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Manual for Canadian Elmitec PEEM

1. Simple non heatable holder We have this holder in two different thicknesses for thinner and thicker samples This holder can accommodate fairly large sized samples 13 mm x 13 mm square or 18 mm diameter circle The sample is hold in place using a double sided carbon conductive tape Non heatable holder with cap This holder is based on the Elmitec heatable holder base but lacks a heater or thermocouple A cap must be used to hold the sample in place This holder has a special titanium adaptor image left for transferring the sample into the preparation chamber These capped Elmitec sample holders can accommodate samples of the size 10 mm x 10 mm or 14 mm diameter circular discs or smaller Heatable holder The heatable sample holders are capable of heating to a maximum temperature of 2300 C based on a blackbody radiation from a heated filament up to 600 C or an electron bombardment heater for higher temperature See the Elmitec manual for sketches and a description of capabilities These heatable sample holders are extremely fragile and expensive and are only to be used for applications that require sample heating When working with PEEM samples and the sample holders users must follow strict UHV procedures Clean gloves must be worn when handling the sample holders tools and samples All samples and tools must be UHV clean Mounting samples on flat holders Samples can be mounted using carbon conductive tap
2. Video On button You should see a continuously updating image in the image display region If image is black then adjust the image display controls You can dynamically change the averaging and dwell while in video mode by changing the value in the appropriate text box and hitting enter Chart mode allows continuous acquisition and display of images while collecting data from these images and any other defined signal channels There are two things to keep in mind while using chart amp video mode 1 none of the data is saved and 2 it is slower maximum refresh rate is about 3 times a second Data from any existing regions of interest ROIs or other signals will be displayed in the spectra graph To use this mode click on the Chart check box and click on the Video On button you cannot dynamically change this while in video mode but must stop and restart To use video mode without charting other data insure that the Chart checkbox is unchecked 32 Spectral and Image Sequence STACK Acquisition Spectra and image sequences use a common procedure the only difference being that in image sequence stack mode the images are saved whereas in spectra only mode they are not Spectra and stack collection is governed by the Acquire Form which will be detailed in this section It is accessed by clicking on the Acquire Spectra Stack button on the main window Acquire Estimated Time to Completion 0 02 57 Kg 29000 250 0
3. Camera Setup Iv Active SensiCAM v 2 Long Exposure B W 1280x1024 CCD ee z E Elec Temp 36 Image Dimension 640x512 Cancel e ms 2000 ms 50 Image Size 640kb Binning Timing Horizontal 2 E Exposur Vertical Delay CCD Region of Interest OOOO we X High h a How to acquire a flat field image e Select Set up under camera signal on the Lox screen e Select the desired binning and CCD area of s feld Flat Field Path ake Fla interest You must use this for subsequent Fe ctsaara 2008 08 data Y Low Y High 1024x1280 pixels 25 e Click OK to exit camera set up e Turn on lox video mode with a dwell time suitable for video rate imaging These instructions assume that you can see a PEEM image on the screen e Increase the objective lens current substantially to lose all structure in your image that originates from the sample e g typically above 2100 mA In this defocused mode you should see the three dark spots from the MCP but no other structure Adjust the flux with beamline slits or the Hg lamp NOT with the MCP voltages to keep the count rate low enough to avoid non linear amplification e g bright spots say below 400 counts in 200 ms NB we sometimes turn the MCP voltages down to avoid damage from high flux this changes the amplification e You now have an image that represents the response of the MCPs Stop video mode You may wish to restart Lox
4. Removing a Sample from the Manipulator onto the Transfer Rod O To remove the sample from the manipulator follow the above process in reverse 2 3 Operating the PEEM Microscope on a Synchrotron Beamline This section assumes that microscope is running its magnetic optics are well aligned the microscope is optimized on a synchrotron beamline and a new sample has been loaded into the microscope 2 2 above This text is written to accompany formal training on the PEEM microscope A separate users guide to Lox follows in Chapter 3 Separate start up procedures starting from a cold microscope and details optical alignment procedures are outlined separately below 2 3 1 Sample Alignment Preliminaries This section assumes that you have just loaded a sample on the PEEM manipulator that the sample voltage power and image intensifier power supplies are turned off and that the valve to the beamline and the column valve are closed Step 0 Verify the following e Ensure that the contrast aperture is fully retracted position lt 7 mm e Ensure that the field of limiting aperture position is at 10 mm e Ensure that the energy filter exit slits are removed top of energy filter position 10 mm e That the vacuum in the main chamber should be in the low 10 torr range e That the lens power supply rack and camera PCO are on e Ensure that the programs LEEM 2000 and Lox are both running Start LEEM2000 first
5. Updated 29Sep07 Pressure should be lt 5E 9 Torr before opening any valve 16 3 Change to PEEM branch select branch pull down menu 4 Select the grating and EPU harmonic appropriate for your experiment 5 If you are just starting to run after a fill it may be useful to select your desired photon energy the undulator will take some time to run in A OO 7 Double check that the PEEM column valve and the manual valve is shut this is to protect the multichannelplates in the PEEM from sudden over exposure 8 Open the photon shutter PEEM branch control program and any other valves in the beamline that may be closed SM Beamline Control System Soft X ray Spectromicroscopy 10ID 1 RingStatus 59 327mA_ Coherent Radiation studies SH1 Val PSH2 SSH IT Branch amp GratingSelection 4 EPu Monochromator Valves amp Vacuum SelectBranch BRANCH2 sTxm EPU Seti Gap 36 9084 220 3760 EF 3176 11 EE 1 153e 10 000 E 1 367e 09 Ea 2 082e 10 000 Ei 9 000e100 oo ml 4 940e 10 E 5 005e 10 i 4 097e 10 1 674e 10 Ea 1 009e 09 ope Sec 2 SelectGrating e wo EA OpenBeamline amp Branch SSH GL0SED PSH GLOSED BSH CLOSED OPEN CLOSE Qi 0 0000 Sec 4 Q2 26 280 26 2295 Sec 6 a3 9 0000 0 0010 6 SOR 3 Energy Selection Sec 8 EPU MONO Minor Grating Q4 26 2280 26 2280 O PEER ox ow ox ox Taper pooo 2 695 ae Sec 10
6. centering necessary Figure 6 1 Motion of aligned and eee misaligned fiducial markers Reference Elmitec PEEM III manual Notes e Due to the rotation of the electron trajectories by the magnetic lenses the x y orientation of the alignment lenses P2AX P2AY in this case will not necessarily correspond to the x y directions on the displayed image The motion direction for a given deflector will appear to change with the image magnification You can establish the x y axis s by moving the sample manipulator stronger lens q lens breathes Step 9 Adjust Sample Tilt Adjust the sample tilt to make the OBJ optical axis coincide with the TL optical axis NB the sample should be near the centre of its motion when aligning the tilt otherwise electric field effects from the edge of the cap will distort the electron trajectories Primary method Hg lamp sample with relatively uniform contrast e Place mouse pointer at the centre of your fiducial or click the mouse to put a cross at the fiducial 45 If your sample is relatively flat and does not have high contrast between adjacent regions the following method can be used o First reduce the Hg lamp intensity or turn down the channelplate voltages to ensure that the damaging signal levels do not occur o Reduce OBJ current until there is a bright spot on the screen OBJ 1100 1000 mA Optimize the OBJ current to make the
7. Ensure that LEEM2000 and Lox are both running and that the PEEM is ready to take photons 2 If ona beamline with more than one branch check with other users to ensure that they are not using the beamline On the SM beamline you need to coordinate with STXM users as further action will disturb their beam 3 Ask beamline SM Chithra or Drew PEEM Uday to set up the wrapper software The wrapper is a program that communicates between the PEEM software Lox and all of the CLS systems EPICS controls and signals Execution of the wrapper program or changes to the wrapper configuration are to be handled by the beamline or PEEM scientists If you can t tell if the wrapper is running go to the next step you can test with Lox 4 Start communications on the Lox side a Select set up and beamline from the pull down menus b Check the box labeled Activate Communications then Save and Close 14 BeamlineSetup M Cif M4PEEMCurrent c If communications are working a green light will illuminate on the main Lox screen e g upper right hand corner of the figure below f 29483 mef co f o E 386 Go E 1001 Go 0 00 0 00 aa 0 00 a 0 00 0 6000 Go If communications do not connect this light will not illuminate and the error 10 03 13 TCP connection error No connection could be made because the target machine actively refused it Disabling TCP communications will appear in t
8. QUIEN When moving the sample towards the objective lens take care of the distance between the sample and the objective lens Once the correct sample position is found adjust the stop ring to define this position You will need to reset the stop ring when changing between samples of different thickness Note that the manipulator can move by vacuum force when it is not against the stop ring it is best to have the stop ring set and locked at a point where the sample cannot be moved in so far as to hit the objective Additional Notes o The optimal sample objective distance for a perfect flat sample is 2 mm corresponding to 1675 mA 20 kV o Ifthe sample has sharp points or is subject to charging or field emission this field may be too large Reduce the field at the sample by moving the sample farther away from the objective lens keep the accelerating voltage at 20 keV but reduce the OBJ lens current to keep the sample in focus A somewhat higher TL current may also be necessary Step 6 Check Selected Area Aperture focus Insert the selected area aperture by the column valve to check that the edge of this aperture is in focus This step verifies that the FL currents are properly set If the FL is not properly set then it is possible to push the sample into the objective lens while tuning the field of view calibration will be incorrect The selected area aperture is positioned at the image plane between the objective lens and t
