Present: Chris Allgower, Andy Bacher, Jack Doskow, Ed Stephenson, Paul Pancella, Mark Pickar, John Schweitzer, Adam Smith
The meeting came to order at about 3:05 pm.
HARDWARE ISSUES
Jack Doskow will soon be finished with the 40 or so parts drawings needed for the internal pieces of the gas jet target. In most cases, these are more difficult to draw than to fabricate. The drawings will go to Walt Fox for approval early next week before going to the machine shop. The shop is already making parts for the target box weldment. A suitable mounting has been devised for the PSD of the luminosity monitor system, which views the target without obstructing the lead glass, and which accounts for cables and cooling lines. Jack has also received a wheeled cart on which the majority of the target can be assembled and tested.
Allgower reports he has made and tested the last of the long high voltage cables required for the lead glass array. We still need 100 more 130 ns long BNC signal cables made, and the whole bunch tested. John Schweitzer, a Hillsdale student who was just introduced to the group, is expecting to help with this task.
Andy received a report from Hermann that he has completed a revised calculation of the effect of a field clamp between the target box and the 6-degree magnet. With a 9" hole, and only two layers of steel (instead of 3) he predicts a residual field of only ~3 Gauss at the location of the nearest lead glass phototubes. This will make Tom Rinckel happy. With this data, we can now determine what kind of additional shielding needs to be applied to individual phototubes.
ANALYSIS OF TEST RUN
Pancella presented a first look at missing mass from the 3He data taken recently. The absolute calibration of the TDC scale seems to be far from what was predicted. If this is calibrated with the cone events themselves (assuming the pi0 kinematics) then a narrow peak appears at the correct (of course) mass value. This peak is roughly Gaussian, although it displays more tail on the lower mass side. With only one correction to the time in the first scintillator (based on distance from the single tube) the the Gaussian part of the distribution has a sigma of about 167 keV/c2. Evidence is also seen for momentum dispersion in the 6-degree magnet, which will have an effect on the calculation of the transverse component of the 3He momentum.
In the long run, it will probably be better to transform one or more of the kinematic distributions into the center of mass frame of reference in order to quantify our resolution. For example, perhaps the radius of the 3He momentum sphere in the cm would be best. It would then be necessary to plot the distributions resulting from 3He + 2 gamma the same way for comparison.
The meeting adjourned at around 4:15 pm.