5 MeV Mott Polarization Measurement Procedure--DRAFT

Transcription

1 5 MeV Mott Polarization Measurement Procedure--DRAFT Document Number: Revision Number: Rev. 5; November 22, 2000 Technical Custodian:? Estimated Time to Perform: 20 minutes Procedure Overview This procedure provides the steps necessary for MCC operators to configure the 5 MeV Mott polarimeter system, make a polarization measurement, and analyze the results for comparison with polarization measurements made by the halls. The automated version of this procedure can be found by opening the Mott Measurement Procedure screen (monticello.adl => P-Gun=>Mott Measurement Procedure) and following the instructions provided. 1 This procedure is divided into sections as follows: Section 1.0 Setting Up Beam to the Mott Polarimeter on page 2 Section 2.0 Performing a 5 MeV Mott Polarization Measurement on page 4 Section 3.0 Backout Procedure on page 5 Section 4.0 Troubleshooting Tips on page 5 Prerequisites 1. Open the following screens before starting this procedure: a. PGun Ops Main (monticello.adl P-Gun PGun Ops Center) b. Mott Measurement Procedure (monticello.adl P-Gun Mott Measurement Procedure) c. Mott Expert Screen (monticello.adl P-Gun Mott Measurement Procedure Expert Screens Mott Expert Screen) d. Wien Filter Controls (monticello.adl P-Gun PGun Ops Center Related Screens: Wien Filter Controlsl) e. Pol Src Universal Bus Controls (monticello.adl P-Gun PSUB - PS Universal Bus proctemplate Page 1 of 6

2 f. Injector BPM Absolutes (monticello.adl=>bpm=>bpm Overview =>Injector Absolute) g. Correctors for the 0L Region (monticello.adl=>magnets=>magnet Commander=>0L=>0L Correctors) h. AES RF Captain - Injector (monticello.adl=>rf=>rf Status Commanders=>Injector=>AES Injector Commander) i. DTLite to make a multiple entry to ELog and Plog Procedure Steps 1.0 Setting Up Beam to the Mott Polarimeter CAUTION: Beam to the 5 MeV Mott dump must not exceed 20 A (CW) Insert the 45 MeV in-line dump. 2. Determine if the present Wien Filter Angle (spin) is acceptable: Wien Filter Angle = (Wien Filter High Voltage DAC Value / ) Is the spin >= 0, AND <= +30 degrees? ( 0 <= spin <= +30) YES: Use the 100keV Steering Script to change the Wien Filter Angle (spin) to +90 degrees before continuing this procedure. Is the spin <= 0, AND >= -30 degrees? (-30 <= spin <= 0) YES: Use the 100keV Steering Script to change the Wien Filter Angle (spin) to -90 degrees before continuing this procedure. 3. Record the original values of MBH0L01H,V and MBH0L02H,V. 4. Download the BLMs for Tune Mode running. 5. Ensure that masking is set up to run in the injector. 6. Establish ~10uA of tune beam to the 45 MeV in-line dump. 7. Use MBH0L01H and MBH0L01V to flatten (0.0 +/-.25mm) IPM0L02X/Y (abs). 8. Use MBH0L02H and MBH0L02V to flatten (0.0 +/-.25mm) IPM0L03X/Y (abs). 9. Set the Master Mode to Beam Sync Only. 10. Record the original phase of 0L Change the phase setting of 0L02-8 by -30 degrees (e.g., if the present value is -99.9, then the new value would be Establish ~10uA of tune beam to the 45MeV in-line dump. Keep IPM0L02X/Y(abs) and IPM0L03X/Y(abs) flat using MBH0L01H/V and MBH0L02H/V respectively. NOTE: It may be necessary perform Step in two increments of -15 degrees in order to keep the beam from tripping off. 13. Set the Master Mode to Beam Sync Only. Page 2 of 6

3 1 14. Record the present state of the prebuncher (i.e., ON or OFF) on the PGun Ops Main screen. 15. Set the prebuncher to OFF if it is presently ON. 16. Set the Current Conversion (under Calibration/Configuration Constants on the Mott Expert Screen) to Set the Current Conversion Offset (under Calibration/Configuration Constants on the Mott Expert Screen) to Turn off RF for 0L03 and 0L Set up the 5 MeV dipole as follows (Mott Expert Screen): a. Take the magnet offloop. b. Click on configuration #2 ( to the Mott ). c. Set the BDL Mode slider to 4026 G-cm. d. Put the magnet onloop to cycle. 20. Open the Mott Valve (VBV3D00A) on the Mott Expert Screen. 21. Set MFD3D00 and MFD3D01 (the Mott dump dipole) to 5.0 amps on the Mott Expert screen. 22. Set the polarimeter beamline correctors as follows (Mott Expert Screen): MBH3D00H = G-cm MBH3D00V = 90 G-cm 23. Insert the polarimeter beamline viewer ITV3D00 (Mott Expert Screen). 24. Insert FC#1 and change the beam mode to Viewer Limited. 25. Pull FC#1. Beam should appear on viewer ITV3D Using MBH3D00H & V, steer the beam to match Figure 1-1. Large steering adjustments shoud not be necessary. The beam does not have to match this view exactly; i.e., the beam does not have to be perfectly round, but it s orientation should be slightly to the right of the crosshairs as shown in this Figure 1-1 Figure 1-1: Nominal Beam Position on Mott Viewer, ITV3D00 NOTE: If large adjustments are needed, set the correctors back to the values in Step 22 on page 3 and use MBH1L01H/V to get the spot close, and fine tune using MBH3D00H & V. 27. Insert FC#1 and pull viewer ITV3D00. Page 3 of 6