9. When you zoom in you may need to adjust the sample focus with the field lens 21 e Select the desired field of view FoV from the preset list e Refocus image with field lens less than 150 mA e When going to high magnification adjust the contrast apertures position after focusing e Uo Reduce the MCP voltage when you are going from 10 um to 100 um FOV in one step 2 5 A Brief Guide to Modes of Operation Lox Users should read the Lox instructions chapter 3 A short summary of possible Lox experiments is provided below Lox set to continuously acquire images at set dwell binning and masking parameters Thus you can adjust these parameters to obtain the desired combination of e pixel density highest 1x1 binning 1280x1024 lowest 8x8 binning e total image size controlled by the ability of the PCO camera to reduce the number of pixels transferred in pres set block sizes e image quality longer acquisition times and averaging give better statistics So far no noticeable degradation of spatial resolution has been observed at long acquisition times The best strategy is to adjust the illumination beamline slits to as high as possible consistent with desired spectral properties then increase the dwell until the upper levels in the histogram of pixels is above 50 One then selects the number of images to average in order to achieve desired quality If you leave the intensity per image very small less
10. at this point buffer clearing errors abound e In Lox increase the image dwell to get adequate statistics at the signal level e g signal half way through the histogram window e Return to camera set up Now click take flat image This will record an image of this MCP response function with the dwell selected above This file will be saved in your data directory with the extension flat e Select load flat image to load this image NB directory will default to code directory not data directory but you should know where your data is Select OK e Now you can select flat field at the front panel A warning will come up Remember that you need a recent flat field image same CCD area same binning for this to work If the binning or area is different no data will be saved e Remember to reset your objective lens current before proceeding 080604044 lox 080604048 lox 080604049 l0x i 20 40 6o 80 20 40 eo 80 x um E 0 000 e dwell 2000 00 x um E 0 000 e dwell 2000 00 s 20 40 eo 80 xum E 0 000 eV dwell 2000 00 s Uncorrected image dark correction dark and flat correction 26 2 6 3 Recording other signals 27 3 Software 3 1 A Users Guide to Lox Author Jacob Stewart Ornstein Last Modified May 20 2007 3 1 1 Preamble Lox is a Program written in Visual Basic 7 a Microsoft net product for operating an Elmitec photoemission electron microscope PEEM cu
11. be defeated Proper grounding of the PEEM microscopy chamber must be maintained Do not disconnect the ground wires yellow green wire for the PEEM frame or table Radiation Users are to follow CLS radiation safety regulations The Hg arc lamp produces UV light and has the potential to produce ozone Avoid skin exposure and do not look directly into the beam Do not open the lamp housing until the electricity has been disconnected and the lamp has cooled down If user needs to align the lamp optics use the UV goggles in the drawer on the PEEM control rack to protect your eyes from direct or reflected UV exposure 1 2 Instrument Protection If operated incorrectly the PEEM microscope can be damaged and or rendered inoperative Certain restrictions have been imposed on the instrument operation to ensure its effective long term operation The following section lists the known ways in which damage can be inflicted on the PEEM microscope Users are discouraged from adding to this list Vacuum Conditions The synchrotron and beamline vacuum is sacrosanct The beamline has vacuum interlocks but never rely on an interlock Close the valve between the beamline and the PEEM microscope when performing any unusual operation in the microscope sample loading and unloading transfer heating etc Contaminants from your sample can damage the beamline optics and the PEEM microscope A common problem is the deposition of organic species on mirror
12. circle diameter as small as possible This is the circle of least confusion or the focus of the objective lens By reducing the OBJ lens current the focal length of this lens is extended into the image plane Reduce the light intensity as required o Adjust the manipulator sample TILT until the bright spot is centered at the fiducial position o After adjustment tighten the tilt adjust screws and return the OBJ current the sample focus value 1650 1700 mA Failing to tighten the tilt screws will give instability in the recorded image Alternative method non uniform illumination or a non ideal sample e g high contrast sample topography etc You can not use the zone of least confusion to align samples that have very high contrast between adjacent sample areas or for samples with a lot of topography These effects will appear to distort the focus spot shape and you may misalign the sample For example the etched alignment test sample has sufficient topography to make this alignment problematic To align the sample tilt in these instances toggle the objective lens current and center the breathing motion on your fiducial by using four tilt screws on the manipulator It may be difficult to do this if the PEEM optics are greatly out of alignment One can align the optics and once aligned come back to fix the tilt with this method Confirm that the TL axis is the optic axis Repeat Steps 8 and 9 until the TL wobble remains
13. in and out of focus as the sample voltage is changed Method 2 Uniformly Illuminated Mostly Homogeneous Sample This method is not effective when the sample is not uniformly illuminated or the image is highly heterogeneous This method is usually used when the sample is illuminated with the Hg arc lamp The goal of this process is to adjust the sample tilt to make the OBJ optical axis coincide with the TL optical axis e Place mouse pointer at the centre of your fiducial or click the mouse to put a cross at the fiducial e If your sample is relatively flat and does not have high contrast between adjacent regions the following method can be used o First reduce the Hg lamp intensity or turn down the channelplate voltages to ensure that the damaging signal levels do not occur o Reduce OBJ current until there is a bright spot on the screen OBJ 1100 1000 mA Optimize the OBJ current to make the circle diameter as small as possible This is the circle of least confusion or the focus of the objective lens By reducing the OBJ lens current the focal length of this lens is extended into the image plane Reduce the light intensity as required o Adjust the manipulator sample TILT until the bright spot is centered at the fiducial position o After adjustment tighten the tilt adjust screws and return the OBJ current the sample focus value 1650 1700 mA Failing to tighten the tilt screws will give instability in the recorded i
14. of the signal o See the signal setup description for more details on signal types If you wish to save the images during a scan check the save images check box If this box is unchecked only the spectral data will be recorded The Dark Field Correction box should be used if you wish to remove constant dark field data from the image NOT CURRENTLY WORKING PROPERLY o If this is selected then a stack is started by taking a dark image It does this by throwing off the microscope currently by setting the Start Voltage to 400eV but this can be changed by clicking on the Dark Settings button and selecting a PEEM module and a value to set it to and taking an image which should consist entirely of Dark Noise ie the constant component of each image o This Dark Image is then subtracted from all subsequent images actually the subtraction is not quite true all negative values obtained are set to zero This dark image is also saved in the file directory so it can be added back in latter if this is necessary it is saved as a TIFF called the sample name Dark Click start scan This will close the window and begin the scan Data from the stack will be saved in a directory on the lox file path to find or change this directory look at the configuration file 36 o In addition to the main image saving routines Lox also collects and displays spectral and other types of data The data is then stored in a tab delimited format in the outp
15. to optimize e g all the shutters are open etc Contents 1 Safety and Instrument Protection sisceinsisats cenccetnnnintatenasadeussatnnetinanedadaueldietneacntatsaas 4 Vel Personal Salety esersrasion aea aA Aaa 4 1 2 Instrument Protection pricerctenctcncsotdnnnouniiasctannononsnnnibaiiacedannseaoiandeiidaoednpananaanbbiads 4 2 Basic Instrument Operations cccssseeeeeeeeeeeeeeeeeeseeeeeeeeeeeeeeeeeeseeeeeeeeeeeeeeeeeees 8 2 1 Mounting SUN SS tance cetesis destin ren aclecenesestenneduteeeneneianmussetontiemenaneaeenteckaveieneneds 8 2 2 Checklist for Loading Samples into PEEM MicroScope cccceeeeeeeeeetees 10 2 3 Operating the PEEM Microscope on a Synchrotron Beamline e00 12 2 4 CHANGING Magnification enciccnccnssncscteccscncecctannusnine ade yenedesaversdeceuantdensvessdedauaueaanies 21 2 5 A Brief Guide to Modes of Operation LOX cccceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeaeees 22 2 5 1 Recording Single Images eeeeeeseeceeceeeeeeeeeeeeaeeeeeeeeeeeeeseeneeeeeeeeeees 22 2 5 2 Recording Spectral Image Sequences cccceeeeeeeeeeeeeeeeeeeeeeeeeeeeees 23 2 5 3 Recording Spectra icien iaee lade ien ea E E ei EEE ea AE 23 2 5 4 XPS Image Sequences cccceeccceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeenaeeeeeeeeeeeeeenes 23 2 95 5 FOCUS SCAMS edhe tected teaetonodnne otuinasbettantetptuatenedeadtunoioectoletwedtas 24 2 5 6 OMS Modes a sriicccncesdienrsiatvsniinantinen
16. voltage Keep the difference between the MCP and the screen less than 4 5 kV Step 7 Operations If the microscope optics are well aligned and the sample tilt is correctly set you are now ready to operate If you are using the Hg lamp close the iris completely before turning on The lamp takes a few minutes to stabilize At this point if the column valve is open the contrast aperture is fully out the light is hitting sample and there is photoemission i e the sample work function is below the Hg lamp energy then you should see some signal on the image display NOTE The Hg lamp has a short lifetime 100 hrs when it is vertically mounted life time is even shorter when it is inclined at an angle 45 in the present case shut off when not being used for more than 10 minutes There is a bulb hour display on the front panel Order a spare when there is more than 40 hours of operation logged Troubleshoots What happens when HV readout on 20 kV PS flakes out Solution Microsoft solution Turn down the HV to zero minimum Put off the HV p s put off the lens p s put off the power supply rack enable button on the control rack Then turn back on in the reverse way This rarely happens but probability is more when there is a HV discharge in the mains chamber between sample and objective lens 53
17. you wish to add There are four types of signals in addition to ROIs Analog signals four Counter signals two PV signals two and PEEM signals two Once the signal has been selected hit the add button and you will see it appear in the signals box It can be removed by selecting highlighting it in the list box and clicking on the remove button similarly a signal s properties can be accessed by selecting it in the list box and clicking on the properties button Signal Types e Analog signals read a analog signal from a given channel from the NI card e Counter signals read a pulse signal from one of the two counters on the NI card e PEEM signals read a voltage value from the LEEM2000 control program e PV signals read a PV from the Beamline via the Wrapper 37 Signal properties To change the properties of any of these additional signals select it in the list box and click on the properties button This can be done either in the main window or in the acquire window A window like the one below will pop up allowing you to change the settings of the given signal Generally the settings are self explanatory but the PV signal setup is a little more complex The name itself is arbitrary and can be any descriptive name The object or PV radio button select whether you will use a predefined communications object for this control or use a simple string instead It is recommended that you use an established Beamline object for the PV
