able collimator types include none cylindrical and complex collimator_description cha
57. ron data are stored as scientific data set SDS arrays of rank 3 to allow fields for time neutron count and detector Gamma spectra are also stored as SDS arrays of rank 4 to allow fields for time energy flux and detector Calculated gamma spectra can have additional rank for relative error absolute error if desired The use of the HDF model forces a compromise by the user who wants the advantages of an ASCII header An HDF data file is binary Tests performed on an annotated HDF data file show that the ASCII strings of the annotations are visible and comprehensi ble with listing utilities such as UNIX more and with text editors such as emacs Unfor tunately although the annotations are in order they are spread throughout the HDF data file rather than being contiguous in any one place in the file If you want to hand edit the string you can However if you substitute another string with a different length the whole HDF data file becomes unreadable The solution to this problem is to create utilities for viewing extracting and replacing the header information The viewing utility will simply open the HDF data file extract the header information and display it The utility for extracting the header will write the header information to an ASCII file This file can be hand edited by the user with his her favorite text editor The utility for replacing the header information will take this or any other valid ASCII h
58. rview of Background Radiation Measurements In this section we will describe the experimental procedure used in the background mea surements All of the hardware both the electronics and detectors were installed in a 1994 Chevrolet G30 Extended Body Sportvan The van had been purchased for a differ ent project and we were able to use it for very little cost The van was equipped with gasoline fueled generator for the electronics racks and computer equipment Hardware We used five different detectors for the measurement of the background radiation These detectors were e 8 HPGe Detector for gamma rays e 50 HPGe Detector for gamma rays e 5 by 2 inch Nal Detector for gamma rays e INS Nal Detector for gamma rays e Neutron Detector The HPGe detectors and the 5 by 2 inch Nal detector were standard gamma ray detec tors The INS Nal was a non standard 2 inch by 6 inch Nal detector with a built in Am source for internal calibration this detector was removed in later runs because it was thought the Am source would contaminate the background measurement The neutron detector was a custom built detector made with four 1 inch He tubes with the use of one inch polyethylene moderator The signal out of each of the He tubes were summed together to increase the response of the neutron detector The electronics used for these measurements were standard off the shelf electronics available from Ortec Inc and Canberra Inc A schematic diagram of
59. ry or 3 The GADRAS program directly 2 3 User Characteristics The users of the tcf system will in general be domain experts with experience in judging the overall accuracy of the system s output 3 0 Design Description This section describes the decomposition of the tcf system into specific processes and data stores Each process description includes input and output as well as the operations which transform the former into the latter The data flow diagrams in Appendix A graph ically describe the relationships between the individual processes and data entities 3 1 Top Level Process Decomposition The top level of the process decomposition which identifies the external interfaces to tcf is described below as single process involving two sources of input which by default are placed onto the standard input stream and one stream of output which likewise defaults to the standard output stream This same information is represented graphi cally in Appendix A Input Table C 1 tcf input File Name Description MPNP s text output file Tally information for photon OUTx typically the last file fluxes into simulated detec in dump sequence is used tors MCNFP tally output COG tally output COG s text output file x out Gamma Ray Identification of Nuclear Weapon Materials 37 tcf Software Design Description Version 1 5 Processing CONSTRUCT line tally data structure CONSTRUCT continuum tally data structure RE
60. s The latest incarnation of our spectral data file format solution was developed on a Hewlett Packard 9000 model 735 running HP UX version 9 01 and implemented using ANSI C standard code within the HDF version 4 0r2 framework It is a binary a varia tion on the CDF file solution in which there is a variable length variable content header describing the HDF file content and one or more sets of data with a variable length variable content header describing the data The headers can be thought of as metadata since they are data about data and are imple mented as HDF vgroups The data file header consists of a variable number of vdatas that describe the data The vdata s name can be thought of as its description or variable name The vdata s class is its category And the vdata s data is its value For example one header vdata entry might have a name of location a class designation of experiment_identification and a data value of measurement lab Data will be represented by default as 32 bit integers or 64 bit floating point numbers depending upon their requirements unless specified otherwise by the user Floating point numbers will automatically be converted from the native format of the host machine to the standard HDF format of IEEE 32 or 64 bit floating point format as required This is to promote interplatform portability a feature which is hindered by storing data using the native format option Neut
