Present: Andy Bacher Anders Gardestig Hermann Nann Tom Rinckel Ed Stephenson
SHUDOWN PREPARATIONS
The first quadrupole was tested at 300 A to determine whether there was any damage from the overheating experience. All voltage drops appeared to be normal and there is no known reason not to plan to use this magnet.
Two new delta-E1 detectors will be made. One is a replacement of the first detector that warped during the magnet heating incident. It is 6" by 8". There is plenty of thin scintillator stock. So we will also make four smaller detectors, each one 4" by 4". The light guide will be constructed out of one piece of plastic that is flat at one end and folded to a 2-inch length at the other. The mounting scheme will be devised later, but will likely include a frame that holds all the detectors relative to one another so that the gaps are minimized. One change in the design is to mount the light guide at a small angle (in, not out, of the plane of the scintillator) so that interference with the beam pipe or quadrupole windings might be minimized. Details remain to be finalized.
A plan exists to make the cosmic ray trigger scintillators from existing detectors. The cross section of these long detectors is 1/4" by 4". Two detectors will have a length of 42" and another two will be 30". These will be cut an reglued. The job has been given to John Vanderwerp, who has passed the necessary drawing along to Walt Fox. We will use the existing light guides and phototubes from lab stock. There are still four phototubes from the original purchase that will be used for the segmented delta-E1 detector.
Welding has started on the target box. The shop still has some 50 parts to make for the internal structure. The plan is not to weld the large flange that mates to the 6-degree magnet box until the target box has been positioned and aligned. Then the flange will be tack welded in place and the box removed for final welding and leak checking.
Cleanup of the tagger/CSB area has been done in preparation for the disassembly of the tagger setup and the construction of the CSB target box and lead-glass array. The tagger starts running again next week.
TALKS
The commissioning of the polarized deuteron beam in the Cooler has been chosen as a poster for the Polarized Sources and Targets conference to be held at the Brown County Inn in October.
Ed Stephenson will talk at the upcoming workshop on this experiment to be held at the Institute for Nuclear Theory in Seattle at the University of Washington. Anders Gardestig will also present his calculations of the double radiative capture process.
Anders showed his latest calculations with the channel acceptance imposed on the Dalitz plot. Andy suggests that one additional plot would be the tensor analyzing power as a function of missing mass.
REPLAY
There was some discussion of the background 3He events from the replay. There could be two sources. One is a double radiative capture process similar in spirit to what Anders has calculated. From the diagram, it is hard to see that the momentum matching will be as favorable as it is for the deuteron+deuteron process. In addition, the observed cross section is only two orders of magnitude under the pi-0 production, much higher than one might expect from double radiative capture.
Another possibility is a (p,3He) reaction in the material of the Cooler, such as the vaccuum baffles. This could also depend on the presence of the target since the target heats the beam and increases the amount of flux lost onto the walls.
One way to differentiate may be to raytrace forward and try to form an image of the source.
GROUP MEETING
The next meeting will return to Thursday afternoon at 3:00 p.m.