18. 0 200 Te oO 2 Bg 52000 505 00 3 00 Lowest To Highest ROI O Save Acquisition Load Acquisition aOmesh Go To First Energy Start Acquisition Camera Setup Dark Setu Close i F P i There are Seven types of image sequences which can be acquired Energy scans Time scans XPS scans Focus scans PEEM scans PV scans and 4 Dimensional scans Select the scan type by clicking on the appropriate tab e Energy Scans acquire images while scanning over a preset series of photon energies this is probably the most typical scan type e Time Scans acquire and display images at a specified frequency and extract ROI and other signals and display them in the Spectra Display as a function of time Generally useful only if also running a scan external to Lox on the sample e XPS scans acquire images at a series of start voltages on the PEEM This scan allows the selection of electrons of only a narrow band of kinetic energies e Focus scans acquire a set of images over several values of one of the PEEM focusing variables Field Lens or Objective Lens It is intended for use during focusing by allowing careful evaluation of the image at several different values and selecting the best one 33 e The PEEM scan is a general scan that can be used to scan any of the PEEM modules XPS and focus scans are subsets of this e PV Scan allows for the scanning of a predefined Process Variable PV such as a mirror or motor position e 4D sc
19. But if you wish and the wrapper object has also been defined you can simply enter the object name as a string in the PV textbox iol x i aci ignal a Analog Signal Set 0 xi Analog Channel Settings PV S g na Setu p Channel Mode i Differential X Name Input Type oc x Voltage Limits 10 10 C Object E nergy z Lower Upper 40 10 D py aOmesh Averaging fi Scale Value 1 38 Camera Setup This is accessed by clicking on the setup button in the Camera Signals box or by selecting Camera from the Setup menu pull down menus at the top of the Main Display This opens up the dialog screen displayed bellow which allows the user to select Camera settings The most commonly used control here will be the CCD region of interest This controls what region of the full CCD is used by Lox when acquiring an image The red box represents the region that will be used To change it click on the gray image and drag until the red box covers the region you are interested in The binning setting controls how the image is recorded with what degree of resolution Binning the image at settings above one shrinks the image file by combining adjacent pixel counts into larger pixels A setting of two for example will cut the image size by a factor of four by reading pixels in groups of four two by two region Vertical and horizontal binning should always be the same or the image will be warped Generally 2 is a reasona
20. CaPeRS Users Manual ver 3 8 November 12 2008 Users Manual for CaPeRS CAnadian Photoemission Electron Research Spectromicroscope Conventions used in this manual e RED TEXT warning e Green Text PEEM design suggestions Yellow highlighter incomplete text in manual File CaPeRS user manual v3 8 doc Version 3 8 Authors Stephen Urquhart Stephen urquhart usask ca Adam Hitchcock aph mcmaster ca Uday Lanke uday lanke usask ca Brian Haines brian haines usask ca Jacob Stewart Ornstein Last changed 12 November 2008 SGU STUFF TO ADD e New changes to the microscope o Field of view limiting aperture e M3PEEM adjustment At the start of any shift or after any beamline changes grating change between PEEM and STXM branches or suspected beam position changes the M3PEEM mirror pitch must be adjusted One can easily gain 2 orders of magnitude after adjustments e To adjust the signal get Lox running in a chart mode o Get signal on PEEM screen either in Lox field of view via an ROI or a mesh signal that is downstream of the exit slit o Set Lox scanning in time mode e g Acquire Spectra Stack Select the Time Scan tab Set up to scan many points 50 000 with a suitable dwell 200 ms and energy Press start o Once running select display to display the signal you wish to optimize o Optimize M3PEEM pitch to maximize the signal in this chart mode e g make sure that you actually have a signal
21. amera It will take several minutes for the cooler to cool reducing the noise level Step 5 Start LOX NOTE The camera program must be started after the LEEM2000 program in order to establish proper communication from LOX to LEEM2000 Set exposure time to 200 msec Use weighted average mode Set auto B C contrast level The screen should now show shot noise and hot spots from the MCP with a very low level of signal At longer dwells you will also see three small spots which are burn marks in the MCP from overly concentrated electron beams Note you must have the camera running before turning up the MCP voltages Any problems with the MCP operation will then be immediately apparent before the on set of permanent damage Step 6 Turn on Image Intensifier Power Supplies The multichannel plates MCP can be easily damaged The following steps must be followed before turning up the voltages e Verify the column chamber pressure is sufficiently low 10 torr or lower e Ensure that the column gate valve is closed SPECIAL CAUTIONS AFTER A BAKEOUT CHAMBER VENT OR CHAMBER MOVE The Screen channelplate sample and analyzer high voltages must be turned up very slowly after any chamber bakeout chamber move or venting of the column The MCP voltages must be turned up slowly taking at least one hour i e 100 V every 5 minutes 52 WAU LN MU UN Mek m CI NAY NOt fate INL CMO NCEA ARE Keep the screen voltage greater than the MCP
22. and side panels of HV rack key to lock back door to cabinet key is stored in CaPeRS tool box enable key on the front panel stored in the control rack drawer Software Errors and Debugging This is a preliminary list to be fleshed out as errors occur and are noted LEEM 2002 software NO ADAPTOR POWER There is a USB to serial adaptor in the bottom of the HV cabinet It is powered by a simple adaptor When moving the cabinet this adaptor sometimes becomes unplugged To fix open the HV cabinet and look for the serial adaptor at the bottom of the rack attached by nylon ties 41 6 Advanced Procedures 6 1 Advanced PEEM Alignment Procedures The multichannel plates MCP can be damaged if strong focused electron beams hit the detector even if the MCP voltage is off To avoid this e Shut off the photon illumination if you are about to make any change in conditions where the MCP illumination will be too high or uncontrolled This step alone will not prevent damage field emission from the sample can also damage the MCPs The best solution to protect the MCPs is to close the column valve Ensure that the pressure in the microscope column is in the low 9 s or lower Reduce the sample illumination and or MCP voltage whenever you go from a small field of view to a larger field of view Keep the MCP active between 1300 1400 V and video mode enabled That way you can see the displayed image and reduce the illumination if the
23. and wait until it is fully active before starting Lox e Make sure that start voltage is set to zero and that the LEEM2000 field of view is set to 100 micron largest field of view Step 1 Advance the sample so that it is 3 4 mm from the objective lens Step 2 Turn up the High Voltage 20 kV supply Activate the high voltage power supply and slowly turn up the voltage to 20 000 V Watch for a pressure rise as the voltage is applied due to discharges and field emission The discharge along the ceramics can raise the pressure into the mid 9 s Step 3 Start video mode imaging in LOX The Lox users guide is provided in Section 3 Start Lox in video mode with a dwell time of 200 ms in weighted average mode x S gt Display s 2 Ring Current 169 28mA 060519006 060519006 Intensity cts 1 285 290 275 280 Energy eV Acquire Single Image Rome Spectra Stack Pause z M SGM Control Camera Signal Status NonDispersive um 0 0 Shutter ENERGY EETA 287 751 ts C ah sD cee eee p Energy Offset a Chart z y Averaging Horizontal Defl mrad 0 Setup Entrance Slit um 0 25 Exit Slits ec Number of Signals to Aquire 2 Dispersive um 100 00 Auto B C constant or on click Lie 3 16 37 The acquisition was aborted Cannot start continuous image 4 ID Gap rm i z x 3 16 51 Video acquisition stopped EPU Polarizati
24. anning allows for the scan of two variables simultaneously 520 00 565 00 Lowest To Highest 00 312 00 325 00 00 920 00 940 00 1 00 E E 845 00 850 00 a m 940 00 945 00 The Energy Scan tab shown above is where a series of photon energies to scan can be defined Each row of text boxes represents one energy region to scan For each region one can define the start energy the end energy the energy step the dwell and the averaging The parameters for an existing energy region are modified by clicking on the text boxes and changing the values To create a new region click on the add region button To delete an existing region click on one of the text boxes in that region to select it and then click on the Remove Region button 34 The Time Scan tab shown above can be used to define photon energy dwell delay this is the length of time between images image signal averaging and number of images to be taken during a time scan Other Scan Types e There are other similar scan settings for XPS scans the start voltage PEEM scanning is a generic scan of any module on the PEEM PV scanning allows any defined process variable to be scanned such as IDGap exit slits or mirrors All these scans can be defined similarly to the Energry scan in their respective tabs e The only scan which has a significantly different layout is the 4D scanning The layout is shown bellow broadly the 4D scanning lay
25. ariables display can be set in the PEEM setup window The values displayed here are refreshed at the some rate as the Beamline variables usually every 2 5s 31 3 1 3 A Guide to Lox Image Acquisition Image Acquisition concepts e Dwell This is the length of time the Camera collects data for when taking an image the less intensity you have the longer the dwell you will need to collect reasonable data e Averaging This is the number of images taken and averaged during a single image acquisition if contrast is poor then more averaging is often necessary Recording a single image To acquire a single image at the current Energy and dwell time click the acquire single image button The image will be measured and saved to disk and a message will appear in the log window informing you of this fact along with the file and path names The image itself will appear in the image display If this is the first image acquired after turning on the instrument or changing settings it may be a black or white rectangle indicating under or over scale To see the image change the display settings using the image controls To auto set the contrast and brightness click the square green button in the image control region otherwise adjust manually Using Video or Chart Mode Video mode will acquire images continuously at the currently defined acquisition dwell time and display them on the screen as they are captured To turn on video mode click the
