Difference between revisions of "Beam Line Detectors Expert"

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(Adjust BP Voltages)
(Adjust BP Voltages)
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The power used by the Beam Profilers includes both High Voltages and Low Voltages. The high voltages are used to power the MaPMTs while the low voltages are used to power the pre-amplifiers.
 
The power used by the Beam Profilers includes both High Voltages and Low Voltages. The high voltages are used to power the MaPMTs while the low voltages are used to power the pre-amplifiers.
  
; High Voltage: Each MaPMT is powered by its own HV channel. Therefore there are eight channels for each plane. These HVs can be adjusted through '''HV X/Y''' → '''PVU/D: Show X/Y HV Channels'''. As the threshold for the discriminator is embedded in hardware, adjusting the HV is the way to effectively change the threshold for a group of channels using the same PMT unit. Normally, the shift personal should not change the high voltage on the beam profiler unless instructed to d so by the expert.  
+
; High Voltage: Each MaPMT is powered by its own HV channel. Therefore there are eight channels for each plane. These HVs can be adjusted through '''HV X/Y''' → '''PVU/D: Show X/Y HV Channels'''. As the threshold for the discriminator is embedded in hardware, adjusting the HV is the way to effectively change the threshold for a group of channels using the same PMT unit.  
  
; Low Voltage: Readouts from the same plane share two groups of Low Voltages. Each group needs two 5-V and one 1-V inputs. Always make sure that they are ON. No adjustment is allowed. In case of malfunctioning BPU, such as abnormally hot channel, the shft taker can turn off and turn back on the low voltage to check if the hot channels disappear. If not, the on-call expert needs to be contacted.
+
; Low Voltage: Readouts from the same plane share two groups of Low Voltages. Each group needs two 5-V and one 1-V inputs. Always make sure that they are ON. No adjustment is allowed. In case of malfunctioning BPU, such as abnormally hot channel, one can turn off and turn back on the low voltage to check if the hot channels disappear.
  
 
== Expert Personnel ==
 
== Expert Personnel ==

Revision as of 15:44, 24 February 2017

Active Collimator

Control and DAQ

The Active Collimator screens are here:

Main Action Bar -> Under "BEAM" select Monticello -> Select BPM -> Hall D Active Collimator Diagnostics (you may need to move the window to see the correct option as it tends to stretch onto another monitor)

The preamp gains, 1Hz data and averaging/digital gain are on that screen. Go to the Raw Wire Data button for the individual plots and Time Domain Graph HDACI/O for positions.

Changing preamp gains

Once Monticello is opened to the active collimator diagnostics page you'll be able to adjust the preamp gains. On the left side of the screen there should be two sets of 4 buttons labeled IAC5H01I Gains and IAC5H01O Gains. These are typically kept at 10E-10 A/V. To change these, click on one of the buttons and select a new gain setting.

  • Note: With increased radiator thickness and/or current, the preamp gains should go from 10E-10 A/V -> 10E-9 A/V and so on.

To determine if the preamps are saturated, look near the bottom left of the screen where it says IAC5H01L ADCs and IAC5H01O ADCs. If these numbers are approaching +/- 32k then the preamps are saturating.

Performing a collimator scan

The basic idea of the collimator scan is to move the collimator in X and Y and monitor counting rates some detectors in the hall behind the collimator to find the position of the collimator that allows largest intensity of the photon beam in the hall. For the collimator position we identify the response of the active collimator in terms of X and Y, assuming the Active Collimator is calibrated. Once these Active Collimator position is found, the collimator will be returned to its original position and request the beam to be placed at the AC position found. Since the Active Colimator is moving in this procedure and we want the beam to stay stable, the photon beam positions need to be locked using the Upstream Beam Profiler (BPU).

