Present: Chris Allgower, Andy Bacher, Georg Berg, Hermann Nann, Tom Rinckel, Ed Stephenson
TARGET BOX DESIGN
Jack Doskow thinks he is mostly done with the changes suggested by Walt Fox. Tom Rinckel will review the drawings; there appear to be a few small changes needed. Internal baffles are not yet drawn. The plan is to go out for bid on the 6 box sides and 2 frames. The welding will be done in-house.
MULTIWIRE PROPORTIONAL CHAMBERS
The MWPC's are essentially ready to go. Enough parts were made for there to be two each of MWPC-1 and 2. We are using a pre-existing chamber for MWPC-3. Alan Eads has constructed one each of MWPC-1 and 2. The spares are not yet made, and at this point have low priority. Spare MWPC-1 is done except for connectors on the outside.
Doug Bilodeau has plateaued each chamber using an electron source. The scheme consisted of a thin scintillator on each side of the MWPC. Electrons from the source triggered both scintillators in coincidence. Between the two scintillators, two MWPC cards worth of wires were connected to a 2277 readout. Doug recorded efficiency as a function of voltage. The chamber gas was a mixture of 50% Ar and 50& isobutane, with trace alcohol added.
On MWPC-1 there are X and Y planes with 64 wires each and 2-mm wire spacing. The voltage at half efficiency for both planes is 2420 V. The U plane is separately biased. It has 2.82-mm spacing and 64 wires. It's half efficiency point is 2100 V. The connectors for U are placed so that the first two read in one direction and the second two read in the opposite direction. It was decided to correct this problem in cabling to allow for clusterized readout in PCOS-III.
On MWPC-2 the X-plane has 96 wires and the Y-plane 64 wires. Each plane is 2-mm wire spacing. The half efficiency voltages are 2400 V for X and 2380 V for Y. These overlap well the voltages for X and Y in MWPC-1.
The MWPC-3 is a large square chamber with 4-mm spacing and 160 wires in each direction. Plateau curves were run in the middle and at the edge of each plane. The half efficiency voltages are about 2300 V for X and 2340 V for Y.
Operation of the chambers was discussed. It was decided that we will dim the chambers during Cooler fill. There will also be an alarm circuit for the gas flow.
MAGNETIC CHANNEL
Tom has taken advantage of Cooler access this week to install the septum magnet on the mapper stand. The plan will be to work day and evenings to speed up mapping. This time, the exit end will be mapped first to look in new places for anomalies.
The vacuum pipe has been drawn, and we hope to have it out of the shop by the end of next week. Frames are also ready to hold the windows on the ends of the septum vacuum box. We will need to pressure test the final 12-inch window for the vacuum pipe exit before it is installed.
ELECTRONICS
The loan agreement with Fermilab was finalized at the end of last week. Chris Allgower brought back the electronics from Chicago on Monday. We now have in place everything we think now that we will need for the run, except for some signal and patch cables.
THEORY
Andy reminded people that there will be a theory workshop at the Theory Institute in Seattle on August 23-25 (Thursday-Saturday). The purpose is to discuss the feasibility and methodology needed to make a calculation of the charge symmetry breaking for this reaction using chiral perturbation theory techniques.
Ed has talked with Anders Gardestig about the angular distribution of gammas in the double radiative capture process. This needs to be revisited in simulation, since there may be some soft kinematic constraints that arise from a consideration of this that could be included in the analysis.
OTHER
The status of manpower recruiting was discussed.