[PEPPo] Daily RC Report 6/1

[voutier at lpsc.in2p3.fr]

Daily RC Report

https://positron.jlab.org/wiki/index.php/Fri%2C_June_1%2C_2012_%28Voutier%29Daily RC  
Report

Beam

The beam energy was changed to 6.8 Mev/c to explore the possible  
improvement of the signal-to-noise ratio in the Compton polarimeter at  
a momentum collection of 4 MeV/c. This change was positive and we  
tested a higher momentum collection 5.5 MeV/c, within the range of the  
planned data. As expected, the coincidence rate was going down, but at  
a too low level (25 Hz) which cannot be compensated by a current  
increase, the later being limited by the vacuum load in the PEPPo  
region. The conclusion is that the small quality increase in the  
accidental rate does not justify to reduce the energy range capability  
of the experiment, and therefore we will run at the demonstrated  
highest possible beam energy for the e+ production, that is 7.9 MeV/c.

http://opsweb.acc.jlab.org/CSUEApps/elog/entry/1788997

Early this morning the beam energy was changed to 5.5 MeV/c to prepare  
for production running in electron, and at the end of the day shift  
everything was ready to start data production in electron mode.

Detectors

Annihilation detector measurements were also performed but were not as  
conclusive as yesterday. The several adjustements of the electronics  
read-out did not appear to improve the situation. New measurements  
with the previous settings are planned when we will go back to  
positron running.

Hardware

An acces is planned on monday to put close to the polarimeter the  
electrometer measuring the T2 cup current, this should improve the  
quality of the read-out.

The possibility of increasing the vacuum trip level in the PEPPo  
region is also investigated, as well as the capibility of increasing  
S2 solenoide current by changing the power supply, the later being a  
major work which is not expected to happen before we move in the  
swing/owl schedule.

Event

The CHL was down for about 3h.


Next 24 hours:

Friday, 6/1 - SWING SL=Alexandre CAMSONNE

   Mott measurement
   Measure the Compton asymmetry sensitivity to the electron  
polarization orientation

Saturday, 6/2 - OWL SL=Jean-Sebastien REAL

   Calibration of the polarimeter at 5.5 MeV/c
   Magnetization scan
   Target depolarization effects

Saturday, 6/2 - DAY, SL=Joe

   Calibration of the polarimeter at 3.2 MeV/c
   Calibration of the polarimeter at 4.2 MeV/c


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