61. s MCNP has been extensively validated for this purpose in the past For further validation we acquired test data from three types of nuclear weapon pits Evaluation of these data were deferred to FY 1997 As noted above our first characteristic spectrum was the HEU spectrum calculated for former laboratory director John Nuckolls Production calculations of characteristic signatures was to begin early in FY 1997 Since a fair number of results from the production calculations needed to be available as grist for algorithm development feature vector extraction principal components analysis multiple linear regression and identification probability work was also to be done in FY 1997 Gamma Ray Identification of Nuclear Weapon Materials 12 Accomplishments in FY 1996 et T i t 7 pee mewe er eT ee il eee Pe i i 1 H H i Hnara warner A A PRA e tind a t a ee ee H 2 mm ee eed eae ee n ne enn he eee ee ee n a i TEDE AEA A ee ee ee ee a a b a a r i Serene ad th eae ee vem deems eran ones nena cee ene manan arnsaanmenaa arane Cte sarreren de weer ereeenee anges ee eee tam deren ee eene r i a a Y ABHA H H suet ew H H BPLEEEANERARAEAA AEA MAAA HEA E p mm E t inl A Pe a e eade a an eaman aea mae EATE EPEN Ep h PAA A AEL HE EE FA LAE A AE tees aa T i 1 I A H i i H i Srmzeveinimiiidam m namai a a mea aaa aaee ie a in m denememe m ein n ahe eee ey awa rt re er ee fw e maae mh inka
62. t manner Besides RPF output tcf also creates output in a format directly readable by the GADRAS system 2 1 Project Perspective The tcf system is a stand alone tool for the creation of composite photon tallies given the output of a Monte Carlo photon transport problem It will render output in conve nient formats for other programs to use as input 2 2 Software Functions 2 2 1 Importing the tcf system accepts input in the form of the output files from an MCNP or COG execution 2 2 2 Purifying the tcf system corrects the Monte Carlo continuum tally removing the flux due to lines contained in the line tally It similarly removes the contin uum between line bins from the line tally It thereby produces pure line and continuum components Gamma Ray Identification of Nuclear Weapon Materials 36 tcf Software Design Description Version 1 5 2 2 3 Scaling the tcf system allows constant scaling of tallies to account for changes in solid angle source strength and active detector area 2 2 4 Combining the tcf system combines MCNP or COG line and continuum type tallies into a single tally which is a function of the union of the two energy domains 2 2 5 Converting the tcf system converts units for use by the GADRAS code sys tem 2 2 6 Formatting the tcf system formats the results of the combining and scaling operations in a form compatible with one of 1 The legacy GADCDF program 2 An HDF RPF data reposito
63. tally or neither It also prompts for each tally multiplier individually and well as the problem range and offset tcf will stop processing if it detects a format irregularity in the input tally file s Such irregularities may include legitimate transport code output tokens which were simply not anticipated during development PROBLEMS tcf does not check to verify that it is processing photon tallies Other types of tallies can be present in problems which transport neutrons or electrons in addition to or instead of photons In the unlikely event that line and bin edge energies should exactly coincide the tcf flux correction will give an incorrect result for the affected line and bin DIAGNOSTICS tcf gives contextual information about the transport problem as well as each tally label as it processes the tally It gives timing Statistics at the end of execution tcf flags if it encounters format problems in reading a tally or if it fails to find the expected number of tallies in the input stream gt 2 If the user requests RPF library output on a platform where RPF sup port is unavailable tcf will advise the user and quit before processing suggesting another option for output SEE ALSO Offline documentation for rpf gadras selector mcnp cog Gamma Ray Identification of Nuclear Weapon Materials 50 Introduction Experimental Philosophy Appendix D Overview of Background Radiation Measurements Appendix
64. the electronics is shown in Fig D 1 The linear amplifier were relatively important for proper measure ments The amplifiers for the various detectors were e 50 HPGe Canberra 2025 e 8 HPGe Ortec 672 e 5 by 2 inch Nal Ortec 572 e INS Nal Ortec 572 e Neutron Detector Ortec 572 The unipolar output of the linear amplifiers were inputted into directly into the ADCs The bipolar output was used to generate the signal which was used for the scalars In addition a pulser was used to determine the dead time in the HPGe electronic circuit The deadtime for the other detectors and the HPGe detectors was measured directly This dead time was determined to approximately 10 percent This dead time was due mostly to the ADC itself The ADCs which were used were ORTEC AD413 which is quad 8K CAMAC ADC In addition a ORTEC HM413 histogramming memory was used to reduce the overall dead time by reducing the interrupts from the computer The CAMAC crate control was Gamma Ray Identification of Nuclear Weapon Materials 52 Appendix D Overview of Background Radiation Measurements a Jorway 73A which was interfaced to a APPLE Macintosh PowerPC 8100 through the SCSI port 50 HPGe SCALAR Lj GATE GATE Pulser SCALAR 8 HPGe ADC 5 X 2 Nal SCALAR GATE GATE SCALAR INS Nal ADC ADC Neutron SCALAR GATE gt Linear Amplifier gt Timing Filter Amplifier Constant Fraction Discriminator