  1. Make sure that all beamline voltages are on by opening "Beamline Voltages" GUI from the main CSS menu.
  2. Insert BPU into the beam.
  3. Set the probper gains on AC. For a 2e-5 RL radiator and 50 or 100 nA beam, use the 10E-10 gain setting (current default) for the active collimator. If using a different combination of radiator and current, adjust the preamp gains to prevent saturation. See above for adjusting the gains. If you aren't sure, contact the active collimator expert.
  4. Ask MCC to centre the beam on the Upstrem Beam Profiler (BPU) at (x,y)=(0,0) (or whichever at that time is believed to be the best positions) and to turn the slow lock from AC to BPU.
  5. On the main CSS overview GUI, select "Motors" under the "Beam" section. This will open a new window.
  6. Select "Collimator". This will open the basic collimator motor GUI. Move the active collimator to the current hole position.
  7. Select "Collimator Scan GUI". This will open two GUIs (possibly right on top of each other), one is for X and second one for Y motion. These are coupled scans. The outer scan is the Y-scan, the inner scan is the X-scan. On the GUI called colim:scan:scan2 select the range and ste size for the x-motion, and in GUI called colim:scan:scan1 selct the the range and size for the y-motion. You may need to adjust some other scan parameters as well.
  8. Push blue "SCAN" button on the colim:scan:scan2 GUI to start the scan that controls the outer scan (in Y) and for each point in Y drives the X-scan.
  9. The start will continue and it will pause when beam is lost. The scan is done when you see "SCAN Complete" on top of the Y-scan GUI.
  10. To analyse the data click "Analyze Scan" button on any of the two GUIs. This will open ROOT GUI for the last scan. On the large GUI showing previews for all detectors used in the scan, chose one, for instance Active_Target and click on the "Analyze" button on the little pad next to it.
  11. Looking at the 2D plot of the rate versus collimator motor position identify the best positions.


Optimal transmission scans

  1. Move the active collimator to the current hole position
  2. For a 2e-5 RL radiator and 50 or 100 nA beam, use the 10E-10 gain setting (current default) for the active collimator. If using a different combination of radiator and current, adjust the preamp gains to prevent saturation. See above for adjusting the gains. If you aren't sure, contact the active collimator expert.
  3. Ask MCC to center the beam on the active collimator.
  4. Explain to MCC that an active collimator scan is in progress and the position will appear to drift significantly. Tell them not to adjust
  5. On the main CSS overview GUI, select "Motors" under the "Beam" section. This will open a new window
  6. Select "Collimator Scan GUI" AND "Collimator"
  7. In the "Collimator Scan GUI"
    1. Set the start value to be -116.700 and end at -106.700 for the 5.0 mm hole. Use -15.240 to -5.240 for the 3.4 mm hole.
    2. Set 0.5 mm steps
    3. Use a 10 s positioner settling time
  8. Once step 3 is complete and the scan GUI has been configured, in the "Collimator" GUI use the expert mode to move the colilmator to the furthest negative position for the scan (-116.7 or -15.240)
  9. Start the scan in the "Collimator Scan GUI" by clicking SCAN
  10. When the scan finishes use the "Collimator" GUI to move the collimator back to the nominal hole.
  11. As HDOPS, go to /home/hdops/active_col_scans and execute the MyaViewer_plotter script.
    1. This script will display the active target rate, the PS and PSC coincidence rates and the inner x position of the active collimator
    2. ./MyaViewer_plotter <begin> <end>, where <begin> and <end> are in YYYY-MM-DD HH:MM:SS format
    3. From the plot, find the maximum of the active target and coincidence rates and compare it to the x position of the active collimator.
    4. This will be the optimal x position for the active collimator
  12. To get the optimal y position, as MCC to move the beam vertically to 1 mm, 2mm, -1 mm, and -2 mm and record the active target and coincidence rates at each of these positions
  13. From the recorded rates determine the optimal y position.

Calibration scans

  1. Move the active collimator to the 5 mm hole
  2. For a 2e-5 RL radiator and 50 or 100 nA beam, use the 10E-10 gain setting for the active collimator. If using a different combination of radiator and current, adjust the preamp gains to prevent saturation. See above for adjusting the gains. If you aren't sure, contact the active collimator expert.
  3. Ask MCC to center the beam on the active collimator.
  4. Explain to MCC that an active collimator scan is in progress and the position will appear to drift significantly. Tell them not to adjust
  5. On the main CSS overview GUI, select "Motors" under the "Beam" section. This will open a new window
  6. Select "Collimator Scan GUI" AND "Collimator"
  7. In the "Collimator Scan GUI"
    1. Set the start value to be -139.999 and the end position to be -80
    2. Set 2 mm step size
    3. Use a 2 s positioner settling time
  8. Once step 3 is complete and the scan GUI has been configured, in the "Collimator" GUI use the expert mode to move the colilmator to -139.999
  9. Start the scan in the "Collimator Scan GUI" by clicking SCAN
  10. When the scan finishes use the "Collimator" GUI to move the collimator back to the 5 mm hole.
  11. If performing a 2-d scan
    1. Ask MCC to raise the beam vertically by 0.5 mm to 1 mm, depending on the study. Repeat the process to the positive and negative vertical limit.

