DIS-1 Dosimeter USER'S GUIDE
Contents
1. After washing remove the DIS 1 from the solution and allow any excessive solution to drip back into the washing container If in holder Open the protective steel spring by inserting the DIS 1 in a special tool Wipe the contact area with a cotton pad Do not use excessive force while wiping 11 15 Rinse the DIS 1 thoroughly by first using water in a suitable container to dissolve any possible contamination into the water and finally under running water Any remaining decontamination solution should be wiped from the surfaces of the DIS 1 Drying the DIS 1 Dry the DIS 1 with soft tissue Place the DIS 1 in an oven at 50 C for 16 hours Use purified alcohol and a cotton pad to wipe the contact area When drying the holder of the DIS 1 use e g a cool air blower to dry the water on the surface of the holder Use soft tissue to dry the parts of the holder and place the parts in an oven SPECIFICATIONS Radiation detected Detector type Energy range Dose measurement range Calibration accuracy Energy response Directional response Maximum possible measurement time Power supply Dose read out Temperature range Operational humidity Casing Enclosure class Dimensions Weight Gamma x ray and beta Three DIS Direct lon Storage detectors and two MOSFET detectors H 10 H 0 07 15 keV 9 MeV photons 6 keV and higher beta 240 keV 2 2 MeV 10 uSv to 1 Sv 1 mrem to 100 re2. DH SL and SH These are symbolical names where the D stands for Deep Dose element Hp 10 and the first letter S stands for Shallow Skin Dose element Hp 0 07 The second letter gives the approximal dose measuring range S Sensitive Range 0 4000 uSv L Low Range 0 1000 mSv H High Range 0 1 40 Sv Channel is for connecting the element with the measuring electronics Sometimes this term is used instead of the term element It should not be mixed with a channel of the spectrometer Chamber The chamber can be assumed to be a cavity filled with gas and surrounded by walls an ion chamber This term has been used occasionally when discussing one element of the DIS 1 MOSFET This is a special type of an element where the radiation detection is based on the measurement of the Vgs parameter of the MOSFET transistor Hard Reset Hard Reset is a procedure where the physical state of the dose information of the memory element is changed with a special procedure This means that the charge which has been stored in the AME is set to the zero dose state This procedure is irreversible once it has been completed 4 15 DIS 1 User s Guide Ver 1 04 MKV MW Assignment Reset Assignment Reset is performed when the dosimeter is given to a ARA new user assigned or issued This occurs at the start of the D i control period The performed reset is a purely di
3. In practical applications this means that the signal 1 is read from a memory cell when the charge exceeds a certain threshold value In the new type of non volatile memory the amount of the charge in each memory cell has been made fully variable which in turn controls the output signal of the element Now the memory cell can be used to store analog information Figure 2 shows the structure of a standard Analog EEPROM memory cell The charge in the floating gate can be set to a predetermined level by tunnelling electrons through the oxide layer The charge is then stored permanenty in the gate due to the fact that in the normal operating temperature range the electrons have a very low probability of exceeding the energy barriers in the metal oxide and oxide silicon interfaces A high purity level is essential in the silicon dioxide formation process during the manufacture of these devices to free the oxide in any mobile charge carriers of which Na ions are usually the most dominant Today it is possible to manufacture memory cells that are capable of retaining a stored charge for hundreds of years 5 15 Reading the stored information is carried out by measuring the channel conductivity of the transistor without disturbing the stored charge In order for the ionising radiation to have an effect on the stored charge either a new charge has to be brought to the gate or an existing charge be removed lonising radiation incident on the oxi
