[Hallc_running] [New Logentry] Hall C Status

[mack at jlab.org]

Logentry Text:
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Status: other than Peter B's charge-symmetric background measurement (which has been completed), we are back to running elastics.

Notables from the last 24 hours:

Clear elastic peak https://logbooks.jlab.org/entry/4219244 . Appears to be broader and at lower energy than for earlier elastic running, consistent with perhaps slow rad damage to the PbWO4. No biggy. 

Cool plot giving an idea of the elastic statistics collected, and the overlap of NPS calorimeter settings in Charles's run plan. https://logbooks.jlab.org/entry/4219304  *(see comment below)

We lost roughly half the Owl shift for data taking (and 1/3 of the nite for sleep lol) when communications were lost with iochlc2 . https://logbooks.jlab.org/entry/4219450   There's a network switch inside Hall C which should probably be moved to the maze. 

After a day of elastic data taking, Hao's nearly real-time update of calibration coefficients is here:  https://logbooks.jlab.org/entry/4219397 . His recommended new HV settings are here: https://logbooks.jlab.org/entry/4219624 . (Amazingly quick turnaround.)  

I forgot to mention this yesterday: Chandan noted there was a fairly strong pattern in the FR_x vs FR_y plots. https://logbooks.jlab.org/entry/4219320 Since then, it has evolved into somewhat stable weak "net" pattern which is superposed on a flat background. The hypothesis has almost been excluded that it is due to some recent kinematics-dependent bias, exacerbated by how quickly we sometimes take 50k events. I'll keep an eye on it, but it would be nice if an expert could check if one of the two raster frequencies needs to be tweaked by a few Hz.  

Plan for the next few days (while we await Charles's awesome short term schedule): 

Monday - Change from 5 pass to 4 pass for Hall C starts at 08:30. There will be a Wien angle change as well. The NPS calorimeter needs to move just a little, to 8-ish meters. Then we take more elastic calibrations over-nite.

Tuesday-  Beam studies. The NPS calorimeter needs to move back to 3m to resume physics production. 

Wednesday - Dave G gets to do his Moller polarimeter measurement. 

(Paul King will do a non-invasive IA scan in there somewhere.)

Longer term - Dave M and Christine P will do a bcm calibration 


*Comment: To the extent that one would expect a more uniform position distribution, I infer that the achieved cluster position resolution is only O(1)cm. Peter B mentioned to me a few weeks ago that the position reconstruction is weighted linearly in energy. The PrimEx collaboration achieved O(1)mm resolutions in their PbWO4 sections with the more widely-used logarithmic weighting. But perhaps it's all good and I'm only getting confused by a strange ROOT plotting option. 

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This is a plain text email for clients that cannot display HTML.  The full logentry can be found online at https://logbooks.jlab.org/entry/4219649
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