[Hallc_running] [New Logentry] Wednesday RC update for Hall C

[mack at jlab.org]

Logentry Text:
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The last 24 hours was a mix of critical measurements for the upcoming physics program, as well as data taking to improve understanding of the SHMS and HMS optics. Hall C has gone to controlled access so Dave Meekins can cool the target. In parallel, Simon et al will try to get the 3C arc power supply back to the standard 12 GeV project cycling procedure.* 

The plan is to finally start the high power cryotarget program on swing shift: lumi scans on LH2 and carbon, and elastic scattering on LH2. Then on to LT separations in 1H(e,e'pi+)n . The pass change will be delayed until at least FriSatday; the PD said it's too early to set the date and wants to see how much progress we make. 

TUE DAY shift we got beam back and resumed a low target power program.  After briefly establishing 70 muA with a rastered beam and no target , the crew switched to a carbon target and finished the HMS pointing scan while the SHMS was taking elastics. Using those SHMS data, the field integral of which has been absolutely calibrated over the last few years using the 3C arc measurements with the correct cycling procedure, Mark Jones concluded the true beam energy is 2.749 GeV or about 1% lower than the recent 3C arc measurement. https://logbooks.jlab.org/entry/3693519 
 
TUE SWING shift attempted another beam energy measurement, the intention being to use the correct 12 GeV project cycling procedure. This failed because the power supply couldn't produce enough voltage. Simon et al are looking into it today. The crew then began BCM calibrations. 

WED OWL finished the BCM calibrations that were begun on swing.  They then began an SHMS delta scan using the carbon elastic peak. Good progress was made, but the measurements were interrupted when we took the beam away to go to controlled access. 

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* The cycling procedure was altered for the summer run. Our Hall C measurement uses look-up tables for field integrals based on the 12 GeV project cycling procedure. It's not clear to me how large the impact will be, but it's great Jay and Mike T and now Simon et al are trying to get the 3C arc beam energy measurement system back to spec. 

 

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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/3694112
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