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--- during_experiments [2017/06/17 14:46]
pereira [Shimming OBJ scintillator]
+++ during_experiments [2023/07/20 10:43] (current)
swartzj
@@ Line 4: / Line 4: @@
   * [[#Mask calibration]]
   * [[#Particle identification corrections]]
-  * [[#Handling detectors|Efficiency of OBJ scintillator]]
+  * [[#Efficiency of OBJ Scintillator]]
@@ Line 23: / Line 23: @@
   * Set the trigger to S800 singles and downscale factor 1
-  * On PanelMate, open page 4 in S800DRIV
+  <del>* On PanelMate, open page 4 in S800DRIV</del>
-  * Click on "upstream mask" and hit the "insert" button. This puts the mask in front of CRDC1
+  * On Diag_Main.opi, open Device Drives tab. The mask drive controls are at the bottom of this page in the Focal Plane section, namely RBT_BTS34:MSK_D2692 (Mask #1) and RBT_BTS34:MSK_D2703 (Mask #2).
+  * Click on Mask #1 (the upstream mask) and hit the "insert" button. This puts the mask in front of CRDC1
   * Start a run without taking to disk and look in the S800 SpecTcl at the 2D  xy position spectrum of (s800.fp.crdc1.x,s800.fp.crdc1.tac). If it starts to look like the spectrum shown below (the screenshot corresponds to mask 2, mask 1 looks inverted, in the sense of the triangle of dots pointing downwards), start taking data to disk until it has about the quality of the screenshot shown. If only a small fraction of the S800 focal plane is illuminated (dispersion-matched optics), consult with the S800 group to sweep the beam across the focal plane by changing the Brho of segment 8. The figure below shows the SpecTcl spectrum of the mask "shadow" measured in CRDC2 during a reaction setting.
@@ Line 31: / Line 33: @@
 {{:wiki:crdc2_56ti.jpg?550|Mask pattern measure in CRDC2 during a reaction setting.}}
-  * Remove the "upstream mask" with PanelMate
+  * Remove Mask #1 by pressing "Out".
-  * Repeat the procedure with CRDC2 by inserting the "downstream mask" on the same PanelMate page.
+  * Repeat the procedure with CRDC2 by inserting Mask #2 (the downstream mask) on the same diagnostics page.
   * {{:wiki:mask.pdf|Mask pattern}}
@@ Line 95: / Line 97: @@
-===== Handling detectors =====
+===== Efficiency of OBJ Scintillator =====
+At relatively high rates (~0.5 MHz), the OBJ scintillator will be gradually damaged. Experimenters should check the efficiency of this detector continuously during the course of the experiment. Whenever the rates drop below ~90%, they may request the Device/Beam Physicist to shim the detector.
+Before shimming, make sure that the thresholds are set properly (not too high) (refer to section "Object Scintillator Setup during [[Tuning the S800 (XDT)#Object scintillator setup|XDT]]"
-==== Efficiency of OBJ scintillator ====
+==== Shimming OBJ scintillator ====
 Shimming of the OBJ scintillator (or replacement) is required when the efficiency (measured by the experimenters) drops to about 85%. Please, refer to the operations [[https://docmgmt.nscl.msu.edu/share/page/site/NSCL/document-details?nodeRef=workspace://SpacesStore/cad088ca-6d41-4025-b010-8e620806a48b|guideline]] describing the procedure.

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