MCC will eventually have a hard time to move the beam at the extremes at which point the scan in that direction is done.

High Speed ROOT File Writer

An EPICS IOC server is set up on gluon29.jlab.org:26064 to write the raw waveform data to /gluonraid1/Users/ac directory on demand.

The control of this High Speed DAQ can be found in Hall-D's EPICS GUI:

  1. Open Hall-D CSS EPICS Control if not already available following instructions
  2. From Main Action Bar, open Active Collimator GUI.
  3. Start or Stop the High Speed ROOT File by clicking the button underneath the title.
  4. Once started, make sure the a new ROOT file is created and the File Size is increasing.

In very rare occasions, e.g. some one rebooted the AC DAQ server, the writer IOC needs to be restarted

Reboot using command lines
  1. Log onto gluon29 using hdsys account
  2. telnet localhost 26064
  3. Restart the IOC by keyboard combination Ctrl+X
  4. Exit the IOC proServer by keyboard combination Ctrl+]
  5. Exit the telnet by typing quit

Raw Data Analyzer

From Active Collimator GUI
  1. Click the Analyzer button in the PXI Fast DAQ section.
From a Linux terminal
  1. log onto a gluon machine, e.g. gluon30.jlab.org, using account hdops: ssh -X hdops@gluon30
  2. enter acanalyzer directory: cd ~\acanalyzer
  3. start the analyzer script: ./run
  4. in the analyzer, open a collection of raw data files or a processed ROOT file and start the analysis.

List of EPICS PVs

How to move the active collimator between the 2 collimator holes

Before going into the hall:

  1. Call RadCon and have them come and survey the active collimator and surrounding area
  2. Move the collimator to the 3.4 mm hole position. This will allow access to the hole to use the alignment pin. There is a phone in the collimator cave to call someone to do this if you are already in the collimator cave. If you do not do this the beam profiler will prevent access to the 3.4 mm hole with the alignment pin.
  3. Wear EAR and EYE protection as there is vacuum and a thin window. Ear protection can be found in the counting house near the keybox.

In the hall:

  1. After rad con surveys the active collimator and surrounding area use the red-handled allen key sitting on top of the post-collimator beam line to unbolt the support bracket holding the active collimator to the collimator platform.
  2. Slide the active collimator and support bracket along the collimator platform to the other set of holes. The bolts should fall loosely into place.
  3. Before tightening the bolts, use the alignment pin to center the active collimator. This pin is located in a plastic bag on top of the post-collimator beam line, the same place the red-handled allen key was kept. For the 3.4 mm hole use the narrow end first and make sure the pin goes all the way in.
  4. While leaving the pin going through the active collimator and into the collimator, tighten the bolts.
  5. Once the bolts are tightened, remove and place the tools back on top of the post-collimator beam line.

Collimator and Radiators

Move Collimator

  1. Open Hall-D CSS EPICS Control, if not already available, following instructions.
  2. From Main Action Bar, click Motors in BEAM section.
  3. Click Collimator to bring up the Collimator Control GUI.
  4. Click the button corresponding to the desired location to move the collimator. Wait until the Motor is Done.
  5. If the communication to the motor is broken, e.g. pink fields showing, refer to instructions to reboot the IOC.
  6. Make a log entry to HDLOG.

Move Radiator

  1. Open Hall-D CSS EPICS Control, if not already available, following instructions.
  2. From Main Action Bar, click Motors in BEAM section.
  3. Click 'Amorphous' radiator to bring up the radiator Control GUI.
  4. Click the button corresponding to the desired location to move the radiator. Wait until the Motor is Done.
  5. If the communication to the motor is broken, e.g. pink fields showing, refer to instructions to reboot the IOC.
  6. Make a log entry to HDLOG.

