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tuning_the_s800_xdt [2015/10/26 14:09]
pereira [Coincidences] 		tuning_the_s800_xdt [2015/10/26 15:08]
pereira [Coincidences]
Line 214: Line 214:
  
 ==== Analysis line classic PPAC setup (Focus optics only) ==== ==== Analysis line classic PPAC setup (Focus optics only) ====
 +**THIS SECTION IS STILL IN PROGRESS**
  
   * "Classic" PPACs are the default detector, not TPPACs or CRDCs   * "Classic" PPACs are the default detector, not TPPACs or CRDCs
Line 237: Line 238:
  
 ==== Setting Optimization ==== ==== Setting Optimization ====
- 
-=== Focused optics === 
  
   * Expectations for A1900 FP to S800 FP transmission   * Expectations for A1900 FP to S800 FP transmission
Line 248: Line 247:
       * Want to balance losses between S800 analysis line and Transfer Hall (the S800 analysis line is typically slightly worse)       * Want to balance losses between S800 analysis line and Transfer Hall (the S800 analysis line is typically slightly worse)
       * Best diagnostic is scalers from S800 FP, object scintillator and XF scintillator       * Best diagnostic is scalers from S800 FP, object scintillator and XF scintillator
-      * Tweak y-quads (while watching scalers) in front of dipole gaps (this works both for Transfer Hall and analysis line); choose elements that have biggest effect with smallest ratio change+      * Using the knob box and the NCS application **QtKM** (file **BLSetup_A1900.gkm**), tweak y-quads (while watching scalers) in front of dipole gaps (this works both for Transfer Hall and analysis line); choose elements that have biggest effect with smallest ratio change
  
   * Document optimized transmission with another run to disk to measure rate of fragment of interest at S800 FP   * Document optimized transmission with another run to disk to measure rate of fragment of interest at S800 FP
Line 258: Line 257:
  
  
-===== Follow-up ===== 
  
-  * Before leaving beam with experimenters +====== Dispersion Matching Mode ======
-      * Set up current trip points on Linux HV controls +
-          * Values used for K-48 +
-              * 5 for CRDC and Ion Chamber anodes and intermediate image ppacs +
-              * 50 for CRDC drifts +
-              * 80 for IC drift +
-          * Ensure alarms are running +
-              * Make sure Linux HV GUI alarms are enabled +
-              * Make sure threshold on isobutane level is set up (not currently connected to alarms because they give too many false alarms when communication is lost) +
-          * All logs are being recorded +
-              * There is no log file for biases controlled by Labview +
-              * Linux HV +
-              * LabView gas handling system +
-              * Note in logbook +
-                  * Scintillator biases +
-                  * IC gate biases +
-          * Post reference printouts for experimenters +
-              * HV status: a snapshot of HV GUI +
-              * Gas handling system status: a snapshot of LabView window +
- +
-  * Create window configuration with summing regions to make it easier for experimenters to track efficiency/performance of all detectors +
- +
-  * Setting up coincidences for additional reaction settings in an experiment +
-      * Do not need to redo coincidence settup if secondary beam does not change +
-      * Might need to redo coincidence setup if secondary beam changes drastically +
- +
-  * To watch during experiment +
-      * Look for isobutene running out – messes up data over several hours +
- +
-  * Implementing dE- or TOF-based corrections is part of EXR  +
- +
-More detail needed +
- Minimum rates required for coincidence setup +
- Selection of appropriate substitute reactions for coincidence setup +
- How to feel comfortable that there will not be a problem with FP detector gases running out +
- Starting alarms +
- Starting logging +
- +
- +
- +
-====== Dispersion Matching tuning ======+
  