26. armonic __ Mode Ange H MONOCHROMATOR 1 Fj CirLett a p anoo O 0 000 aros 4001381 e Sec 11 Co 2 1500 2S0 Epu 0 2000 0 200 Grating 5416 19 4616 16 5 01 p offse E PEREA A 5 UsefulTools Sec 13 E 163 10 o nergy eV Sami Sec 14 EHEH caei 00 Pressure should be lt 5E 9 before opening any valve Updated 23Aug07 Contacts Chithra 341 0400 cell 3749 office Kon 3546 office Martin 3690 office 9 Carefully open the manual valve between the PEEM and the M4PEEM tank 1 ensure that the vacuum in the PEEM main chamber is below 5 x 10 torr 17 Instructions for PGM Beamline e pending Step 6b Alternate Method Image with the Hg Arc Lamp If the sample is appropriate radiation resistant you can tune up and aligned the microscope with the Hg arc lamp Turn on the Hg arc lamp and wait about 2 3 minutes for it to warm up Step 7 Open Column Valve At this point in time the beamline should be open and the photons should be illuminate the sample Lox should be running in video mode so that any signal can be detected Open the volume valve carefully and watch the count rate on the screen If the count rate is too high over 800 cps immediately close the valve You can reduce the count rate by lowering the voltage on the multichannelplates from 1450 V or by closing the exit slits To open the column valve rotate the micrometer drive
27. ble compromise of image size and resolution The timing has two components the exposure time is otherwise known as dwell time and can and should be set from the front panel the delay is the period to read the image and should not be changed Camera Setup x SensiCAM v 2 Long Exposure B W 1280x1024 CCD comnts gt i Elec Temp 29 Image Dimension 592x496 Image Size 573kb Binning Horizontal 2 Vertical 2 CCD Region of Interest X Low fi Timing Exposure ms 500 Delay ms 50 992 x 1184 pixels 39 4 Other Functions 4 1 Metal evaporation in PEEM chamber Built in lead evaporator use to make decorated Si test sample 1 Connect the Elmitec sublimation pump filament cable FIL to the evaporator BNC 2 Degas filament at 2 0 A for a while to outgas filament keep pressure below mid 9 s 3 Pb will start to evaporate at 2 7 A 4 Evaporate Pb while watching PEEM contrast will grow while imaging 5 For aclean surface you may need to remove water by heating the sample to 150 C or so However good Pb Si samples can be made when the sample is dirty 4 2 Sample Heating and Cooling Heating typical working current is 2 5 A Maximum recommended is 2 7 A The maximum current supplied is 3 A which is workable but will have a limited lifetime Refer users to the Elmitec manual for details on what can be done but give a short recipe on how to do low temperature heating Summar
28. ble that the misalignment of the Acceleration lens will be corrected by the misalignment of P2 However this is undesirable By identifying the center of the P2 lens before aligning the Acceleration lens this effect can be avoided Set P2 align x y currents to zero Toggle P2 lens current Mark on screen the P2 center Stop toggling Step 14 Center beam through Accel Lens e This step positions the beam through the analyzer such that beam is centered in Accel lens and close to center of P2 e re identify a fiducial marker e Toggle the Accel lens e The two Accelerator alignment lenses should be used together to align the fiducial with the centre of the Accel lens i Use Accel Lens Align A to get the fiducial half way to the centre of P2 this alignment lens will only move in one direction perpendicular to SEL That s OK ii Use Accel Lens Align B to get the fiducial the rest of the way to the centre of P2 It moves in the same was as Accel Lens Align A e Now use SEL to minimize motion of the fiducial e Stop Accel lens toggling e Now use P2 align to get the fiducial to the centre of the Accel lens breathing i Toggle P2 ii Move P2AX to bring the fiducial in centre of breathing Small compensation of P2AY are allowable 47 Step 15 Align P3 lens e Adjust align currents for P3 to make the trajectory of the optical axis coincide with the axis of that lens by wobbling the lens and adjust P3AX and P3AY currents until the fidu
29. centred on the fiducial after step 9 Step 10 Align imaging column Adjust align currents for each successive lens in the imaging column FL IL P1 to make the trajectory of the optical axis coincide with the axis of that lens by adjusting each lens in turn by o Wobbling the lens o Adjust LENS AX and LENS AY currents until the fiducial point is at the centre of the wobble motion o When the alignment currents are correct one of two behaviours will be observed A regular breathing centred about the fiducial OR A rotation centered about the fiducial o If the centre of wobble or the fiducial move out of the field of view adjust P1AX and P1AY to re position Repeat until the wobble for all lenses is centred on the fiducial Adjust FL to focus the image 46 e Double check the alignment of the imaging column steps 6 10 Refine as necessary Step 11 Align retarding lens RL to optical axis e Toggle the retarding lens Ret Lens e Center breathing with RetAX RetAY note that this is an electrostatic lens it will feel different from the rest of the lenses and there will be no rotation breathing Vs rotation Step 12 Align Acceleration Lens e Toggle Accl Lens use SEL to make it stable In one direction the centering will be reached by SEL e Inthe other direction perpendicular to the first it will be reached by Accl Lens Alg A e Stop toggling Step 13 Identify center of P2 lens e tis possi
30. cial point is at the centre of the wobble motion e Repeat until the wobble for all lenses is centred on the fiducial Step 16 Set Image Centre Plane of Energy Analyzer e Toggle SEL Minimize motion with Accel Lens e Stop toggling e Adjust FL to get image back in focus This puts focal image in center of analyzer Step 17 Insert the contrast aperture Insert contrast aperture and adjust for optimum position e Move aperture in until it starts to clip then use only ONE of the 45 positioner to optimize lateral position The lateral position should be such that the electron signal tracks cleanly along the motion axis of the aperture rod without clipping e Move aperture farther in until there is no signal Adjust the Lox image scaling to see the no signal background e Insert the aperture another 2 7 turns There is a vee notch followed by a 100 70 and 50 micron aperture each separated by 2 6 turns on the micrometer motion e When you find some signal adjust the micrometer drive and a 45 positioner to maximize image intensity The spherical aberration is reduced and thus the spatial resolution is highest with the smallest aperture cuts off axis rays but there is an intensity penalty Images made with the Hg lamp have very low chromatic aberration so the 70 um aperture is small enough to compensate spherical aberration and thus gives nearly the full spatial resolution e When optimizing a contrast aperture at high magnification smal
31. cision accuracy of some Beamline depends on the scan direction Sort type Unsorted will scan in the order that the regions appear Identify the signals to be acquired during the scan there are two types of signals to setup Regions Of Interest ROI and all other signals o ROls are different in that you cannot define them in the signal controls but must create them in the main window A ROI will integrate the intensities in a region of the image and display these intensities in the spectra graph and write them to a file o To define a ROI first click on the Define ROI button in the main screen You can then left click on the Main image display region and you will see a line appear you can draw a polygon with this tool by left clicking to add points Right click when you are finished and the ROI will appear in the Signals box it will look like ROI 0 in the box bellow o To add a different type of signal analog counts etc click on the drop down box select one from the currently defined signal types and then click the add signal button o If you do not wish to record one of the currently defined signals click on its name in the Signals Display and click on Remove Clear All removes all currently defined signals To change the name of a signal except an ROI to something sensible for example Analog 0 to Sample Voltage select a non ROI signal and click on the properties button then change the name
32. cking on the appropriate icon in the upper right corner The zoom is controlled by clicking and dragging the resulting rectangle over the region you want to display Click on the zoom icon again to restore the un zoomed image This display button in the upper right region of this control allows will open a window in which you may select which signals you wish to be displayed this can be changed either before or during imaging Also in this dialog you can select whether to display the primary or secondary variable in a 4D scan Log Window This is where the program displays messages to the user about what actions it has taken and any error messages Errors are displayed in bold Image controls These allow the user to set the contrast and brightness scale of the image that is displayed Alternatively the program can automatically set the brightness and contrast This can be done in two ways To auto set the contrast and brightness for the current image click on the green button To have the contrast and brightness automatically adjusted every time a new image is displayed click on the circular button which will light up to show this mode is active Histogram This displays the range of intensities available in the image It is typically used to help manual setting the contrast and brightness controls for the image and also to ensure the electron intensities falling on the image intensifier are in a safe range that value depends on the image acquisit
33. clockwise from the closed position until there is a click indicating the valve is unseated then further until the drive is fully clockwise and a scratching sound is heard This valve can leak if not seated properly Ensure that the signal on the MCPs is not in a dangerous range A new column valve selected area aperture was installed in October 2008 Following are the two positions for the column valve 3 5mm Close 17 5 mm Open The selective area aperture is mounted on the other side of the column valve The various positions for this aperture are 0 mm Open 20 mm 1 aperture 1250 micron diameter 23 mm 2 aperture 400 micron diameter 25 mm 3 aperture 1200 micron diameter If your sample is retracted 3 4 mm from the objective lens there should not be much photoemission Normally the PEEM should be aligned so that the photon illumination is highest when the sample is 2 mm from the objective lens Step 8 Advance Sample into beam Slowly advance the sample into the beam while watching the signal on the Lox screen video mode to ensure that the signal level does not damage the MCPs 18 You should eyeball the distance between the sample and the objective lens by looking in the viewports yes realize that this isn t easy particularly on the SM beamline With experience and some information about the sample thickness it is possible to guess this from the number of threads visible on the manipulator Once you star
34. crate PROTECT THE TRANSFER ARM AND VALVE Don t close the valve on the transfer arm fatal for transfer arm valve and for PEEM operations Protect the instrument vacuum Sure the main chamber ion pump is very fast but why hoses the vacuum if you really don t need to When loading samples on the SM beamline TAKE CARE to not disturb the STXM branch vibrations of this branch can create noise in their images Take care to not disturb the REIXS clean room Checklist m m D Close valve between the chamber and the beamline Close the column valve The closed position is approximately 3 5 mm on the valve manipulator You should hear a scratching noise when the valve closes USE THIS NOISE and NOT the valve position as a positive indication that the valve is closed Shut of the MCP and screen voltages turn to zero Shut off the sample HV and the HV rack Pump out the load lock o Make sure that the up to air valve is shut and turn on the backing and the turbo pumps o Pump down the lock pump chamber until the pressure on the BA gauge reads in the high 10 torr range When the pump is at full speed with a good vacuum the pump power should read 22 W Press the button labelled pump current temperature power to read this Before you open the valve between the load lock and the main chamber first o Retract the sample manipulator centre the sample tilt and x y position If you do not centre th
