KLF beamline meeting - September 6, 2024

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Agenda

  • Announcements
  • Engineering design progress (Tim)
  • Any other business
    • Hall D model for RadCon (Igor)

Minutes

Present: Igor, Eugene, Hovanes, Moskov, Vitaly, Tim, Beni, Sean, Sashi, Pavel, Richard, Marshall



  • There was an Intermediate Readiness Review last week for KLF during which physics analysis related topics were addressed. Members of KLF presented 12 talks to respond to the items listed in the charge of the review committee. We already received 12 recommendations that will need to be addressed by the next readiness review (ERR-2). The full report with the recommendations as well as the findings and comments will be released in a couple of weeks.
  • Hovanes announced that procurements for KPT have been temporarily suspended until all related concerns are addressed and the engineering design is modified if needed. Igor was disappointed by this decision as he thought that the KPT design was in a good shape. Eugene pointed out that due to the budget cuts the procurements at Jefferson Lab are currently limited to the items that are absolutely needed for near term operations. Procurement requests for items over $250 will need justified by the requester and then approved by the Physics Division.



  • Hovanes presented the six recommendations that he though were related to the beamline group. The beamline group will need to provide an input regarding the beamline design. Most of the uncertainties at this time were in the design of the beamline in the collimator cave and downstream which affect the kaon, neutron and low energy photon rates in the hall. These design parameters need to be finalized and then implemented in the beamline and the detector simulation software packages. The main part of the response to the review comments will be addressed at the KLF analysis meetings chaired by Sean.
  • Addressing the review comment about 128ns bunching, Moskov said that he plans to present a stronger physics case for the 128ns beam bunching to be presented to Patrizia.
  • Moskov also stated that KLF intends to build a new Start Counter. Eugene warned us that the design and construction status for this new detector will need to well advanced during the next ERR-2 in order to be able to get approved for installations. The next ERR-2 would need to happen sometime next summer for the KLF installations to be approved for the summer of 2026, meaning that the time for the design and construction of the new Start Counter is short.



  • Richard showed his recent simulations of the GlueX detector response to the nominal KLF beam with the current design of the collimator cave. His plots correspond to 1.2ms of 5μA electron beam. This would mean that the low energy photon rate at the cryo-target is about 4.5 GHz.
  • Start Counter paddles are expected to see 0.4 hits per 64ns bunch burst per counter. This corresponds to 12 SC hits per bunch. With 16MHz bunch rate, this would amount to 6.4 MHz counting rate per SC paddle. This is pretty high rate.
  • The CDC and FDC seem to have pretty large occupancies as well. CDC is expected to see one hit per 64ns burst , and FDC is expected to see 4 to 6 hits per FDC layer. This could cause problems to tracking efficiencies especially considering the long pulse length distribution for CDC. Some of the drift chambers could even be unable to hold voltage at these level of occupancies, according to Richard.
  • BCAL occupancies look better, the hit number distribution versus the layer number suggests that most of the hits over thresholds come from the target area. BCAL occupancy per 64ns bunch is not high, below 2 hits for whole layer. FCAL (which did not include new ECAL) also has low occupancy.
  • Some of the TOF are expected to see 1 hit per 64ns bunch burst creating high background. This can be a problem not only for the rates but also for the PMTs as raising the thresholds will not help with the drawn anode current.
  • Beni suggest using a Lexan sheet to protect the TOF counters. Richard would like a volunteer to place one in the GlueX geometry.
  • Eugene suggested to repeat the same simulations with an empty target to see if the high rates in CDC and TOF come from the target or the beam halo. Richard will also to try to identify the origin of the hits from the output files.
  • The current version of the GEANT4 model of the KPT assembly uses 90/10 tungsten/copper compound with a density of the tungsten of 19.2 g/cm. Hovanes suggested to reduce the tungsten density such that it matches Tim's number of approximately 16.5 g/cm density for the compound material. Tim checked his notes and said that the compound density can vary between 16.5 g/cm and 17 g/cm.
  • Igor asked Richard to summarize what he thinks are the main issues that need to be looked into. According to Richard the detectors that could cause KLF problems are SC (#1), DCs(#2), and TOF (#3).



  • Pavel showed the progress that he made with FLUKA simulations for KLF.
  • He is simulating CPS versions without the outer lead layer, reduced led layer to see what consequences this will have on the shielding against the residual radiation from activated iron and concrete. If one of these options are selected, the controlled access delays may get longer and some restriction may be imposed for the areas near CPS during the access. Pavel is working with the engineering group to find the optimal trade off.
  • Pavel also created a toy model for the collimator cave to simulate the kaon beam content and radiation environment in the hall.
  • In general, Pavel's results agrees well with previous simulations. AS for the photon rates, his results are in a better agreement with Richard's rates from GEANT4.
  • The low energy photon rate reaching the cryo-target is 1.6 GHz according to his simulations. The average energy of these photons is around 5 MeV. The spectrum seems to be similar shown by other simulations.
  • The neutron rates estimations show that 1 MeV neutron equivalent accumulation in 10000 beam hours does not exceed 10 cm near the target area. The distributions seem to be consistent with the plots shown in KPT document for ERR-1.
  • Using FLUKA internal physics models, Pavel also estimated rates of K-longs at the cryo-target. He estimated that we will see around 8 KHz of K-longs on the cryo-target. Although his kaon momentum spectrum is not very different from what we used for most of IERR event generators, the neutron rates at momentum is not consistent with the MCNP estimates presented in the KLF proposal. The simulations in the proposal (MCNP for neutrons and Pythia for kaons) show a factor 100 less neutrons at around energies of 5 GeV, while Pavel's simulations show only factor of 3 more kaons than neutrons. Pavel also pointed out that there was a similar inconsistency in the proposal itself where the plot showing experimental data show only a factor of 5 less neutron rate than kaon rate at 5 GeV.
  • It is not clear what physics is included in FLUKA for K-long production.
  • Eugene is working on a standalone simulation of the K-long production using Pythia to estimate the kaon rates that need to be considered in addition to the kaons resulted from phi-meson production.



  • Tim gave an update on the engineering design of KLF components. Things are moving along well, he thinks that for now there is not much schedule pressure for KPT, but if do not resume KPT procurements for a long time we may have problems with maintaining previous schedule. Final KPT engineering design is waiting for the results of the simulations.
  • Designers worked with Pavel on trying to simplify the design by either removing the outer lead layer or reducing it.
  • Josh reported that the CPS magnet procurement has been awarded to a company from New Hampshire. The magnet is expected to arrive in the spring of 2025 at which time we will start testing it and mapping the field.



  • Moskov suggested scheduling this meeting as a two-hour meeting since we have had a few meeting that went almost for two hours. Hovanes thought it would be better to meet weekly instead, still for one hour. Hovanes will create a poll to find the optimal meeting time for a weekly meeting before sending the announcement for the next meeting.
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