Halo Counters

Radiator Harp Scan

Figure 1. GUI for opening various beamline-related controls screens.
Figure 2. Radiator wire scan control screen.

The radiator harp scan is performed to determine the electron beam profile in X- and Y-directions using two wires mounted on the same insertion device that holds the three amorphous radiator. The wires are mounted at ninety degrees to each other and are inserted into a beam by a stepper motor at 45 degrees with respect to the horizontal plane.

Open Radiator Wire Scan GUI

  1. On the Main Action Bar click on Motors button. A new screen will pop up showing various buttons for beamline related screens.
  2. On the newly open GUI (Fig. 1) click on Radiator Scan GUI button. This will open the radiator scan GUI (see Fig.2 ) that will be used for the radiator scan.


Preparing for Scan

  1. Ask MCC to take the beam away for a few minutes and let them now that we will remove all radiators from the beamline and that we will do harp scan at the radiator position.
  2. When the beam goes away, retract the amorphous radiator or the diamond radiator from the beam line. There should be no radiator in the electron beamline during the radiator wire scan. The goniometer can be put in BLANK position instead of RETRACTED.
  3. Request 100nA beam from MCC and ask them to mask the Ion Chamber and Hall D amorphous radiator motor from the Fast-Shutdown (FSD). Wait for the beam to come back and stabilize at the nominal positions on 5C11B BPM and start the scan.

Performing the Scan

  1. Push the blue SCAN button on the radiator scan GUI. The motor will move to the starting position for the scan and start going through the points and acquiring scaler data. The scan automatically pauses when beam goes away and resumes when the beam is detected again. The scan takes about 7 minutes without beam interruptions.
  2. Periodically check for the messages at the top of the radiator scan GUI. When the last point is acquired, a message Scan Complete will be shown and the motor will stop at that last position. Note that the motor for the radiator scan (and amorphous radiator) will not retract on his own, it will need to be retracted after we are happy with the scan results. If Scan Complete message does not appear on the top of the scan GUI but you are absolutely sure that both wires scanned the whole beam, you need to push ABORT button on the scan GUI. This will abort the rest of the scan and perform some necessary restoration steps. If you are not sure if the wires went through the beam, either wait for the Scan Complete message or call EPICS expert.

Analyzing Data

Figure 3. TOP GUI for selecting the wire scan file for analysis/fitting.
Figure 4. Overview GUI for selecting detector for analysis/fitting.
Figure 5. ROOT analysis GUI for fitting the x- (left) and y- (right) profiles. The fit results are shown in the fit parameter box. The units are in mm. The mean positions and the widths are in the horizontal and vertical direction, while the x-axis of the plot is the index of the stepper motor in mm-s.
  1. Once the scan is complete, push Analyze button on the bottom of the radiator scan GUI. This will open a xterm window, a small top window (Fig. 3) and an overview window (Fig. 4) that shows the response of various detectors versus the motor position of the scanner. The main feature of each detector plot is that there are two peaks at different position motors, one for x and the other one for y. If the peak is not visible for one detector that means that detector is not sensitive to having a wire through the beam and fitting that signal is pretty much useless. Note that the actual screen that shows up may be different from what is shown in Figure 3 since the number of enabled detectors in the scan can be different.
  2. Select the detector that shows the best signal (usually signal/background ratio is the best indicator) by clicking the corresponding Analyze button. This will open the screen with the fit of the signal. Usually the best once are those from HALO:T:electron:tag detectors. Note that one can open multiple detector views with the fit to compare. The new screen that pops out will show the results of the fit for the x-profile on the left panel and for the y-profile on the right panel. The x-axis of the histograms are the motor position in millimeters, while the fit results are the beam positions and width in the horizontal and vertical positions. The horizontal and vertical positions are related to the motor position by a simple factor of sqrt(2) from the scanner geometry. The vertical axis of the histograms are detected scaler rates from the selected detector.
  3. If the fit is good, make a log entry by clicking Make Log Entry button on the bottom of the screen. A small dialog box will pop-up for a comment, and after the comment is filled and Submit button is clicked a log entry will be made. It is a good idea to check the logbook to make sure that log entry has been submitted successfully.
  4. If the fit is not good, one can improve the fit. The points in the views are ROOT histograms, so one can right-click on the histogram points and bring up the fit-panel and improve the fit by selecting the initial values for the parameters and limits for the fit. Keep in mind that the x-mean and y-mean are not the same as the positions of the peaks on the horizontal axis of the shown histogram. Once the fit is satisfactory, a log entry should be made by clicking Make Log Entry button on the bottom of the screen.

