Agenda

CPS & KPT design progress (Josh)
- Is the latest collimator cave/KPT layout approved so we can begin procurements?

Minutes

Present: Igor, Hovanes, Josh, Eugene, Pavel, Edy, Beni, Marshall, Vitaly, Sean

Pavel showed is recent simulations to optimize the beam deflection monitor.
Current conceptual design consists of two main components sitting just upstream of CPS entrance:
1. a copper ring with 0.5mm depth and 0.5mm width, and IR=4.5mm and OR=5.5mm
2. a set of four PMT-based counters around the beam pipe with a glass puck mounted on them for Cerenkov light production, plus some shielding around them.
He simulated offsets of 0mm, 0.5mm, 1.0mm and 2.0mm. The setup show pretty good sensitivity to 1mm beam shifts: the counter in the direction of the shift see x5 increase in the counting rates.
A narrow beam (FWHM=2.0mm insted of FWHM=2.8mm) reduces the counting rate, and also would reduce the sensitivity of these device to the beam excursions. Therefore, beam width needs to be monitored independently using regular wire scans.
Radiation dose rates created by this setup with nominal beam conditions are similar to what is present at the sides of CPS (10 rad/hr).
Eugene asked if the magnetic fields present in this area would affect sensitivity of the detector if the main source of the signal are low energy electrons. This has not been investigated.
Hovanes pointed out that the closest magnet is the CPS magnet, and next closest magnet is the GlueX quad just upstream of the tagger magnet.

Hovanes showed his calculations in an attempt to estimate the impact of the bleedthrough present in the out-of-time bunches coming every 4ns. He assumed that at 5μA beam current there will be 5nA out-of-time beam current. Note, that during GlueX we see about 2-3nA bleedthrough when running at 350nA. He did not do Monte-Carlo simulations, instead he just calculated these analytically assuming momentum spectrum from Ilya's simulations.
The calculations showed that these bunches separated by 4ns would show up low reconstructed (<2 GeV) momentum and low reconstructed W (<2.5GeV). Therefore, the event selection should be used to get rid of the background that could produce false bumps in W-spectrum.
Hovanes suggested that it would be good if the physics channels that are being analyzed come up with an estimated of the bleedthrough that they can tolerate without impacting physics conclusions.
There was suggestion from Eugene how the K+ momentum cuts in the event selections could reduce the background from out-of-time bunches.
We had to cut this discussion short to cover the remaining items on the agenda.

Josh reported that the CPS magnet design is nearly complete and the PR will be issued in a week or so.
KPT engineering design is complete (assuming there is no need for photon beam in the hall). Hovanes asked collaboration leadership to take a look at the final design before large procurements start. Igor agreed to take a look at the design and approve it or provide comments and suggestions with a week.
Eugene pointed out that changes to the KPT assembly needed for providing photon beam will not affect the procurement of some major items like beryllium, tungsten block, or the lead.
Josh said that the deadline for PR submission for this fiscal year is close, and we should not delay until next meeting because the timeline will be too tight. (added by Hovanes later: August 19, 2024 for purchases below $250K).