65. tion_filename char This ASCII string contains the name of the file from which energy calibration information was obtained for the data associated with this header Efficiency Calibration Keywords These seven keywords describe various peak efficiency calibration parameters efficiency_calibration_type char This describes the type of efficiency calibration used Valid options are none gunnink polynomial and spectrum None means that no calibration is avail able Parameter uses the number_of_efficiency_coeffs parameters stored in efficiency_calibration_params to store the efficiency calibration information The spectrum option stores the efficiency calibration information in the efficiency_calibration_spectrum array number_of_efficiency_coefs int32 This is the number of efficiency coefficients required for the efficiency calibra tion efficiency_calibration_coef double This array contains the actual coefficients for the parameterized calibration option efficiency_calibration_coef_error double This array contains the error in the corresponding coefficients for the parame terized calibration option number_of_efficiency_bin_edges int32 This is the number of energy bin edges required for the energy calibration This value should equal number_of_bins 1 Gamma Ray Identification of Nuclear Weapon Materials 26 Appendix B Radiation Physics Format efficiency_calibration_spectrum double This array contains the b
66. uclear Weapon Materials 32 tcf Software Requirements Specification Version 2 2 Fun 130 The tcf system shall have the ability to produce output in a format which 1s compati ble with the GADRAS detector modelling program Fun 140 The tcf system shall have the ability to produce output in a format which will facili tate photopeak analysis Fun 150 The tcf system shall permit the scaling of tallies to reflect a change in photon source strength Fun 160 The tcf system shall permit the scaling of tallies to reflect a change in detector solid angle Fun 170 The tcf system shall permit the scaling of tallies to reflect a change in active detector area Fun 180 The tcf system shall accept input data in the same format used by the previous sys tem 3 2 Performance Requirements Perf 100 The tcf system shall be capable of processing tallies at a rate such that the total pro cess execution time exceeds by no more than a factor of 2 5 times the time required for data input and output alone 3 3Design Constraints Alg 100 The tcf system shall include an algorithm for combining tally energy bin structures which has been derived from a reverse engineering analysis of the previous system 1 e the GADCDF program Std 100 Source code for the tcf system shall conform to the ANSI Standard for the C pro gramming language Gamma Ray Identification of Nuclear Weapon Materials 33 tcf Software Requirements Sp
67. urce detector geometry Such temporal considerations were not within the scope of this LDRD and can be considered independently Gamma Ray Identification of Nuclear Weapon Materials 3 Dealing with unknown spectral signatures Compare with A General Approach to Gamma Ray Signature Recognition 2 M n XiT X Bx j 1 RSS X B i 1 l l where y is the value in the ith energy bin of the observed spectrum and x is the value in the ith energy bin of the jth source spectral component These components include the spectra from sources expected to be encountered such as plutonium and an indepen dently measured background spectrum The coefficients bj are free parameters repre senting the intensities of the spectral source components and are determined by the minimization process If the statistical model the linear combination of component spectra is an accurate representation of the measured spectrum then the RSS will fol low a y distribution with v N M degrees of freedom and the expectation value of the reduced chi square 1 e X N will be close to unity The obvious difficulty of applying multiple linear regression to our signature recogni tion problem is that we do not know a priori the identities of the source spectral com ponents or how they might be altered by radiation transport These alterations are typically of considerable statistical significance yielding RSS v values in excess of un