35. duenintndintatnandineneueedinnaitinentntitnguetatnmetneatnnnde 24 267 TIN NSS ennienni ea e a a a 25 2 6 1 Image Correcto diresis ea aaa Ee aai 25 ee E E E rhe rear ore 27 2 6 3 Recording other signals ax te iccsccercsecscncetextmantonsbiants anpeeetecedbandeqnnoutnenboaeteadees 27 3 SoftWare ssia neiaa aaa apaa aa aaa ANAKE Eaa aaia EDENN EEA ENEKE 28 3 1 A Users Guide to LOX ssssssneneeseseseeenrrnrrsertrtttnnttrsertrttttnnrtrneerttnnnnn enneren ennen 28 3 1 1 Preamble ieie nidad a dad i eia aiia 28 3 1 2 Getting Started With LOX cece cece eeeeeeeeeeeeeeeeeeeeeeeneeaeeeeeeeeeeeeeeees 29 3 1 3 A Guide to Lox Image Acquisition ceeeeceeeneeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee 32 Me Other FUNC OOS ei eeaeee eaae ee ibn ae eaa aeea ae EEEa aa aE R EAEan aSa aa 40 4 1 Metal evaporation in PEEM Chambet ceeceeeeeeeeeeeeeneneeeeeeeeeeeeeeeeeanees 40 4 2 Sample Heating and Cooling cccccccccceeeeeseseeeeceeeeeeeeeeseeeeeeeeeeeeeeeeeeeeneeaees 40 4 3 Transfer into Preparation Chamber ccccccseccceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeneaeees 40 5 Frequently asked Questions eeeceeeeeeeeeeeeeeeeeeeeeeeeeeeseeeeeeeeeeeeeeeeeeeeennees 41 5 1 Why can t turn on the High Voltage cccceeeeeeeeeseeeeeeeeeeeeeeeeeeeeeneeeees 41 5 2 Software Errors and Debugging ceeeeeeeeeeeeceeeeeeeeeeeeeeeeeeeeeeeeeeeeseeeneaeees 41 6 Advanced PrOoCOdUres wvisis
36. e CAUTION If the column chamber has been vented and baked since last operation of the image intensifier increase the image intensifier voltages slowly 100 V every five minutes 42 While watching the Lox camera screen in video mode 200 ms dwell turn on the image intensifier to operating voltage CAUTIONS ensure correct polarity Phosphor screen voltage always greater than MCP voltage voltage difference between MCP and screen voltages should not exceed 4 5 kV Operating voltages o Phosphor screen operating voltage 5600 V o MCP operating voltage 1450 V Step 3 Set Microscope Starting Parameters Ensure that all slits and apertures are in the OUT position before starting alignment Remove contrast aperture fully retracted position lt 7 mm Remove energy filter exit slits top of energy filter position 10 mm Remove both sets of field of field limiting apertures by column valve and by analyzer entrance Open column valve position 17 5 mm Set initial LEEM2000 tuning settings Set Start Voltage to zero This step is critical for proper tuning If the column alignment is performed for a different value of start then you will artificially tune the hemisphere bending to compensate Set LEEM2000 field of view to 100 micron largest field of view Set the following settings in LEEM2002 o SEL to 80 5 V o Transfer lens TL to 922 mA o Field Lens FL to 2528 mA o Intermediate lens IL to 1068 mA o Project
37. e 166 Wind noy o wee ID Gap mm o Euy ba Histogram 3 16 51 Video acquisition stopp Log EPU Polarization 0 0 Go Control 3 16 54 06051 9005 img written ID Following J On 1D Harmonic Ta ner 3 18 24 Video acquisition started images will not be saved 3000 4000 oooO O ABORT _ p Camera Signal Status 29 Pause Fal 0 ROI 1 vao rae F Chart Averaging 3 22 58 Video acquisition stopped setting Energy Main Image This is where images from the camera are displayed It also has printing and zooming capability To zoom in click on the magnifying glass icon in the upper right The View will shift the image will now be centered and will fill the screen To zoom in further click on the image and the location you wish to see in more detail Every left click zooms in by a factor of two and every right click zooms out by a factor of two To print the image click on the print button it has a printer icon and select the printer from the resulting dialog Spectra Display A graph which displays spectra that has been collected from the PEEM In addition other signals selected for recording such as data measured using the analog or counting capabilities of the National Instruments acquisition board are displayed on this same graph The default x scale is full range and the default vertical scale is minimum to maximum of all signals You can print and zoom this display by cli
38. e It is important to ensure that the samples are well connected to the holder and that they are flat parallel to the holder surface Avoid having any exposed conductive tape as this undergo photo degradation in the UV beam and seriously degrade the microscope vacuum Mounting samples on capped holders A sample which needs to be heated in mains or preparation chamber is mounted on a heatable sample holder using a Mo cap There are two different sized caps available 4 mm and 7 mm diameter hole at the center One chooses depending on the sample size After gentle tightening all the four M2 screws symmetrically the Mo cap will hold the sample in place It is advisable not to over tighten these screws as it may lead to break the sample Ensure that there is no tilt generated while mounting the sample The manipulator can adjust 2 It could be difficult to get high resolution images if sample tilt is more than 2 At this stage it is good to take the sample out from the mains and correct the tilt Helpful hint a micrometer can be used to verify that the sample cap is not tilted 2 2 Checklist for Loading Samples into PEEM Microscope General guidelines for changing samples PROTECT THE BEAMLINE ensure that the valve to the beamline is CLOSED PROTECT THE CHANNELPLATES ensure that the valve to the microscope column is CLOSED Shut off the MCP and screen HV PROTECT YOURSELF shut off the sample high voltage both 20 kV and the
39. e tilts and position you risk losing the sample puck into the ion pump Be warned o Make sure that the locking ring on the transfer arm is loose o Ensure that the Setpoint override has NOT been turned on and that the setpoint beeper has not been turned off If you have a pressure excursion the warning beeper will provide an essential indication of the pressure rise DOUBLE CHECK the list above especially the beamline and column valves and HV WHEN READY open the hand valve between the load lock chamber and the PEEM main chamber WATCH THE MAIN CHAMBER VACUUM IF it rises too fast into the 7 s be ready to close the valve and think carefully about your sample and how long you pumped the load lock 10 SLOWLY move the sample into the chamber Do not hit the manipulator s mu metal shield Remove insert the sample onto the manipulator see detail on next page Retract the sample transfer arm slowly When the transfer arm is cleared from the valve VERIFY VISUALLY close the valve Verify that the valve is closed Shut off the BA ion gauge for the load lock and then the turbo and membrane pumps Wait 2 minutes before venting the load lock to dry Nz to remove your sample Loading the sample on the end of the transfer arm Q Q n Use the long needle nose pliers UHV cleaned to hold the flat side of the sample holder It is easier to mount unmount the sample puck if you have a very good grip on the sample
40. ectron signal more than surrounding channels There are at least three permanent bright areas on the MCP screen Dark spots are present from damage to the phosphor screen there are three distinct dark spots present Non permanent damage is observed when the MCPs are exposed to high count rates often appearing as stripes or webs in the image These features can be removed with a hard bakeout however this is not convenient nor is this a practical solution therefore this non permanent damage must also be avoided The thresholds for permanent and non permanent damage are not well characterized In some circumstances a high count rate will only exist for a few pixels and be hard to see It is very important to watch histograms carefully ESSENTIAL RULE If an action might cause the MCP s to be exposed to an excessive electron count CLOSE THE COLUMN VALVE It is not sufficient to turn down the MCP voltages damage can still occur even if you are artificially counting less electrons by turning down the amplification Conditions that lead to MCP over exposure and damage e Field emission Sharp features protruding on the sample surface lead to field emission and very high electron count rates e Changing conditions In x ray imaging the x ray flux and the photoemission can change with x ray wavelength depending on the sample and beamline If you tune in low flux conditions you risk overexposure if you change photon energy open
41. energy filter slit remove so that a fiducial is in the same place when the biggest slit is in place Toggle SEL and adjust Accel lens voltage change focal length of acell lens to minimize motion of the centre of the lens Then check by putting in FOV aperture that the image plane is at the right spot FL to focus on aperture then obj to correct 50 6 2 PEEM Start up Procedures advanced This section assumes that the microscope is installed and aligned on a beamline or intended to run with the Hg arc lamp p that the vacuum is adequate main pressure lt 1x 10 Torr column pressure lt 1 x 10 Torr and that the sample has been loaded in the microscope Before starting verify e That the vacuum is adequate mid 8 s for main chamber low 9 s for imaging column e That the sample is at least 3 4 mm from the objective lens Step 1 Turn on Lens Power Supplies The PEEM lens power supplies are normally to be left on except for when the microscope is to be moved or vented This is particularly important for the magnetic lenses to avoid hysteresis The lens power supplies can only be turned on if the high voltage rack is powered If the pressure set point on the main and column gauges is tripped then power to the HV and lens rack will be off Check this interlock if you can not turn on the lens power supply Step 2 Turn on High Voltage 20 kV supply The HV power supply is interlocked to the main and column pressure ga
42. ers one scan the secondary scan on top of the first The primary scan type is selected with the combo box next to the Primary scan label The scan types are Energy Time XPS PEEM PV and Temperature untested The Settle Time is the wait time after setting a primary point and is most likely to be used with temperature scans for which the temperature will need time to rise The secondary Scan is defined similarly you can select from Energy XPS PEEM Temperature or PV for scan types The Dwells and Averaging can either be assigned by the primary scan the secondary scan or a multiple of the two In this last case you should be careful to set the dwells averaging in the secondary scan to reasonable values 1 5 as these values will be multiplied with the primary scan dwells and averaging to give final values as Z a FL ow so oe a To Define a Scan e Define the desired start values end values step size dwell and averaging settings for all of the regions you wish to scan e Use the checkboxes on the left side of the window to select which regions to scan 35 Look at the scan summary data on the right hand side of the screen to check that the scan is set up correctly number of points scan time and highest and lowest energies are reasonable If running an energy scan select the scan direction Lowest to Highest scans from low to high energy while Highest to lowest scans from high to low energy the pre