 In the dispersion-matching optics, the S800 focal point is achromatic, i.e. the position of the beam in the dispersive direction does not depend on the momentum. As a consequence, the beam is momentum-dispersed on the target area (pivot point) with a dispersion of about 10 cm/%. The main goal of the tuning is to ensure that the position and angle dispersion are cancelled at the focal plane, thus maximizing the resolution at that point. We also want a good image in the object position, which will also contribute to increase the resolution at the focal plane.  In the dispersion-matching optics, the S800 focal point is achromatic, i.e. the position of the beam in the dispersive direction does not depend on the momentum. As a consequence, the beam is momentum-dispersed on the target area (pivot point) with a dispersion of about 10 cm/%. The main goal of the tuning is to ensure that the position and angle dispersion are cancelled at the focal plane, thus maximizing the resolution at that point. We also want a good image in the object position, which will also contribute to increase the resolution at the focal plane. 
Line 360: Line 318:
               * What experimenters want (e.g., if they want singles, the cut has to be more restrictive to limit acquisition deadtime)               * What experimenters want (e.g., if they want singles, the cut has to be more restrictive to limit acquisition deadtime)
           * Move blocker, decrease attenuator, repeat           * Move blocker, decrease attenuator, repeat
 +
 +
 +
 +
 +
 +===== Coincidences =====
 +
 +  * Overview
 +      * Most experiments at the S800 involve setting up an auxiliary detector system (e.g. SeGA, HiRA, etc) to be used in coincidence with the standard detectors of the S800.
 +      * The auxiliary detector provides a secondary trigger that is fed into the S800 trigger system
 +      * A key part of setting up the S800 for such experiments is getting proper timing setup between the S800 and any auxiliary detectors
 +      * For cases where the Secondary detector has a slow response relative to the S800, the coincidence timing must be reset to the S800 timing by delaying the S800 trigger using the third gate and delay generator on the trigger GUI
 +          * A typical S800 delay for SeGA is 450 ns
 +          * Probably smaller typical S800 delay needed for HiRA
 +      * An example of experiments where auxiliary detectors are not used and, thus, setting up coincidence timing is not an issue are the experiments with tritons run by the charge exchange group
 +     
 +  * Choice of setting to be used for coincidence timing setup
 +      * The reaction of interest for the experiment can be used to setup coincidences only if the rate of coincidences is high enough
 +      * Sometime the pilot beam is used for setting up the coincidence timing in cases where the intensity of the secondary beam is too small
 +          * Example:  Reaction of interest 2p knockout to make Mg-36 from Si-38 (Si-38 rate was 1000 pps)
 +
 +  * Setup
 +      * Coincidence signals are usually visible on scope without running scope in acquire mode
 +      * Adjust the width of the early signal (S800 or secondary) should be wide enough to catch coincidences with the late signal (width of late signal is not critical)
 +      * Readjust TDC delays based on changes made to S800 trigger delay
 +      * Experimenters will need to adjust their delays based on delay made to S800 trigger
 +      * Have experimenters record a run with coincidences on their account
 +          * S800 trigger TDC channel should show a peak (which corresponds to coincidences)
 +          * "secondary" TDC channel should have a peak
 +              * This check is required for verification in cases of low beam intensity (e.g. 1000 pps)
 +          * Length of run required is typically about 10-15 minutes
 +          * To be resolved:  whether or not to this run copied from experiment account for documentation of device tuning
 +
 +  * Sample timing for running S800 with SeGA
 +      * SeGA trigger is late with respect to S800 trigger
 +      * The figure below represents a timing schematic to show how to
 +          * Setup of the S800 trigger to recover timing needed for proper functioning of S800 FP detectors
 +          * Set up the coincidence trigger
 +          * See:  http://groups.nscl.msu.edu/s800/Technical/Electronics/Electronics_frameset.htm
 +
 +{{:wiki:TimingSetup-schematics.jpg?500|Time setup schematics}}
 +
 +      * A double peak structure will appear in the TDC for the S800 trigger between the coincidence events and the singles events (see figure below); the groups are separated by 25 ns because of the delay introduced by the downscaler used for the singles
 +
 +{{:wiki:TimingSetup2-schematics.jpg?350|Double peak structure in TDC}}
 +
 +
 +
 +
 +
 +====== Follow-up ======
 +
 +  * Before leaving beam with experimenters
 +      * Set up current trip points on Linux HV controls
 +          * Values used for K-48
 +              * 5 for CRDC and Ion Chamber anodes and intermediate image ppacs
 +              * 50 for CRDC drifts
 +              * 80 for IC drift
 +          * Ensure alarms are running
 +              * Make sure Linux HV GUI alarms are enabled
 +              * Make sure threshold on isobutane level is set up (not currently connected to alarms because they give too many false alarms when communication is lost)
 +          * All logs are being recorded
 +              * There is no log file for biases controlled by Labview
 +              * Linux HV
 +              * LabView gas handling system
 +              * Note in logbook
 +                  * Scintillator biases
 +                  * IC gate biases
 +          * Post reference printouts for experimenters
 +              * HV status: a snapshot of HV GUI
 +              * Gas handling system status: a snapshot of LabView window
 +
 +  * Create window configuration with summing regions to make it easier for experimenters to track efficiency/performance of all detectors
 +
 +  * Setting up coincidences for additional reaction settings in an experiment
 +      * Do not need to redo coincidence settup if secondary beam does not change
 +      * Might need to redo coincidence setup if secondary beam changes drastically
 +
 +  * To watch during experiment
 +      * Look for isobutene running out – messes up data over several hours
 +
 +  * Implementing dE- or TOF-based corrections is part of EXR 
 +
 +More detail needed
 + Minimum rates required for coincidence setup
 + Selection of appropriate substitute reactions for coincidence setup
 + How to feel comfortable that there will not be a problem with FP detector gases running out
 + Starting alarms
 + Starting logging
 +
  
  
tuning_the_s800_xdt.txt · Last modified: 2023/09/22 15:15 by swartzj

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