4. DIS 1 User s Guide Ver 1 04 MKV MW INTRODUCTION The new RADOS DIS 1 personal dosimeter is based on an ionisation chamber combined with a modern electronic Direct lon Storage DIS memory cell The lon chamber is widely used as a reference detector in radiation detection and is now available in everyday dosimetry applications The DIS 1 dosimeter could be described as a passive electronic TLD or Film badge which can be read infinitely and non destructively without any loss of dose information This unique feature allows the user of the DIS 1 to instantly read his her accumulated doses whenever necessery The DIS 1 badge has a small lightweigth rugged and watertight construction which makes the DIS 1 badge reliable and easy to use The radiological range of the DIS 1 covers the entire Hp 10 and Hp 0 07 photon and beta energies without any compromises The wide dose and energy range the ability to operate in pulsed fields and the performance at high dose rates make DIS 1 an ideal device for all kinds of radiation dosimetry applications The DIS 1 allows for the detection of heavy high energy ions and its immunity to any external interference is unequalled There are no deviations in the dose Figure 1 readings even at very high EM or RF fields The excellent radiological features and the easy and fast reading of the DIS 1 dosimeter make the new DIS based RADOS dosimetry system superior to any Film dosimetry or TLD system without
5. hours after the hard reset The reset assignment function should be performed when the DIS 1 has cooled down to room temperature If the reset function assignment is performed immediately after the hard reset without any annealing a small dose of approx a few hundred uSvs may remain in the 015 1 depending upon the element Reset the DIS anneal DIS 1 at 62 5 2 5 C at least 4 hours max 48 hours preferably 16 hrs cool down to room temperature at least 1 hour perform an assignment reset to DIS Longer annealing times and cooling times may be used to assure a more stable performance The Maximum annealing time of 2 days 65 C should not be exceeded The Maximum temperature of 70 C shall never be exceeded 9 15 WEARING THE DIS 1 DOSI METER The DIS 1 badge is supplied with a clip It is recommended to wear the DIS 1 dosimeter on the chest on top of the clothing Special attention should be paid at having the beta window of the dosimeter opposite the body side see Figures 9 10 Although the DIS 1 has a rugged and watertight construction the best measurement results will be achieved with careful handling of the dosimeter 10 15 Figure 10 The body side of the holder DIS 1 User s Guide Ver 1 04 MKV MW MAINTENANCE AND CALIBRATION Calibration The DIS 1 is calibrated with a sophisticated automatic system The calibration values are not expected to change during normal use In case the radiologi
6. terms of DIS technology DIS Direct lon Storage This describes the basic method of operation the charge or the ions are stored directly in the analog memory element Some of the dosimeters are entirely or partially based on this DIS measurement method The first is the DIS 1 which has now been followed by the DIS 2 and RDD 20 products DIS 1 Dosemeter also Dosimeter Direct lon Storage Detector Gamma amp Beta amp X Ray Detector Standard measuring element DIS detector is a combination of an lon Chamber and Analog Memory Element AME that converts the charge induced by the dose in the ionizing chamber into an electronically readable voltage information DBR Dosemeter Badge Reader DIS Badge Reader A reading device that measures the dose dependent voltage and converts it to the corresponding dose of the element Element Channel The Element is the basic detection unit within the DIS based product There can be several elements inside one DIS product with different types of sensitivities or mechanical constructions meaning that the elements are able to measure different types of radiation Occasionally this element is referred to as a channel or a chamber Currently there are two main types of elements in use The DIS detection element and the MOSFET detection based element There are five elements in the DIS 1 three DIS elements and two MOSFET elements The elements are DS DL