4 28. Change the state of Target Ladder Video (IFL3D00) to IN. The light for this viewer can be controlled via the Mott Expert Screen. 29. Reset Target Ladder by changing the Mott Psub value to (Pol Src Universal Bus Control Screen) 30. Set target viewer by changing the Mott Psub value to Setup Viewer Limited beam to this target viewer and ensure that it appears at the location indicated by Figure 1-2. If necessary, use MBH3D00H, and MBH3D00V. 1 Figure 1-2: Target Viewer 32. Insert FC#1 and insert the 1um Mott foil by changing the Mott Psub value to Turn off the Mott Viewer Light. 34. Check that the BLMs are loaded for CW running. 35. Resume 5 A polarized (CW) beam to FC# Pull FC# Go to Section 2.0, below. 2.0 Performing a 5 MeV Mott Polarization Measurement 1. Set Measurement Mode to Auto-Stop (Mott Measurement Procedure Screen) 2. Set Auto-Start Duration to 30 seconds for a test run. (Mott Measurement Procedure Screen) 3. Click on the START button to begin the test polarization measurement. A yellow Active indicator will appear. 4. The detector energy spectra will appear on the Detector Plots (Mott Measurement Procedure Screen) The spectra should be similar to the example on the Mott Measurement Procedure screen. 5. Press the Continue Button under Run Controls on the Mott Measurement Procedure Screen. 6. Analyze the data by: a. Pushing the Analyze button on the Mott GUI (found by running the script on the Mott Measurement Procedure Screen) OR Page 4 of 6

5 b. Executing /cs/op/iocs/data/mott5/operations/analyze $file Where $file is the data file name found in the File Path field on the Mott Expert screen Data from the above script is put in /cs/op/iocs/data/mott5/operations/final.dat. 7. If any of the following occur, contact Injector On Call before continuing.: Quality factor is > 50. Suggested Run Time > 600 Polarization < 60% 8..Repeat steps 3-7 for as many Mott measurements as desired Backout Procedure 1. Insert FC#1. 2. Switch to Beam Sync.. 3. Close vacuum valve VBV3D00A (Mott Expert Screen). 4. Restore the 5 MeV Dipole configuration to #1 (this is the straight-ahead mode) and turn ON the Keep Magnet On Loop option. (Mott Expert Screen) 5. Return the prebuncher to its original state as recorded in Step 14 on page Set MFD3D00 and MFD3D01 (the Mott dump dipole) to 0.0 amps.(mott Measurement Procedure Screen) 7. Reset the polarimeter beamline correctors as follows (Mott Measurement Procedure Screen): MBH3D00H = 0.0 G-cm MBH3D00V = 0.0 G-cm 8. Restore the phase setting for 0L02-8 that were recorded in Step 10 on page Restore the original values for MBH0L01H & V and MBH0L02H & V that were recorded in Step 3 on page Pull the 45 MeV in-line dump. 11. The Mott measurements and the backout are now complete. Turn the beam back over to the scheduled program. 12. Make an elog and a plog of the Mott measurement results by pushing the Submit Elog button on the Mott Gui. 13. PROCEDURE COMPLETE. 4.0 Troubleshooting Tips NOTE: For the most current troubleshooting tips, push the Help button on the Mott gui. 1. Problem: Unable to steer beam onto desired positions on the viewer without railing allowed correctors Try: Put MBH3D00H and MBH3D00V back to the values in Step 22 on page 3 Page 5 of 6

6 Steer with MBH0L01H and V (these correctors adjust the launch into the Mott dipole) until the beam spot is close to the desired position. Then use MBH3D00H and MBH3D00V if necessary. 2. Problem: Beam polarization measurement is very small or the spectra do not look like the example. Try: Look at the TIME field under "Interpreted Scalar Data" on the Mott Meaurement Procedure Screen. If this number is not 0.5 +/- 0.1, cycle the NIM crate in the injector service building. 3. Problem: After backout, beam mode will not go higher than viewer limited Try: Reset the Mott target ladder by entering into Mott Psub field (PSUB-PS Universal Bus Screen) 4. Problem: Script continues to blow orbit up when steering. Try: Reinitializing the Mott matrix by pushing the "Initialize" button on the Mott gui. 5. Problem: Received a tcl error while while running script. Try: If available, press the "stack trace" button on the error box. Take a picture of the error (either with the elog, or "quickprint").record as much information as possible about what the script was doing when the error occurred. Pass this information and the stack trace along to Michele Joyce: erb@jlab.org. 6. Problem: Script continues to crash and physics program is being held up. Try: Paging Michele Joyce: Page 6 of 6