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04/22/2004
Cell development:
- Todd (W&M):
- reported on the hybrid cell performance: with two lasers, the spin-exchange goes from 20.7 hours to 6.7 hours for oven temperature from 170C to 230C respectively.
- for comparison, good standard cell pumping with 3 lasers has a spin-exchange of about 8 hours.
Target lab:
- Ameya:
- Did an electronics inventory.
- Water calibration: adjusted the phase to get the signal in only one channel. Next will optimize the pick-up coils position.
- Lingyan:
- looking into optics parts to change laser polarization as fast as possible (for Transversity experiment).
Small Angle GDH:
- Vince:
- Did th_tg reconstruction for upstream foil.
- Tried to improve y_tg: higher order term didn't look to help.
- Tim:
- In kin. 10, several runs were taken when Q2L had the wrong polarity --> this explains the low rate.
Spin duality analysis:
- Patricia:
- E. Chudakov gave his estimate of the beam helicity ==> only 3 GeV data has to be flipped.
- removed runs with high charge asymmetry or "wierd" livetime.
- Study of the asymmetry behavior versus PID cuts for electrons: no big changes seen so far.
- Showed the pion asymmetries and asymmetries with no PID cuts: large pion asymmetries at 3GeV.
- Showed for the first time A1 and A2 for 3He.
04/15/2004
Cell development:
- Jaideep (UVA):
- Pieces of the new oven are done. Al is working on assembling them together.
- Study of EPR on hybrid cell. Principle: excit Potassium atoms and look at D2 light from Rubidium. Standard EPR works too but it is a lot noisier.
Target lab:
- Ameya:
- Computer problem is fixed.
- Water calibration: very noisy signal. Changing time constant on the Lock-In doesn't improve anything.
- Might come from the fact that the pick-up coils position were not optimized for water but for Helium cell.
- Jian-Ping:
- Discussed about the budget: one part is for the optical fibers and the cells. Now Jian-Ping would like to spend on electronics to have spares for all of them. And so when the laser room will be ready, we can have two systems operational.
Small Angle GDH:
- Vince:
- Made new cuts for sieve holes:
* used most recent database.
* kept loose momentum cut.
* made tight cut on holes.
- Optimized Y, THETA, PHI and offsets:
* increased number of events optimized (20 --> 50).
* th_tg looks much better.
* still problem with upstream foil. It is getting worse with momentum.
* ph_tg good, except central foil, central row.
* y_tg good, except central row, also central foil has a long tail.
* th_tg from upstream foil may have bad events from Be window, cut on ph_rot vs. y_rot will remove these events.
- To do:
* comparison of 4 momentum settings.
* apply cuts to exclude Be window events.
* dp optimization.
- Tim:
- Showed false asymmetries for kinematics 9, 10, 11 and 12
- Combined asymmetries for each kinematics for BHWP in and out: kin. 9 and 10 change signe with BHWP change but kin. 11 and 12 don't.
Spin duality analysis:
- Patricia:
- Study of PID cut effects on asymmetries:
* loosing the cuts doesn't have a real effect.
* tighting the cuts on cerenkov (1500 - More checks are under way.
04/08/2004
Cell development:
- Todd (W&M):
- Pulled off the 2nd 40cm-hybrid-cell.
- now it is spinning up.
Target lab:
- Ameya:
- LabView doesn't work==> come from the Operating System: need to upgrade.
- LabView 7 was installed but most of the VI don't work.
- Water signal on a sine wave background.
Small Angle GDH:
- Vince:
- Finished checking optimize code:
* target variables compared to ntuple value, comparable to 1E-5 level.
* optimized central foil +2% peak (sigma~2E-4): ideal value= -0.0202513, avg. value= -0.0202642 ==> avg. position is good.
* Yi is working on Hypernuclear: 12C FWHM ~ 2E-4 (1 peak).
- need to incorporate correction to dp_kin calculation (angle theta_scat, other approximations).
- Checking th_tg reconstruction: appeared worse after opening momentum cut and using unrastered runs.
Spin duality analysis:
- Patricia:
- Study of PID cut effects on asymmetries: didn't see noticeable changes after tightening the cuts ==> pion contamination is very small.
- Jian-Ping suggested to relax the cuts and look at the effect of pions on asymmetries.
04/01/2004
Cell development:
- Todd (W&M):
- About 10 hours lifetime for the first 40 cm hybrid cell.
- Jaideep (UVA):
- Did several spin-ups on the hybrid cell Panache with different oven temperatures and laser power ==> spin exchange more efficient with oven temperature increased and laser power added.
Target lab:
- Lingyan:
- Learning wall thickness procedure.
- Ameya:
- Starting water calibration.
- Heater broke.
- Will start to work on NMR frequency sweep after fixing computer problem (virus) and installing the new version of LabView.
Small Angle GDH:
- Vince:
- Looking at dp reconstruction: value in ntuple from ESPACE and value from optimization agree at a 1E-4 level.
- Theta_fp has discrapencies.
- Tim:
- Found a bug in his code.
- removed junk runs.
- kin 9: false asym= 16ppm, with good chi2
- kin 11 looks not so good but need some cleaning.
Spin duality analysis:
- Patricia:
- Changes made in ESPACE: make Bodo's subroutine for BPM/raster calibration active and put back sieve position for Duality.
- BPM/raster calibration for 1 GeV data is done.
- Asymmetry analysis checks:
1) check configuration for all runs by comparing Halog and runsheet entries ==> found several mistakes.
2) check target position to make sure it was Pol. 3He runs. (no mistake found)
3) check momentum settings. (no mistake found)
- Regenerated asymmetries:
1) after correcting the mistakes in the configuration.
2) after removing runs with all problems (DAQ crashed, ...) + step 1
3) after tighting cut on target windows + step 2 (before cut on ytg was +/- 0.065 and now it's +/- 0.050).
- Comments: 4 GeV asymmetries look to have the wrong sign --> need to look at spin precession versus energy.
- Plots: 3GeV-25deg, 4GeV-25deg, 5GeV-25deg, 5GeV-32deg.
- Jian-Ping suggested to check configurations in the middle of runs.
- Nilanga adviced to look at the behavior of the asymmetries with tigher PID cuts.
(last updated: 04/25/2004, maintained by Patricia Solvignon)