7. 20 1237 021 1237 025 1237 028 1237 032 1237 033 DIS 1 without holder DDH 1 holder with permanent attachment one time usable DIS 1 DDH 1 DBR 1 Dosimeter Reader Firmware release Ver 1 17 xx for WinELD DDH 2 snap in holder for DIS 1 DIS 1 DDH 2 RDC software WinELD Light software system licence WinELD software Client licence Maintenance Calibrating SW for DIS 1 WinELD Pro software system licence DBR 2 Dosimeter Reader Firmware release Ver 1 17 xx for WinELD 13 15 FEEDBACK FORM We are continuously working hard at supplying you with correct and easy to read technical documents However complex systems are often difficult to document describe and understand and mistakes and inadequacies may occur occasionally during the documentation process We would like to hear your opinion on this document and to correct any possible errors If you have spotted errors or should you find any part of the document unclear please let us know Make a copy of this page describe the problem and send it to RADOS To Mirion Technologies RADOS Oy Technical Documents P O Box 506 FIN 20101 Turku Finland Fax 358 2 468 4601 This way you will help us in improving our documents and thus supplying you with better documents The best feedback will be rewarded Notes on this document Name of the document Issue date EE Description of the mistake or problem Notes on the product Name of the product Ve
8. M R O N Health Physics TECHNOLOGIES Division DIS 1 Dosimeter USER S GUI DE Document Number 2096 6058 Version 1 04 TABLE OF CONTENT INTRODUCTION eq 3 TERMI NOLOGY 4 THE CONSTRUCT 7 THE 8 HARD RESET 9 WEARING THE DIS 1 DOSI METER 10 MAINTENANCE AND 9 CalibratiON sa otis das out eet Toa eit ese ele 11 Cleaning of the electrical contacts 0 ccc eect eee etna teen neta ed 11 1 aerea 11 Drying Of DISH Ds seda Saindo sas one apne 12 5 12 2 15
9. are constructed according to a design which makes it impossible to perform the Hard Reset Figure 8 gives two types of information Firstly it illustrates how the measuring ranges of all the elements are located within the total measurement range of the DIS 1 This means that when the DIS 1 is set to measure the Hp 10 dose quality from 0 to 40 Sv the range is measured using the information from three separate DIS 1 elements Secondly the picture illustrates the sub parts of all the element measurement ranges The DBR 1 reader treats these sub parts differently during the Hard Reset procedure As illustrated in Figure 8 the measuring range of the DS DL and SL channels are divided into three sub parts the No Hard Reset range the Normal range and the Hard Reset range There is also a MOSFET range These sections are described as follows m NonHR range Graphical representation of DIS 1 measurement ranges Recommended Range HardReset range MOSFET range eu SS SL j SS 0 001 0 01 0 1 1 10 100 1000 10000 100000 Dose mSv Figure 8 DIS 1 measurement ranges for various chambers 8 15 DIS 1 User s Guide Ver 1 04 MKV MW Sections of range No Hard Reset range the reader DBR 1 does not perform any physical Hard Reset actions if the total dose is within this range The assignment dose display is set to z
10. cal calibration coefficients require to be adjusted an optional software and maintenance calibrator may be used During the calibration the calibration factors for one or more of the elements may be set Cleaning of the electrical contacts If the dosimeter is used in a dusty environment it is important to clean the connector contacts regularly before making any read outs The cleaning should be carried out immediately if there are any problems with reading j the dosimeter in the DBR 1 reader Remove the DIS 1 element from the holder for the cleaning of the connector area Fig 11 Use a soft cotton swab and ethanol to clean the connector Note To preserve the connectivity of the gold plated contacts it is not advisable to use any excessive mechanical or abrasive cleaning methods Cleaning decontamination DIS 1 has a hermetically sealed metal case made of aluminum a polyimide window for the Hp 0 07 measurements and gold plated reading contacts The holder of the DIS 1 is made of anodized aluminum and includes a stainless steel contact protection spring a locking spring and a plastic part with a nickel plated clip construction The following items are required during the decontamination procedure Figure 11 Cleaning solution with neutral pH non corrosive preferred A cotton swap paper tissue etc Check that the surface of the DIS 1 window is smooth and that is has a concave shape at normal room temperature This ind
