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--- tuning_the_s800_xdt [2015/10/29 10:01]
pereira [Timing setup]
+++ tuning_the_s800_xdt [2015/10/29 11:26]
pereira [Timing setup]
@@ Line 166: / Line 166: @@
       * The three columns correspond to the **RF-FP** ToF (left), **OBJ-FP** (center), and **XFP-FP** (right)
       * The first (top) row corresponds to the Phillips TDC
-      * The second row corresponds to the MTDC with all the hits included. Note that in a unreacted-beam setting, the first hit typically provides the "good" ToF (i.e. start and stop signals come from the same event). This is not the case in a typical reaction setting, where the rates in the XFP or OBJ detectors are much higher than in the FP SCI
+      * The second row corresponds to the MTDC with all the hits included. Note that in a unreacted-beam setting, the first hit typically provides the "good" ToF (i.e. start and stop signals come from the same event)
       * The third row corresponds to the MTDC with only the first hit
       * The fourth row corresponds to the ORTEC TACs. Note that there is not **RF-FP TAC**
-      * The two spectra in the fifth row corresponds to the MTDC summary spectra of OBJ-FP and XFP-FP ToFs (zoomed in). The spectra show the ToF (vertical axis) vs. hit number (horizontal axis). In an unreacted setting, one expects to see the most of the "good" ToF peak recorded in the first hit
+      * The two spectra in the fifth row corresponds to the MTDC summary spectra of OBJ-FP and XFP-FP ToFs (zoomed in). The spectra show the ToF (vertical axis) vs. hit number (horizontal axis). Note that in a unreacted-beam setting, the first hit typically provides the "good" ToF (i.e. start and stop signals come from the same event). This is not the case in a reaction setting, where the rates in the XFP and OBJ detectors are much higher than in the FP SCI
       * An empty ToF spectrum means that either the delays are not right (and need to be adjusted) or the spectrum range is too narrow
       * The MTDC spectra should never be empty because the matching window is sufficiently wide (around 4000 ns)
@@ Line 181: / Line 182: @@
       * Adjust the TDC delays of E1 up, down using the Delay GUI
       * In principle, the TACs delays don't need to be adjusted
+  * Due to the MTDC has multi-hit capabilities. Let's assume that
+  * Now Let's imagine a situation where the rate from OBJ detector is much higher than from the FP detector. During this window, the MTDC will record one hit from the FP scintillator (which SpecTcl uses as the start ToF reference) and multiple hits from the OBJ scintillator (stops). As a results, we will have a series of OBJ-FP ToFs.
+  * Each of the ToFs from the MTDC has an array of parameters. For instance, for the OBJ-FP ToF, SpecTcl assigns an array of parameters s800.fp.vmetdc.obj.i, where i=0 stands for the first hit, i=2 second hit and so on.
+  * In an unreacted-beam setting at moderate rates, the first hit i=0 does typically correspond to the good ToF (start and stop come from the same event, as shown in the summary spectra above)
+  * This is not the case in a typical reaction setting, where there is a chance that earliest ToF hits

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