68. ust be combined in a physically correct way prior to further processing steps such as convolution with a detector response function We developed tcf a code that automati cally parses both MCNP and COG output and combines the line and continuum spectra in a manner that conserves flux The tool then scales the results to account for problem geometry and source strength and converts to appropriate units Tcf produces its output in RPF and other specialty formats It was implemented to adhere to UNIX programming standards and has been tested on Hewlett Packard and Sun workstations It also runs and gives identical results on the Apple Macintosh Future development goals include integration into an abstract execution environment such as KHOROS refinement of the Macintosh interface adding a Microsoft windows interface and more comprehensive screening of the input stream for anomalies A requirements specification design description and man page for tcf can be found in Appendix C Iteratively Reweighted Least Squares IRLS Our final algorithm is intended to initially proceed by fitting of measured spectra to our multicomponent signature by multiple linear regression We ported to both Windows 95 and Macintosh platforms and tested an existing untested VAX code written by the principal investigator especially for gamma ray spectrum analysis We will seek other revenue sources for IRLS documentation publication and code distribution Dete
69. will make a detailed entry into the keyword data dictionary log book and update the keyword data dictionary as required Modifying the keyword change procedure It its allowed that the procedures for changing the header keyword list might require modification at some point in time 1 Submit written request for procedure modification to the person in charge of the key word data dictionary Initially and currently the keyword czar will be the HDF file Gamma Ray Identification of Nuclear Weapon Materials 21 HDF spectral file accepted keyword data dictionary Appendix B Radiation Physics Format designer Cheryl Ham The requester should include a description of and a justifica tion for each of the requested changes additions and or deletions 2 The keyword czar will consider the request and if deemed necessary will submit the written request to the appropriate subset of the local community of HDF file users for feedback They will have seven calendar days to provide oral and or written feed back 3 The keyword czar will consider the initial request and all the feedback resolve any and all conflicts and render a ruling upon the request plus generate the required update to the Modifying the keyword change procedure 4 A detailed written ruling on the request to add modify keywords will be dissemi nated to the local HDF file user community This will include information on the original request the feedback received and t
70. wn Oakland high variable background Details of the instrumentation and data acquisition are described in Appendix D Our first computed radiation signature simulated a specific nuclear smuggling scenario at the request of former laboratory director John Nuckolls We modeled a 1 Kg source of HEU and demonstrated the effects on the spectrum from a fairly thin lead shield For comparison to background radiation we approximated background with a mixture of potassium thorium and uranium in soil Fig 9 The structure and status of this LDRD ER at the end of FY 1996 is shown in the flow chart in Fig 10 On scenarios we decided to look at attempts to smuggle a nuclear weapon pit We performed calculations to simulate the transport of gamma rays from a 1 Kg HEU source and demonstrated that the COG and MCNP radiation transport codes produce equivalent results The data filter is the tcf utility described above Work on a Radiation Physics Format file type is also described above We measured gamma ray standards of activity for with a number of detectors of varying efficiency and energy res olution in order to compute their response functions The detector response function cal culations were not completed in FY 1996 as indicated in the figure As described above we did instrument a van and acquire background data for the same detectors The work showing equivalency of COG and MCNP results provided partial validation of our simulation capability a
71. y represent will be deleted or excluded from the accepted list of keywords The following list describes the procedure to delete or exclude a keyword from the accepted header keyword list 1 Submit written request for data dictionary modification to the person in charge of the keyword data dictionary Initially and currently the keyword czar will be the HDF file designer Cheri Ham This request should include the a list of the current key word s to be deleted or excluded and a justification for each of the requested changes 2 The keyword czar will submit the written request to the appropriate subset of the local community of HDF file users for feedback They will have seven calendar days to provide oral and or written feedback 3 The keyword czar will consider the initial request and all the feedback resolve any and all conflicts and render a ruling upon the request plus generate the required update to the HDF spectral file rejected keyword data dictionary 4 A detailed written ruling on the request to delete exclude keywords will be dissemi nated to the local HDF file user community This will include information on the original request the feedback received and the ruling rendered plus any other rele vant information The local user community will have 7 calendar days to submit a written appeal to the keyword czar 5 They keyword czar will resolve any appeals by repeating the described process as required 6 They keyword czar

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