Present: Chris Allgower, Andy Bacher, Scott George, Paul Pancella, Jack Rappaport, Mark Pickar, Adam Smith
The meeting came to order at 3:10 pm
Scott George reported on detailed Transport and Turtle calculations of the magnetic channel for dd -> alpha pi0. In particular, he has investigated profiles of the alpha cone at various points, and observed some puzzling drifts in the centroid of the distributions. The cone loses its left-right mirror symmetry after the septum magnet, in a way that qualitatively matches what was observed during the 3He test run ("egg" shape on WC2). Turtle predicts that the center of the x distribution is off by ~2 cm at the end of the channel, with much less drift in y. The vertical steering seems to be related to the hexapole components in the quads, but it is a fairly small effect, and most pronounced in Q1 (with a net upward drift).
Pickar presented results of his current GEANT simulation, also for the dd -> alpha pi0 case. He has developed models of the bending magnet fields using mapping data and comparisons with Turtle. The egg shape at WC2 is reproduced and clearly understood as due to the rather severe curvature of the field boundary at the entrance to the septum magnet. Work is still progressing on modeling the quadrupole fringe fields. It seems that neither Turtle, Transport, nor GEANT has yet simulated the pronounced vertical displacement (downward) that was observed during the test run, but none has yet looked at 3He, either.
Allgower reports that the mu-metal required to shield the lead glass phototubes has been ordered. Further research has revealed that the CAEN delay module we hoped to use cannot serve our purpose. It is an active delayed pulse generator and the maximum width it can produce is not sufficient. It is hoped instead that we can borrow two of the LeCroy modules from Fermilab or Brookhaven.
The meeting adjourned at 4:30 pm.