11. de layer will produce electron ion pairs but due to the very low mobility of the charge carriers in the oxide recombination occurs with a high efficiency and most of the free charge is neutralised before it is able to pass the metal oxide interface Therefore MOS dosimeters which are based on this principle have a very low level of sensitivity to ionising radiation and are not sensitive enough for radiation protection applications Control aate Floating gate Oxide Source Channel Figure 2 Analog EEPROM memory cell Electron tunneling paths Drain In the DIS dosimeter the oxide layer surrounding the floating gate has an opening allowing the surface of the floating gate to be in direct contact with the surrounding air or any other gas Now any ionising radiation incident in the air or gas produces electron ion pairs with extremely high mobility and in case there is an electric field surrounding the floating gate these charge carriers will be transferred efficiently to the gate before any recombination occurs The structure of the DIS memory cell is illustrated in Figures 3 4 Floating gate Opening Oxide Electron tunneling path Source Drain Channel Figure 4 A DIS memory cell 900 000 94569 9 4 69 Air or Gas Figure 3 A DIS memory cell surrounded by a conductive wall The ion chamber is effectively formed between the wall and the floating gate by surrounding the entire struc
12. ero when the current dose value is set as the new reference point The element that is not Hard Reset will be treated as in the case of the Assignment Reset Normal range In typical applications the Hard Reset is not necessary within this range In some special cases it may be beneficial that the Hard Reset is performed within this sub part If the following three conditions are met 1 The expected dose accumulation is greater than 1 mSv one work operation 2 the highest deep dose resolution is required 3 The total dose of the DS element is close to 3 mSv If these conditions are met it is possible to perform a Hard Reset even if the total dose is still within the Normal range The Hard Reset range When the total dose of a channel is within this range it is advised to perform the Hard Reset The MOSEFET range This is the measuring range of the DH and SH elements These elements are constructed according to a design that makes it impossible to perform a hard reset The detection methodology is different from the other elements NOTE the operational range of each element is the total range defined by these sub parts Each measuring application is a unique method and the execution of the Hard Reset has to be determined according to the case at hand HARD RESET PROCEDURE After carrying out the hard reset in the DBR 1 reader it is required to anneal the dosimeter at a temperature of 60 65 C for a period of 4
13. gital operation where the currently measured dose information is stored into a digital memory of the dosimeter for each corresponding element The successive dose read outs are compared to these stored values and the difference is indicated The procedure does not change the physical state of the elements Session Reset Session Reset is an operation where the new offset dose is SR measured and stored in the digital memory of the DIS 1 The D i measurements are later compared to these stored offset values to give the current doses Other naming conventions are Virtual Reset Soft Reset or Offset Calculation Total Dose Measured internal Dose value of element i is 01 AD Assignment Dose DBR gives 10 Dy peep Dai 07 Daskin Dose Displayed Da Dr ARp Session Dose DBR gives 10 Ds veep Ds i hp07 Ds skin Dose Displayed 0 07 ARpj SR5 Generation Generation is a unique digital signature information that is used to specify the physical and logical parameters of the dosimeter It describes possible special features of the dosimeter to the reader and system memory size filtration of MOSFET elements and PTB approval PRINCIPLE OF DIRECT STORAGE In the original non volatile solid state memory cell information is stored in the form of an electronic charge trapped in the floating gate of a MOSFET transistor Originally the memory was used only to store digital information
14. icates that the DIS 1 is still hermetically sealed Should the surface be extensively ruffled it is possible that the DIS 1 is mechanically damaged It is not advisable to place the DIS 1 into the decontamination solvent before the mechanical properties have been checked Should there be any adhesive residues from labels or tapes on the surface of the DIS 1 or holder it is advisable to clean the surfaces with a suitable solvent Any adhesive residues on the window of the DIS 1 should be left untouched to avoid any possible damage to the filter It must be noted that any labels over the window may decrease the performance of the beta and low energy photon measurements If the dosimeter is only dry cleaned it is not necessary to remove the DIS 1 from the holder When the unit is decontamined by immersing it into a solution it is advisable to remove the unit from the holder to prevent any of the decontamination solution and water from remaining between the holder spring and the holder which might cause stability or corrosion problems in the long run Remove the DIS 1 from the holder and decontaminate the DIS 1 and the holder separately Immerse the DIS 1 into the decontamination solution for a couple of minutes The temperature of the solution should be approx 30 35 C To increase the cleaning effect the DIS 1 may be shaken while immersed in the solution Ultrasonic cleaning is not recommended as it may harm the beta window of the DIS 1
