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--- tuning_the_s800_xdt [2015/10/26 14:07]
pereira [Setting up Reaction Settings]
+++ tuning_the_s800_xdt [2015/10/26 14:09]
pereira [Setting up Reaction Settings]
@@ Line 254: / Line 254: @@
-===== Reaction Setting =====
-==== 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
-      * It is not clear whether coincidence setup gets logged as “XDT” or “EXR”
-  * 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}}
@@ Line 375: / Line 332: @@
          * The two figures below show the spectrum **CRDC1.XG!FOI-AFP-BFP** before (top) and after (bottom) the dispersion-matching tuning for a typical experiment. Be aware that the width given by SpecTcl for the selected peak is not too reliable. It is more convenient to do a real gaussian fit. Unfortunatelly this is not an option included in the current version of SpecTcl. That's why some device physicists prefer SpecTk for this type of tuning
 {{:wiki:DispMatch-XG-run2.png?650|XG before tuning.}} {{:wiki:DispMatch-XG-run5.png?650|XG after tuning.}}
+====== Reaction Setting ======
+===== Setting up Reaction Settings ======
+  * Calculating reaction setting
+      * Center unreacted beam at S800 FP
+          * Adjust spectrograph Brho to center beam at S800 FP
+          * Requirements for a beam to be “Centered”
+              * Spectrograph dipoles matched
+              * Beam position within about 1 cm of center as judges by 0 point on crdc1x spectrum or on track.xfp spectrum
+          * Record run to disk to document centered unreacted beam setting
+      * Calculate reaction setting using “effective” beam energy and the nominal target thickness
+          * Ideally, experimenters should be the ones making this calculation
+          * This approach assumes that the target thickness is known
+  * Reaction setting to FP
+      * Start with Attenuator setting of unreacted beam and step up in intensity
+      * Set up beam blocker, if necessary
+          * Expect to see unreacted beam if reaction setting is within +/- 3% of unreacted beam setting
+          * Should have to move only one of the two blockers unless charge states are present
+          * A graphic tool is available to help (not yet calibrated)
+          * Try to cut only as much as necessary; depends on
+              * What rate limits allow
+              * 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
+===== 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
+      * It is not clear whether coincidence setup gets logged as “XDT” or “EXR”
+  * 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}}

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