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JeffersonLab / ArgonIssueTracker

Issue tracker for Ar(e.e'p)
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Look at BPM signals in Y-axis (probably needs calibrated) #14

Open HagueT-Work opened 7 years ago

HagueT-Work commented 7 years ago

Plots for Y BPM and Rasters do not look like good signals. Barak said that raster signal is consistent with clipping top of target (ie. beam not centered). Barak suggested plotting the raster with a cut on the clock trigger to investigate.

HagueT-Work commented 7 years ago

It would seem that the Argon target is not quite where we think it is with respect to beam centering. I spoke with Barak earlier today and he said that the plots with of the Raster Y current appear to be consistent with hitting the top of the target. The number of events with the raster current pushing the beam in the +Y direction is lower than in the -Y direction. It should be a roughly flat distribution over the current range. This can be explained by noting that the triggers would bias the counts towards hitting the target head on. If we only look at Clock triggers, we should see that the raster current is uniformly distributed. Run 360 only uses the clock trigger and verifies this. Looking back to when we centered the target. We were able to see the carbon hole and to direct the beam through the straw. Immediately after, we took run 178 with the Dummy target. The raster plots on this run look uniformly distributed, as they should. Following that, run 179 used the Argon target and we can see the dip in the +Y raster current counts. I then checked a few other runs. All recent Argon runs appear to have this problem. However, if we look at runs 373, 374, and 375 which use the Titanium, Carbon Foil, and Optics targets (respectively) I do not see any issues in the raster plots. It would seem that this issue is isolated to the Argon target and that the beam is hitting it higher than we think it should be.

HagueT-Work commented 7 years ago

I'll make a log entry in the morning, need to gather the plots for uploading.

ShujieL commented 7 years ago

We need a BPM pedestal run for calibration. See comment below: https://logbooks.jlab.org/comment/10531#comment-10531

HagueT-Work commented 7 years ago

The pedestal run has been taken. Now the BPM needs to be calibrated: https://logbooks.jlab.org/entry/3462599

HagueT-Work commented 7 years ago

I'm going to edit the title of this issue. My initial thought was that the BPM signal looking odd was related to the raster signal looking odd. The next step is to calibrate the BPM and see if the plots are fixed because of that. We are now convinced that the two phenomena are unrelated. As far as we can tell, the raster signal peculiarity is due to target density fluctuations because of changing temperatures when the beam turns on. There isn't anything that we can do about that.

jbane11 commented 7 years ago

BPM's have now new calibrations. There still exist some unexplained issues.