43. h the Hg lamp have very low chromatic aberration so the 70 um aperture is small enough to compensate spherical aberration and thus gives nearly the full spatial resolution e When optimizing a contrast aperture at high magnification small fields of view it is better to make fine adjustments using both 45 positioners rather than the micrometer and one positioner e IF LOST A technique for finding the center of the vee Partially insert the contrast aperture vee until it partially obscures the image Decrease the transfer lens current until the contrast aperture V comes into focus on the screen Now it is easy to find the center of the vee as well as to see the burrs from machining on the edge of the vee Once centered it is easy to do the 2 6 turns and find the center of the aperture Step 11 Insert Energy Aperture e Insert first analyzer exit slit approximately 15 mm 5 turns in from open position e Adjust P1 value to get most uniform illumination brightness Open 10 mm 1 slit 25 micron 2 slit 125 micron You should now be ready to acquire data Iterating on these steps may improve alignment High quality high spatial resolution imaging may require additional alignment of the magnetic lenses Note that the energy exit slit must be in for PEEM imaging with x ray illumination otherwise severe chromatic aberrations will distort your image This exit slit must also be in for XPS imaging 2 4 Changing Magnification
44. he Lox message window Contact an SM or PEEM scientist for assistance 15 Step 6 Beamline Specific Set up SM Beamline Starting assumptions e PEEM is ready to image on and running e Beamline and photon shutters are closed e The manual valve between the PEEM and the M4PEEM tank is closed e The PEEM column valve is closed 1 Find the SM control computer located to the left of the PEEM microscope 2 Run the program runPEEM and runSM short cut should appear on one of the many linux screens The following window should appear for runP EEM X 101D 1SMBeamline PEEM Branch Control System ox 10ID 1 SMBeamline PEEM Branch Control 2 9 GeV Pressure before PEEM 1 El al 3176 10 1 Branch amp Grating Selection SelectBranch mr 1 160e 09 Torr Sec 2 il EE 1153 10 000 Gap b6 9084 220 3760 SelectGrating Q1 p 0000 o i OpenBeamline amp Branch ee SSH SHOSEDY PSH GLOSED gsH closeny 92 762280 Ahi OPEN CLOSE M os ooo ROH Energy Selection Sec 4 El EMI 1367e 090 Sec 6 M Mj 8 082e 10 000 Sec 7 igi I 9 000e 00 oo Sec 6 ial I 4940e 10 000 i Sec 9 m iil 5 005e 10 000 sec 10 El i 4 097e 10 cee i Sec 11 il E 16746 10 000 MONOCHROMATOR Miror 40013 81 40014 07 I Sec 12 El 8561e 10 000 Pa 8 823e 10 Grating 54616 19 54616 16 Sec 13 12366 09 Contacts EE 12360 Chithra 341 0400 cell sen EE 5 454 10 000
45. he transfer lens Previously the column valve was used in October 2008 the column valve was replaced by a new assembly consisting of a column valve and apertures the apertures should be used for this step Position this aperture so it partly blocks the image If necessary adjust the field lens current FL to bring the edge of this valve in focus When the microscope currents are properly adjusted the edge of this lens will be in sharp focus Recheck objective lens focus Step 7 Ensure Alignment of Planes in Microscope Toggle the SEL lens Minimize image motion by adjusting the acceleration lens AccL Stop toggle and refocus with FL Verify that the selected area aperture is still in focus 44 Step 8 Align transfer lens TL Establish the centre of the transfer lens as the optical axis e Select a fiducial feature a characteristic point like feature of your sample and move it to the centre of the image with the manipulator X Y e Toggle the TL current if necessary adjust wobble amplitude and frequency to make this motion clear on the Lox screen e Adjust the manipulator X Y until the fiducial feature is stationary coincident with the centre of the wobble Figure 6 1 The image should breath around the fiducial marker e f necessary use P1AX or P1AY to keep the fiducial point and the centre of the wobble motion in the field of view If this is not sufficient also use P3AX and P3AY e Turn off TL wobble
46. holder Putting the sample onto the transfer arm o Insert the first pin of the transfer arm into the puck o Slightly compress the spring on the end of transfer arm by gently pressing the transfer arm against the sample puck While doing this rotate the end of the transfer arm by 90 degrees until the second pin is engaged onto the slots on the sample holder o Use as little compression as you can get away with o The sample should now be engaged on the end of the sample holder Removing the sample from the transfer arm reverse of above Loading the Sample from the transfer rod onto the Manipulator O Be careful that the sample does not hit the mu metal shield when moving it into place You will need to retract the PEEM sample manipulator slightly to do this Slide the sample into the end of the manipulator there are top bottom slots which must be aligned up down and in out When the sample is engaged onto the manipulator holder there is a click and the spring at the top of the manipulator holder changes position O Press in slightly too much and the magnetic coupling will dis engage and rotate the end of the sample transfer rod by 90 to disengage the pins of the transfer rod from the sample puck Retract the transfer arm slowly Rotate the transfer rod by 90 and make sure that the pins do not hit the mu metal shield Make sure the end of the transfer arm is visible in the load lock before closing the valve to the main chamber
47. image Hints e Cut down the size of the image or use binning If the stack is too big it will be tedious to manipulate but contain little additional information 2 5 3 Recording Spectra e The process is the same as acquiring spectra see above except that only data from the regions of interest is saved This is chosen by unselecting save images e Don t use this mode save the image sequence instead You may want to process the data to extract a signal from a different region or look at an image acquired at a specific energy Seriously Don t let this be a I told you so Hard drives are cheap 3 2 5 4 XPS Image Sequences Exit slit in Refocusing selected Image isn t at a constant energy 23 Objective Focus Current Variation with Start Voltage 1700 3 term polynomial fit KotK X KoX en 1690 we E Ko 1666 2 z K 0 39089 ne a 2 K 0 0014188 o0 5 1680 lt O i i oD ae AObj is the value that needs to be added Pod _o to the objective lens current 1670 oo 0 O o AObj Ki K2 X X 0 amp 2 ra where X is the start voltage O O 1660 Red spots are for sample farther from objective lens 1650 T T T T T T T T 0 20 40 60 80 100 120 140 160 Start Voltage V The image focus depends both on the potential between the sample and the objective lens and the objective lens current When you records XPS images you change the potential and the image focus changes
48. in via Stephen Urquhart 28 3 1 2 Getting Started With Lox Running Lox 1 Before running Lox insure that the CaPeRS camera computer is connected to the CLS network Turn on voltages magnet supplies etc as outlined in the CaPeRS manual Ensure the PCO camera is turned on Run Leem2000 on the PEEM control computer Wait till it is fully active and the microscope is ready To run Lox double click on the front panel icon labeled Lox When you open Lox you will see the main window as shown bellow Z The LOX that goes Ping File View Setup Help Ring Current 169 28mA x Display E P 060519006 060519006 Current File Name N fe fe 3 Spectra Display VA Intensity cts Main Image display Spectra Region Of Interest a101 75 280 Energy eV Acquire Single Image Acquire Spectra Stack a Contrast eV os a Offset 1000 2000 BL Feedback On EutSitFolow Tian DO oof ao Go _Setup_ hee Image Ege Guatias Goniroles219 f Horizontal Defl mrad 0 000 1000 Go AG Bie A Setup t Signal Setup Entance SR un T5 Go ete AA EIA ERA 765625 Exit Slits Number of Signals to Aqui Dispetsive tum 100 00 100 Go Auto B C constant or on click Lie 3 16 37 The i acquisition was aborted Cannot start continuous image 4 NonDispersive um acquisition The camera is currently in continuous acquisition mode pa Go aouier 3 16 40 Video acquisition start
49. ion time The maximum safe value in the histogram is shown by a pink bar which changes location according to your dwell setting Signal Setup Signals to acquire during acquisition are listed here This control also appears in the acquire form see page10 for a full description 30 Communications Active Indicator 380 07 m col o Four Variable Fields Beamline Control This set of controls on a light brown background allows various beamline parameters to the desired values The Beamline name in the top left corner should correspond to the Beamline on which CaPeRS is presently operating If not you will need to reset the communications using the beamline setup window Those controls that are grayed out are not available on the defined beamline Each control operates in a similar manner To set a beamline parameter to a specific value e g to change the photon energy to 300 eV input the desired value into the white box and then click on the Go button The text on the Go button will change to and it will gray out When the movement is complete the new value should be displayed in the value display gray box to the left of the white input box and the button should be restored to its active state Values in this box are typically updated every 2 5s as PEEM Active Indicator Three Variable Fields PEEM Controls This set of controls allows the user to set PEEM variables from the LOX front panel The specific v
50. ize here what types of heating can be done from the computer and from the front panel Cooling A gravity feed system can be used to pass liquid Nz through the manipulator via the tubes on the side Use a tube to recover the liquid No 4 3 Transfer into Preparation Chamber Samples are loaded into the preparation chamber with a special titanium screw attachment marked inside a pink square on the Elmitec sample holder This attachment is mounted opposite to the bayonet attachment side User has to be very careful while transferring the sample to and from the preparation chamber The port aligner on which the og long transfer arm is mounted helps to perfectly c x I align the transfer arm axis with that of the sample Preparation i screw gt This is very crucial step for the smooth transfer transfer tip Sample holder 40 5 5 1 Frequently asked questions Why can t turn on the High Voltage The power to the HV rack is interlocked in several different ways If the high voltage power supplies 20 kV MCPs are not getting power the bakeout or pressure interlocks may have been tripped Check the vacuum in the mains and column Do not override these interlocks Don t If you still do not get power check 5 2 Breakers on the control rack 220 V if set to off would kill power to both racks enable switch on LEEM POWER CONTROL UNIT interlocks on enable switch bakeout and vacuum interlock switches on back