15. m partially up to 40 Sv 4000 rem 10 at 10 mSv Cs 137 30 for photons 6 keV and higher 10 50 for beta E mean 200 800 keV 20 up to 60 at 65 keV 1 uSv to 1 Sv 0 1 mrem to 100 rem partially up to 40 Sv 4000 rem 5 at 1 mSv Cs 137 30 between 15 keV 9 MeV e g Cs 137 Average 662 keV 20 up to 60 at 65 keV 6 months 5 years for 10 below 5 mSv No external power needed for measurement Through a 14 pin connector with a DBR dosimeter reader Operation 10 C 50 Annealing up to 65 C max 48 h per reset Storage 20 C 60 C Up to 90 relative humidity Resistant to static discharge RF interference and magnetic fields and EMP Withstands multiple 1 meter drops onto concrete An anonized aluminum snap on holder IP 67 waterproof 41 x 44 x 12 mm in holder 47 95 x 49 x 13 24 g in holder 43 g ATTENTION The DIS 1 Dosemeter does not contain any hazardous substances and can be recycled accordingly The number of the chambers per type may vary with the generation of DIS 1 Non resetability limited energy range With a 6 mm build up plex at distance of 15 cm in front of the dosimeter tyax as specified in the IEC 61066 standard 12 15 DIS 1 User s Guide Ver 1 04 MKV MW Range of DIS technology based products Order number 1237 002 1237 003 1237 004 1237 006 1237 017 1237 019 1237 0
16. rsion or model Do Description of the mistake or problem General Notes If you need more room please use attached pages Name Company Position Address Telephone Telefax 14 15 DIS 1 User s Guide Ver 1 04 MKV MW 15 15
17. the need for complicated processing systems The doses in the DIS 1 dosimeter DIS 1 are read using the DBR 1 DIS Badge Reader To obtain the most recent dose values of Hp 10 and Hp 0 07 the user simply plugs the dosimeter into the reader head and the values are displayed in the display of the reader in a few seconds The reader can be operated in various modes It can be set in a stand alone mode where the reader only performs the measurements and displays the doses OR it can be set as a system reader device for the WinELD dosimetry system providing the range of the dose management features The system can be connected to a PC either using the RS communication port or the local area network port LAN The instant reading capability of the dosimeter allows the user to observe the accumulated doses even on a daily basis This property makes the DIS 1 practical when eliminating unnecessary doses principle of ALARA As Low As Reasonably Achievable something that is not possible with other types of passive dosimeters such as Film TLD or OSL where the accumulated dose is revealed once per month or less frequently Combining the features of unlimited dose read outs together with the possibility of storing dose information automatically into a database every time a read out is performed means that up to date information of doses is always available and the concept of the control period has a completely new approach While other passive dosimeters req
18. ture with a conductive wall as illustrated in Figure 3 For photon radiation the initial interactions take place in the wall material and the formed secondary electrons ionise the air or gas between the wall and the gate If the wall is sufficiently thin the charged particles are allowed to transfer all or part of their energy directly into the air or gas space 6 15 DIS 1 User s Guide Ver 1 04 MKV MW THE CONSTRUCTION The DIS 1 badge consists of two parts the DIS 1 dosimeter and the DDH holder with a clip The dosimeter can be easily removed from the DDH 2 snap on holder Figures 5 6 show the front and the reverse side of the DIS 1 dosimeter There is a beta window in the round area in the upper left corner of the dosimeter In order to allow the beta particles to penetrate the filter and enter the chambers the beta window filter is made of a thin foil Normally the holder protects the electrical connector in the back of the DIS 1 dosimeter Beta window Reference Point Connector DIS 1 Ddsimeter 9900654 RADOS Technology OY Figure 5 The DIS 1 front view Figure 6 and back view PLEASENOTE THAT TOUCHING THE BETA WINDOW WITH A SHARP ITEM MAY CAUSE DAMEGE TO THE DOSI METER THIS AREA MUST NEVER BE OBSCURED THE FIVE MEASUREMENT CHAMBERS The five elements of the DIS 1 are positioned inside hermetically sealed housing measuring 41x44 x12 mm Figure 7 The DS weight of the DIS 1 dosimeter witho
