Present: Andy Bacher, Scott George, Mark Pickar, Tom Rinckel, Adam Smith, and Ed Stephenson
Tom Rinckel reported that the parts for the target box are now together and waiting on the shop to begin welding. Previous shop work on the liquid hydrogen target has been lowered in priority, but most of the shop crew is helping this week with p-therapy construction. The drawings for the magnetic shield have been sent to Walt Fox who will order the plates cut to size. Internal parts for the target box are partially completed. Jack still needs to finish the detailed drawings for the Pb-glass stands. We are about one month away from being ready to put the target box into the Cooler. After welding, we need a thorough leak-check, mounting of windows, etc.
Adam Smith has been installing a replay version of the CSB software on his computer. He is starting to look at contributions to the time-of-flight resolution. For cuts on the center of the sphere in XY-1, he finds a best result of sigma = 0.43 ns (12.6 channels and 29 channels/ns) comparing delta-E-1 against the mean timed ends of delta-E-2. A number of suggestions were made of things to investigate for contributions to the resolution.
Scott George (REU) reported on problems with the coordinate system conventions in Turtle. The coordinate system is referred to a ray that does not include energy loss, so energy loss followed by a bending magnet will always steer the particles off the center axis. Transport does not have this problem.
Mark Pickar continued to discuss his efforts to get the magnetic fields in his GEANT simulation more in accord with the channel as built. He has included edge effects on the quads, and has included an algorithm to consider distortions brought about by unequal spacing between the pole tips of the quadrupoles. These effects are visible on XY-3 only when multiple scattering is neglected. Otherwise, you get large Gaussian-like peaks. The widths do not indicate that we need to enlarge the delta-E-2 scintillator. Transmission losses through the system with multiple scattering included are less than 5% with present quads and detectors.
Mark also investigated the question of moving the final detectors downstream to lengthen the time-of-flight path. This will reduce the effects of path length differences in the channel on missing mass reconstruction, but you will need larger scintillators. The consideration of this option should wait until we know more about the limitations on time-of-flight resolution.
Mark next plans to generate a version of the channel response for the p+d -> 3He+pi0 case from the test run to compare with the data.
We discussed some issues for the future:
John Olmsted has accepted a post-doctoral position here and will be starting September 19.