51. l fields of view it is better to make fine adjustments using both 45 positioners rather than the micrometer and one positioner e IF LOST A technique for finding the center of the vee Partially insert the contrast aperture vee until it partially obscures the image Decrease the transfer lens current until the contrast aperture V comes into focus on the screen Now it is easy to find the center of the vee as well as to see the burrs from machining on the edge of the vee Once centered it is easy to do the 2 6 turns and find the center of the aperture Step 18 Adjust Diffraction Stigmators Field Lens to Make Image Uniform Adjust the diffraction stigmators DSTIGA DSTIGB by e move TL current lower and higher than the value that give best illumination If the stigmators are adjusted correctly the illumination will remain approximately circular If they are not correct the illumination pattern will change from a horizontal line through a circle and to a vertical line Note the aperture must be in for this tuning to work 48 e Adjust DSTIGA and DSTIGB until the variation of the TL gives an approximately circular illumination with only size changing NOTE The MCPs always impose an intensity gradient getting brighter from lower left to upper right due to the orientation of the channels Take this into account when setting the most uniform illumination e Adjust FL current to focus the image NOTE If you are
52. mage e Note that you can not use the zone of least confusion to align samples that have very high contrast between adjacent sample areas or for samples with a lot of topography These effects will appear to distort the focus spot shape and you may misalign the sample For example the etched alignment test sample has sufficient topography to make this alignment problematic To align the sample tilt in these instances toggle the objective lens current and center the breathing motion on your fiducial by using four tilt screws on the manipulator Step 11 Insert Contrast Aperture Insert contrast aperture and adjust for optimum position 20 e Move aperture in until it starts to clip then use only ONE of the 45 positioner to optimize lateral position The lateral position should be such that the electron signal tracks cleanly along the motion axis of the aperture rod without clipping e Move aperture farther in until there is no signal Adjust the Lox image scaling to see the no signal background e Insert the aperture another 2 7 turns There is a vee notch followed by a 100 70 and 50 micron aperture each separated by 2 6 turns on the micrometer motion e When you find some signal adjust the micrometer drive and a 45 positioner to maximize image intensity The chromatic aberration is reduced and thus the spatial resolution is highest with the smallest aperture cuts off axis rays but there is an intensity penalty Images made wit
53. nment Find a small bright and isolated feature and adjust the objective lens current to focus If the feature is fuzzy then the sample may be badly misaligned see next step Step 10 Tilt adjustment Method 1 Non uniformly Illuminated Sample When the beamspot is on the similar size scale as the PEEM field of view the zone of least confusion of the objective lens method 2 is uneven and can not be used for aligning the sample tilt When the sample is tilted surface normal not aligned along transfer lens axis features in the sample will track left to right up to down etc when the sample voltage is changed relative to 20 000 V If the sample tilt is aligned perfectly a well defined feature will go in and out of focus with the change in the sample focus but the center of this feature will not move To determine the tilt axis that needs changing compare the track direction of a feature on the Lox screen as you adjust the sample voltage with the sample axis Note that the image on the Lox screen rotates with magnification e g a horizontal sample motion with the manipulator can result in an image motion at a different angle e g vertical inclined etc One needs to adjust the tilt horizontal or vertical to reduce the motion on the Lox screen This is an iterative procedure often both tilt axes need to be changed When the sample tilt is well aligned small features will remain stationary in the image but go
54. on 0 o closed z 3 16 54 06051 9005 img written ID Following I On 1D Harmonic i z Closed E 3 18 24 vides acquisition Scared maues will not be saved BL Feedback On etup 3 22 58 Video acquisition stopped Esk Folow Gn 2 OMe ooo a0 Go E ue BR A Se z acquisition The camera is currently in continuous acquisition mode 3 16 40 Video acquisition started images will not be saved Setting Energy The screen should now show shot noise and hot spots from the MCP with a very low level of signal 54 cps You must have the camera running and Lox in video imaging before turning up the MCP voltages Any problems with the MCP operation will then be immediately apparent on the Lox screen before the on set of permanent damage 13 Step 4 Turn on Image Intensifier Power Supplies If the column chamber has been vented and baked since last operation of the image intensifier increase the image intensifier voltages slowly 100 V every five minutes e While watching the Lox camera screen in video mode 200 ms dwell turn on the image intensifier to operating voltage e ZNN ensure correct polarity Phosphor screen voltage always greater than MCP voltage voltage difference not to exceed 4 5 kV e Operating voltages o Phosphor screen operating voltage 5600 V o MCP operating voltage 1450 V Step 5 Enable Lox Beamline Communications These instructions may be specific for each beamline SGM SM and PGM 1
55. or 1 P1 to 1359 mA o Retarding lens RL to 7282 V o Inner Lens InL to 4333 V o Acceleration Lens AccL to 1152 V o Projector 2 P2 to 1190 mA o Projector 3 P3 to 2800 mA Step 4 Turn on the Hg arc lamp CAUTIONS First set the iris to a smaller setting Turn the Hg arc lamp The lamp will take a few minutes to come to full power Watch the Lox video screen as it does so Set the iris for the Hg lamp or slits apertures photon energy beamline so that the maximum image signal green bar graph in the histogram window is 800 with 85 ms dwell 12 Hz frames per second with 2x2 binning MCP voltage of 1450 V You may need to adjust the sample z position to move the sample into the beam 43 Step 5 Focus Objective lens adjust sample position for Obj 1675 mA in focus Find a feature on the sample a small particle for example that provides good contrast without excessive topography The particle should not cast a shadow for example Adjust the objective lens current OBJ and or the sample position to bring this feature into focus The optimal OBJ current for best imaging properties at 20 0 kV accelerating voltage is between 1650 1750 mA If the current is lower that 1650 mA move the sample slowly towards the objective and re focus in small steps until OBJ current is in the range 1650 1750 The ideal Objective lens current is 1675 mA which corresponds to an ideal sample objective lens distance of 2 mm
56. rred through the preparation chamber Only samples with impeccable UHV vacuum compatibility may be loaded into this chamber Unless explicitly authorized in writing the PEEM staff scientist must supervise all activities in the UHV preparation chamber Vacuum set points have been established to protect the vacuum in the main PEEM chamber and the imaging column The first set point for each chamber sounds a buzzer and the second set point is interlocked to the high voltage power supplies These set points are an essential protection and must not be changed Multichannelplate Conditions bees Settings ne Camera Signal Contrast 0 0 0 5 1 0 Dwell ms Tey ee Saat yo Lon RS 0 eat tae ee ar eee Pa ey ear pa 200 a 175 391 Chart Brightness eT 1 0 0 0 1 0 1 z VEN a C A ET O E ID A aa A EET a E EA Oeil 9 765625 v Dark Correction Flat Field Auto B C constant or on click Lie 1 28 04 Error reciveing TCP r 1 28 14 Error reciveing TCP r 1 28 21 Error reciveing TCP r 1 28 27 Video acquisition stoppe 1 28 32 Video acquisition startec 1 28 36 Video acquisition stoppe 2 02 27 Video acquisition startec 2 07 38 Error reciveing TCP r Permanent damage is observed in the form of bright or dark spots on the MCP screen The bright spots are sometimes only active e g brighter when illuminated e g these channels regions amplify the el
57. rrently the Canadian Photoemission Research Spectromicroscope CaPeRS located at the Canadian Light source CLS The program has evolved from initial development and use at the Synchrotron Radiation Centre SRC Wisconsin to its current configuration at the CLS In conjunction with LEEM2000 the control program for the Elmitec PEEM it coordinates a variety of data acquisition tasks images signals from flux sensors temperature etc with control of the operation of several different CLS beamlines to form the top level user PEEM interface for CaPeRS This document is designed to guide novice users in use of the Lox program The appendix of this document deals with technical details for advanced users in particular the Beamline Setup form and the configuration file There are two other documents that may be useful for reference and to better understand the Lox program These are LoxProgrammersGuide doc a programmer s guide to Lox and Beamline Communication CLS doc describes the Beamline Communications Protocol Lox was written by Peter Hitchcock and Jacob Stewart Ornstein with encouragement and occasional direction from Stephen Urquhart and Adam Hitchcock The Lox TCP communications package and beamline control systems owes much to Tolek at the ALS for basic syntax and a number of people at the CLS for functionality Tony Wilson in particular Comments and bug reports on the software should be directed to Jacob Stewart Ornste
58. sieiscsiesennssessentisaiensasendcessushsaneasacesussssannaisundsasassadaneieaaad 42 6 1 PEEM Alignment Procedures advanced cccccceeeessseeeeeceeeeeeeeeeeeeeneeees 42 6 2 PEEM Start up Procedures advanced cccccceeeeeeeeseeeeeeeeeeeeeeeeeeeeeeees 51 1 Safety and Instrument Protection The first section outlines personal and instrument safety for the PEEM 1 1 Personal Safety The PEEM microscope operates with several high voltages including the sample manipulator 20 kV relative to ground the imaging energy analyzer 19 kV relative to ground the image intensifier and multichannelplates 5 6 kV and 1 4 kV the ion pumps 7 kV and titanium sublimation pumps 1 kV The high voltage rack LEEM III Power Supply Unit contains the electronics for the sample manipulator and imaging energy analyzer This cabinet is carefully interlocked The high voltage cables for the sample manipulator and the analyzer are special flexible cables with a nylon protective sheaf The titanium sublimation pump image intensifier and ion pump cables are thinner and also protected with a nylon or stainless steel sheaf These cables must be protected from kinks cuts abrasion or chemical attack If a cable is worn or broken contact the staff scientist immediately Electronics Contact Uday Lanke or Stephen Urquhart if any changes to the microscope electronics or vacuum system are required Vacuum and voltage interlocks must not
59. signal at the detector gets too strong Pay attention to the image displayed particularly when making ANY change to a magnet current or microscope control Reduce the light on the sample to keep the signals from saturation The upper limit should be 800 while in rapid view mode e g 85 100 ms image Step 1 Turn on Electronics and Computer Software The following starting conditions are assumed e The sample is in microscope 3 mm back from objective lens For alignment it is advised to start with a clean high contrast test sample such as the SiO mesh sample or silicon don t etch of the native oxide the work function of clean Si is greater than the energy from the Hg arc lamp Evaporating lead onto silicon is an effective way to increase the signal Strong signal and high contrast is essential for the fine tuning needed to get high spatial resolution e Make sure all power supplies lenses MCP sample high voltage are receiving power turn on the camera Turn up the sample high voltage to 20 kV Note increase this high voltage slowly and listen for discharges The pressure will rise in the main chamber as you raise this voltage e Turn on LEEM2000 software on the computer wait for the lenses currents to ramp up Select 100 micron FOV e Turn on Lox software on the computer start video rate imaging in Lox 200 ms dwell sliding average 2x2 binning Step 2 Turn on Image Intensifier Voltages Watch for Excessive Exposur