19. uire to be sent to a specific laboratory for read outs once per month or once per three months once within a control period the DIS 1 can be read locally with only the data being sent forwards The dosimeter needs to be sent to a laboratory only if the required check out period has elapsed or the accumulated dose has reached a pre determined threshold value This means that the amount of the manual labor required in handling the dosimeters on a regular basis is decreased significantly With the sensitivity of the DIS 1 dosimeter and the versatility of the DBR 1 reader either in stand alone or entry exit reader mode the ELD system is ideal for all types of control and or legal dosimetry applications The DIS 1 has the added flexibility of storing and measuring recording a The total dose received to the badge since the last Hard Reset Calibration b The assignment Dose of the user since the issuing date as well as c The session dose measurement This feature allows the dose record to be kept for legal dosimetry reporting but allows the dosimeter to be reset and to receive doses for either specific time periods Day Week Month or specific tasks DIS 1 also makes it possible to optimize the TOTAL number of dosimeters required in a session where the number of controlled individuals changes due to the fact that issuing the dosimeter to a new person is easy 3 15 TERMI NOLOGY The following table summarizes some of the most frequently used
20. urrent dose reading is stored in the DIS 1 internal memory and subtracted from the total dose upon a read out In this case the stored physical dose information is not lost but can be recalled at any time with the DBR 1 reader It is recommended to use the Session Reset only when the accumulated dose is low and there is a need to reset the dose frequently daily or weekly The Assignment Reset should be used only when the dosimeter is issued to a new user The Assignment Reset does not perform the physical hard reset but enables the reader to operate as if the hard reset were performed In order to remove the dose permanently from one or more of the elements a Hard Reset is performed The Hard Reset removes the charge physically from the floating gate of the detector memory element The Hard Reset should only be used when necessary The Hard Reset is controlled by the DBR 1 after the user has activated it The DBR 1 will not perform the Hard Reset if the accumulated dose is less than the predetermined threshold dose This threshold dose element is element dependent and is approx 15 of the maximum of the range for the DS element and approx 2 of the maximum of the range for the DL SL elements If any successive hard resets are attempted only the assignment reset will be performed An annealing shall be performed after a hard reset As stated earlier there are five elements in DIS 1 The elements are DS DL DH SL and SH The DH and SH elements
21. ut the holder is approx 24 g Three of the five elements are DIS based ionization chambers and two are MOSFET detectors The DS element for the Hp 10 dose has a measuring range from 1uSv to 4000 uSv The DL and SL elements for Hp 10 and for Hp 0 07 respectively have measuring ranges from 0 01 mSv to 1000 mSv The DH and SH elements are MOSFET transistors measuring doses above 1 0 Sv to 40 Sv A regular Mo check of the dosimeter is required when dose of 10 Sv is accumulated gt X Figure 7 The five chambers of DIS 1 The Measurement ranges and resolutions of the different elements Generation 9 and older Resolution of display 1 4000 uSv 1 4000 uSv 1 uSv 4 1000 mSv 4 500 mSv 0 01 mSv 0 1 0 Sv 40 Sv 5 40 Sv 100 mSv 0 01 1000 mSv 0 01 500 mSv 0 01 mSv 1 0 40 Sv 0 5 40 Sv 100 mSv Check every 10 Sv 7 15 THE OPERATION All the chambers of the DIS 1 measure continuously It is not possible to switch off any of the elements When the received dose exceeds the maximum of the range of the DS element the readout is continued with the DL element When the dose of the DL element exceeds the maximum of the range the read out is switched to the DH element The same applies to the SL and SH elements Resetting the dose of the DIS 1 using the DBR 1 reader can be carried out in three ways In the Session Reset the c
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