Agenda

Minutes

Present: Pavel, Tim, Hovanes, Josh, Eugene, Vitaly, Sean, Moskov, Sashi, Beni, Lubomir, Richard, Mikhail, Marshall, Edy, Igal

Moskov announced that there will be an accelrator BTeam meeting on Tuesday, November 12th where KLF tests will be discussed. Moskov suggested that Hovanes attends it too.

Richard showed plots from his Jupiter notebook that can be accessed from JLAB by anyone with a JLAB account. He studied the ancestry of the particles that caused the hits by going back in the history of interactions all the way to KPT. Richard ignored all the hits that happened downstream of the beginning of the cryo-target refrigerator. At that z-location of the cryo-target refrigerator he drew a plane where he scored positions of the tracks that entered GlueX since he was going to ignore the hits of all the interactions that happened inside GlueX. In today's presentation Richard assumed a cylindrical start counter without a cone part.

Richard sees that most hits in cylindrical start counter (without the cone) are made by photons, followed by electrons. The origin of these particles are mostly in the tungsten plug or in the beam pipe walls in the section after the collimator cave. Electrons and positions are only coming from the beam-pipe, consistent with what Pavel sees. Photon come from both beampipe and KPT.

The hits of the particles causing SC background is almost always with R < 4cm, but at the position of the tracka crossing the plane at the LH2 target assembly the radius is larger, all the way to the beam pipe radius. Therefore, Richard thinks that using a shield wall in front of the target will help reducing the start counter hit rates. Richard thinks that it is easier to implement a wall than to shield the pipe, but he agrees that shielding the pipe the way Pavel suggested should work as well.

Richard also showed plots for CDC which indicate that most of the background in CDC come from the beam pipe. Therefore, either shielding wall in front of the target or shielding the beam pipe should work for CDC.

FDC hits seem to originate from the KPT. Shielding wall would not help FDC that much.

Hovanes and Lubomir asked about the hit rate in FDC with a 14cm plug versus wire number. Richard did not have that plot on-hand.

We were running out of time, so we did not go over FCAL and BCAL plots that Richard also had.

Answering Moskov question about the feasibility of the experiment with the existing GlueX start counter, Richard said that he thinks that we now know what causes the high hit rates and we know how they could be eliminated. His simulations and Pavel's simulation paint similar pictures. We still need to optimize the shielding to make the experiment possible. Richard thinks that if a new start counter is built, it needs to be cylindrical. Eugene also said that the cone area of the GlueX start counter may get damaged by the radiation, and it also needs to be evaluated. There was also an argument that cylindrical start counter would reduce the forward acceptance of the detector for some physics channel that could somewhat mitigated by a longer scintillator paddles.

There was a short discussion of weather the shielding wall or shielded beam-pipe would be easier to implement. Hovanes pointed out that these are not mutually exclusive, and both can be done. In addition, one could place a collimator in front of the pulsed tube refrigerator of the cryo-target. Hovanes also confirmed that the shielding wall present in Richard simulation cannot stay where it as it will interfere with KFM detectors.

The shielded pipe could start 2 meters downstream of the PS magnet in order not to interfere with KFM. It can extend to the start of the pulsed tube refrigerator of cryo-target. Modifications after the refrigerator flange would have to be coordinated with the target group.

Tim said that we already had shielding wall in front of the target cart (which is a couple of meters upstream of the refrigerator) for Primex with a transverse size of around 20cm.

Pavel would like to have drawings for KPT and the cave, PS magnet, and cryo-target in order to model the beamline in FLUKA.

Tim reported that because of the delayed procurements caused by freezing of capital spending, there could problems with making the installation schedule for summer of 2026.
He would need to start finishing the design of KPT in about a month, and he would need to know the conceptual design of KPT assembly. Tim will also need another designer with at least 50% time working on KLF, in addition to Keith's time.