Evaluating Results

We expect to see approximately Gaussian distributions of the beam intensity in both x- and y- directions similar to ones shown in Figure 3. The expected sigmas of the Gaussian distributions are expected to be approximately within 0.6mm to ~1.2mm. Distributions with sigma in either X- and Y- directions greater than 1.5mm is too wide and might cause problems at the diamond radiator. Note that narrow beam profiles do not mean better photon beam since the Hall D beamline was designed to have a wider beam spot at the radiator focusing at position of the primary collimator. An accelerator physicist will evaluate the result of this scan together with other scans upstream of the radiator to determine the conversion quality of the electron beam image at the converter. We also expect to not see any shoulders and halos around the Gaussian distributions above 10^-4 level in this wire scans. Whether the halo or the widths are not satisfactory and what actions need to be taken right after the scan depends on the instructions from the run coordinator.

Backout from scan

  1. From one of the ROOT analysis GUIs select File->Exit to close the ROOT screens if not needed anymore.
  2. Request the beam to be taken away for a minute.
  3. When the beam is off, insert the desired radiator in the beam, and retract the amorphous radiator if not using the amorphous radiator. Remember that the harp and the amorphous radiators are on the same insertion device.



Beam Profilers

There are two beam profilers installed in the beam line to measure photon beam profiles in front of the active collimator and right before the photon beam dump. Each profiler has two planes scintillator fibers to give X-Y 2D information. Each plane consists of 64 fibers of 2 mm width and they are readout by eight Multi-anode PMTs.

Open Beam Profiler GUI

  1. Open Hall-D CSS EPICS Control if not already available following instructions.
  2. From Main Action Bar, click Beam Profilers in BEAM section.

Check Scaler Rates

  1. Open the Upstream Profiler or the Downstream Profiler to check the rates.
  2. In the GUI, one will see the scaler counts plotted as a function of X and Y axises. The updating frequency is controlled by the DWEL parameter. The update interval is DWEL×256.
  3. There are three modes of data presentation and we are currently using two of them: Raw and Accumulative.
    • The Raw mode update the plot with the new counts coming from the most recent interval.
    • The Accumulative mode keeps the sum of all hits until the Reset button is pressed.
Figure 6. Beam profiler GUI.

Adjust BP Voltages

The power used by the Beam Profilers includes both High Voltages and Low Voltages. The high voltages are used to power the MaPMTs while the low voltages are used to power the pre-amplifiers.

High Voltage
Each MaPMT is powered by its own HV channel. Therefore there are eight channels for each plane. These HVs can be adjusted through HV X/YPVU/D: Show X/Y HV Channels. As the threshold for the discriminator is embedded in hardware, adjusting the HV is the way to effectively change the threshold for a group of channels using the same PMT unit.
Low Voltage
Readouts from the same plane share two groups of Low Voltages. Each group needs two 5-V and one 1-V inputs. Always make sure that they are ON. No adjustment is allowed. In case of malfunctioning BPU, such as abnormally hot channel, one can turn off and turn back on the low voltage to check if the hot channels disappear.

Expert Personnel

The individuals responsible for checking that the beamlineis ready to take data and setting its operating parameters are shown in following table. Problems with normal operation of the beamline instrumentation should be referred to those individuals and any changes to their settings must be approved by them. Additional experts may be trained by the system owner and their name and date added to this table.

Table: Expert personnel for the beamline instrumentation
Name Component Extension Date of qualification
Alex Barnes Active Collimator (570) 242-1844 June 4, 2014
Hovanes Egiyan BPU & TAC & GONI x5356 March 25, 2016
Alexandre Deur Beamline June 4, 2014