Minutes of Weekly Transversity On-site Meeting
[Mar 20, 2006 (Monday) at CEBAF B101 (9:30-10:10 am)]
Attendee:Xiaodong Jiang, Xiaofeng Zhu, Xin Qian, Brad Sawatzky, Huan Yao
Minutes written by Lingyan Zhu

1. Hall A floor plan for transversity experiment
   A. (drawing) More details were checked by Xiaodong and Al.
http://www.jlab.org/~jiang/pac29/transn/tech_issue/floor_plan/transv_config.jpg
   B. (wire chamber in front of BigBite) There is 7" space between 
the shielding of BigBite and target magnet. Xiaodong proposed to put a wire 
chamber there to have a better control of the BigBite optics.
   C. (target collimator) Xiaodong prefers to postpone the near-target 
collimator design until everything else is almost settled. 
He mentioned that the BigBite magnet itself is a collimator with 
opening matching the 40cm length of the target. 
http://www.jlab.org/~jiang/pac29/transn/tech_issue/floor_plan/transv_coil_clearance.jpg

2. Target Progress
   A. (temperature) For hybrid cell, the oven temperature need to be increased to 
255 (Gen)~270 degrees from 170 to achieve higher polarization. The existing oven 
seems to be fine for the higher temperature. But some supporting plastic 
material in contact with the oven should be changed. --Xiaofeng
   B. (temperature control) Xiaofeng and Aiden tuned the PID parameters for GEN
and reduced the temperature oscillation.
http://www.jlab.org/~adaq/halog/html/0603_archive/060302225321.html
   C. (target log book) Xiaofeng set up the the target log book. They were currently
work on oven temperature control with different oven airflow and PID parameters.
http://hallaweb.jlab.org/physics/experiments/he3/target/html/logdir.html
   D. (others) Brad mentioned that there is some discoloring with the Gen target.

3. BigBite Progress 
   A.(possible BigBite shielding) Xiaodong proposed to add some shielding in the 
very upper and lower part of the  BigBite that is not used for production data. 
Xin did a Geant simulation for 500 MeV particles and confirmed that 
there is some space on the lower part of the BigBite that is not useful, 
referring to 
http://www.jlab.org/~jiang/pac29/transn/tech_issue/bbmaget_collimator/tran500.ps
   B.(singles rates) Xin analyzed some Gen data with 7 uA beam and obtained 
the rate of 17 MHZ for the BigBite wire chamber, which is consistent with the
previous simulation (12 MHz with 5 uA beam) and significantly higher than that
got by Gen (7MHz). 
   C.(wire chamber efficiency) Xiaodong mentioned that the efficiency 
for each plane of Gen wire chambers is around 90\%. He suggested we need to
looked into more details and estimated the tracking efficiency. Brad mentioned that
Gen has some low luminosity runs that will help.
   D.(TDC test) Brad was testing the CAEN TDC in the EEL building, that had problem 
with beam during the Gen experiment. 
   E.(electronics) Xiaodong is able to locate enough LeCroy 1877 TDCs 
for a half-system test setup. He will also check to see if we can get two 
sets of FastBus crates and power supplies.
He mentioned that the requiring preamplifiers may already been ordered by Doug.
   F.(space) The original space of the BigBite in the testlab was taken 
by a scattering chamber. --Xiaodong.
   G.(optical beam test) It is possible that the one-shift optical beam test 
may be carried out in the beginning of May. It will be in the same setting 
as the Gen production run except shifting the BigBite detector package backward 
from 1.0m to 1.5m. -- Xiaodong.

4. Trigger System 
   A. (coincidence) The Gen coincidence problem was resolved 
(few coincidence events with coincidence trigger). It was mostly due to the 
software cut (on event_type) that should not be there. 
Brad also mentioned that we should better not to use the trigger supervisor 
to determine the timing of coincidence trigger. It is hard to understand the 
timing with this programmable logic unit.

4. News
   A. Jen-Chieh Peng and David Howell from UIUC are at Jlab (for about a week), 
working on target coil design and Gen shifts. David is a potential thesis student 
of Transversity experiment.
   B. Transversity Collaboration meeting is coming on Apr. 11, 
joint with the polarized he3 meeting on Apr. 10.