60. surfaces increasing the carbon dip Particulates can also migrate and deposit on the optics Image distortion can occur when non conducting particles are deposited on PEEM objective lens or contrast apertures When severe the microscope can become inoperable Please ensure that your samples are free from dust are stable under high voltage and that the load lock procedures are followed closely The microscope operates at high voltages Damaging electrical discharges can occur if the pressure gets too high A pressure interlock will shut off these high voltages when the pressure exceeds certain safe values Do not over ride these interlocks Vacuum Rules PEEM imaging is only permitted when the main chamber pressure is below 5 x 10 torr e Samples that significantly outgas must not be run in the PEEM e The PEEM main chamber preparation chamber or load lock may not be used to degas samples e The imaging column containing the multichannelplates and phosphor screen must be run at strict ultrahigh vacuum conditions low 10 torr range The image column is separated from the main chamber by a valve The valve must be shut when any operation may occur in the main chamber that might endanger the column vacuum sample transfer etc This valve is known to leak The UHV preparation chamber has been constructed for STRICT UHV activities only The upstream loadlock has been designed to ensure that no dirty samples are transfe
61. t getting close try to find a feature on the sample a small particle for example that provides good contrast without excessive topography A feature with excessive topography will cast a shadow Adjust the objective lens current OBJ and or the sample position manipulator retraction to bring this feature into focus The optimal OBJ current for best imaging properties at 20 0 kV accelerating voltage is between 1650 1750 mA corresponding to 2 mm distance Insert the column valve to check that the edge of this valve is in focus see Step 7 for complete instructions Note that if the field lens FL current is not properly set it is possible to push the sample into the objective lens while tuning This is easily checked by inserting the column valve and ensuring that the valve edge is in focus Step 9 Rough Alignment Try to centre the sample in the PEEM field of view Normally the manipulator is high vertically when the sample is transferred from the load lock The purpose of this step is to align the PEEM sample into the center of the beamline spot This should be done with great care particularly if large movements are needed Generally when the PEEM is well aligned a small change in the sample manipulator distance and a small adjustment in the table tilt is needed to align the sample onto the beamspot Large table motions including rotations should be left to the beamline scientist as this can really mess up the PEEM alig
62. than 10 of total 4096 range of the CCD then long averaging will lead to digitization artefacts you are restricting the dynamic range of the CCD You can adjust the MCP voltage to increase the signal in the camera However above a certain value currently 1450 V this only amplifies the noise and does not improve image quality 2 5 1 Recording Single Images e Select photon energy Ensure that the beamline and undulator have reached their targets e Select dwell time and averaging Unless radiation damage is a concern the dwell time should be set to have the signal fill 50 of the 12 bit 4096 count dynamic range of the camera Averaging of this signal can be used to improve statistics e Click Acquire Single Image The image will automatically be saved 22 2 5 2 Recording Spectral Image Sequences e Click on Acquire Spectra Stack this will get you in a menu where you can define the energy range of the stack as well as regions of interest and other signals to save e Define a region of interest even if you don t use it afterwards this will give you something to look at on the screen e When you have defined your image sequence select save images to save the entire image sequence e Select go to first energy then start Before entering the image sequence you can cut down the size of your save image by using camera set up this will let you save a sub set of the image rather than the full
63. the beamline slits remove apertures or change the start voltage As noted above the column vacuum must be maintained in the low 10 torr range for proper MCP operation This is best protected by ensuring that the column valve is shut before performing risky vacuum activities in the main chamber Objective lens The objective lens is important for the focusing properties of the microscope A build up of contamination can occur on this lens leading to charging When moving samples be careful to NOT run the samples into the objective lens scratches must be avoided Sample Transfer There is considerable risk of messing up the vacuum when transferring the sample Before transferring samples Ensure that the valve between the PEEM and the beamline is shut Ensure that the column valve is shut Ensure that MCP screen voltages are turned to zero Ensure that the sample high voltage is turned to zero 2 Basic Instrument Operations This chamber is organized into the following sections 1 1 Mounting Samples Loading Samples Operating the PEEM Microscope PEEM Alignment Procedures advanced PEEM Start up Procedures advanced _ h l 1 OA fo 2 1 Mounting Samples There are two categories of sample holders heatable and non heatable If user is intending to use the preparation chamber then he she must mount a special titanium adaptor on the side of the sample holder This is meant for the double sided transfer
64. uges and to the bakeout controller When the pressure set points are exceeded or the bakeout is in process power to the HV power supply is shut off The HV power supply has the following switches or controls Front of control rack Power switch Interlock key Enable and reset key Drain current setting is typically 300 uA 10 on the dial is 1 mA When you first start to turn up the voltage keep the sample about 4 mm back from the objective lens Turn up the voltage slowly in particular if you have an imperfect crystal sample Watch for a pressure rise as the voltage is applied due to discharges and field emission The discharge along the ceramics has been enough to raise the pressure into the mid 9 s 51 A drain current above 350 uA indicates discharges on the ceramics in the manipulator or analyzer Maintenance is needed Step 3 Turn on Start LEEM2000 program on CaPeRS PEEM computer Click the icon labelled LEEM2000 If the program is in soft start mode all lens currents are cycled to the values left in the last version of the configuration file This cycling improves the reproducibility of the instrument as it ensures the iron core magnetic coils trace a similar hysteresis loop in approaching a given current value Stigmator and deflector currents are set to their previous values cycling is not needed since these are air core coils Step 4 Turn on Camera Turn on the rocker switch at the back of the PCO CCD c
65. ut file The state of these signals is shown in the control in the bottom right of the main window or the bottom left of the acquire window The status of signals can be modified in either place Loading and Saving Acquisition settings You can save your current acquisition settings to disk by clicking on the Save Acquisition button in the bottom left hand corner of the Acquire form This will save the scan data as a saf file which is saved in XML format with a path and name of your choosing To load previous acquisition settings click on the load acquisition button and select the saf file to load The Signal Settings Box This is where signals can be added removed or modified There are two primary types of signals Region Of Interest ROI and everything else ROls are different in that you cannot define them in the signal controls but must create them in the main window A ROI will integrate the intensities in a region of the image and display these intensities in the spectra graph and write them to a file To define a ROI first click on the Define ROI button in the main screen You can then left click on the Main image display region and you will see a line appear you can draw a polygon with this tool by left clicking to add points Right click when you are finished and the ROI will appear in the Signals box it will look like ROI 0 in the box bellow Other types of signals can be added by clicking on the combobox and selecting the signal
66. varying the sample e g by heating cooling or other effects that can vary the sample objective distance then it is better to use focusing the selected area aperture as the criteria for setting the correct FL current and then to use the OBJ current for sample focus Correct TL DstigA DstigB to get uniform and bright illumination Step 19 Insert Energy Selection Aperture e Insert first analyzer exit slit approximately 15 mm 5 turns in from open position e Adjust P1 value to get most uniform illumination brightness Step 20 Double Check Column Alignment if Necessary If first you don t succeed try try again Step 21 Objective Stigmators The objective stigmators are important at higher magnification The stigmator values are a property of the microscope and are not to be changed These values are OSTIGA 0 OSTIGB 18 Step 22 Field Limiting Aperture e For better energy resolution if needed insert field limiting aperture Choose the aperture that fits best to your desired field of view e If imaging the dispersive plane this aperture should also be inserted The selective area aperture is mounted on the other side of the column valve The various positions for this aperture are 0 mm Open 20 mm 1 aperture 1250 micron diameter 23 mm 2 aperture 400 micron diameter 25 mm 3 aperture 1000 micron diameter 49 Tests after zooming in e Apertures in just contrast remove energy filter slits O When removing
67. with the start voltage The figure shows the variation with start voltage To ensure an image is in focus us the equaqtion AObj K Ko X X where X is the start voltage and add this value to the objective lens current 2 5 5 Focus scans 2 5 6 Other Modes _ 24 2 6 Other issues 2 6 1 Image Correction Dark Noise Correction When dark noise correction is selected Lox first records an image with a start voltage of 400 eV at this voltage no electrons reach the multichannelplate and the image reflects the dark noise of the MCP and camera Lox then resets the start voltage to the previous value and records data For each image Lox subtracts the dark noise image from the data image Flat field correction Flat field correction is intended to remove the effect of imperfections dead spots hexagons from the MCP structure from PEEM images particularly images acquired with very low signal levels This is done by taking the ratio between a data image e g the nice image of your sample area and a flat field image e g an image that just reflects the response of the multichannelplate The challenge to flat field correction is obtaining a suitable flat field image If the camera is bumped then the alignment of the camera onto the multichannelplates will be displaced and flat field correction will create artefacts It is very important to e Ensure that you have recorded a recent flat field image and verify this before

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