KLF beamline meeting - October 3, 2024

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Agenda

  • Announcements
  • KFM update (Mikhail)
  • Any other business

Minutes

Present: Igor, Richard, Hovanes, Vitaly, Pavel, Eugene, Mikhail, Tim, Josh, Beni, Richard, Sean, Marshall, Lubomir



  • Mikhail told us that the legal team at University of York will be working on the customs paperwork, probably with some customs broker. This is vacation time for them, so there will be a short delay in this activity.
  • Hovanes asked about the equipment for the hypernuclei station at the end of the kaon beamline as the gas systems (and probably some others) will most likely need to be reviewed before ERR-II by the lab for safety. Mikhail said that they need to provide detector cooling using liquid nitrogen.
  • Tim confirmed that if the cooling system qualifies as a pressure system, a long review will be needed (this is a standard process for JLAB).
  • Josh asked if it was possible to use ~155K nitrogen vapor instead of 77K nitrogen. Mikhail will check if it would be acceptable, but he though liquid nitrogen was necessary.
  • Mikhail will prepare some material for discussion.



  • Richard presented his studies of the rates in GlueX detector with different thicknesses of the tungsten absorber in KPT. In these studies, the target was empty, meaning that the target cell was present but was filled with "vacuum".
  • Richard considered tungsten thicknesses between 10cm and 20cm. The plug thickness was changed in very small increments using 1000 "simulation runs" with different thicknesses of tungsten (L=10cm+n*0.001cm, where n goes from 1 to 10000).
  • He simulated 5B gammas which corresponds to 1.2ms or nominal KLF beam time. He used x1000 scaling factor for phi-production, so the plots for kaons (or anything that comes from phi mesons) would correspond to 1.2 seconds of the nominal beam time. In the plots with rates , Richards scaled the rate axis to show the count numbers for 1.2ms.
  • Richard found that the K-long rates on the cry-target drops from roughly 2.5KHz to 1KHz when going from 10cm to 20cm tungsten plug. The dependence on the tungsten plug thickness is exponential , with an absorption length of 7.8cm for the plug which is in agreement with Eugene's calculations. Eugene pointed out that the attenuation of the K-long is somewhat involved and might not be modeled completely correctly neither in his calculations nor in GEANT4.
  • The kaons at the cryo-target seem to be mostly limited to the inside of the beam-pipe.
  • Richard saw decrease of the low energy gamma rates with increasing the tungsten plug. The rate with 10cm plug is 8KHz as he lowered the density of the tungsten plug to 16.5 g/cm^2. The absorption length for these low energy in the tungsten plug is 1.5cm, according to his plots, which which significantly longer than one radiation length for the tungsten-copper compound.
  • The thickness of the tungsten plug that will give us the low energy photon rate similar to GlueX-II is about 15.5cm. Lubomir pointed out that the beam diameters of KLF and GlueX are different (~6cm vs ~1cm) while the deadened wires for FDC are present in the diameters between ~2.6cm and 6cm.
  • Richard pointed out that the photons are not strongly peak at the center of the beamline, and there was a sharp edge where the beam-pipe starts. Mikhail asked if Richard knew where the "outside" gammas were coming from. Richard did not have a definite answer at that time.
  • Richard also estimated that the neutron absorption length in the plug is 8.3cm. The momentum spectrum was dominated by the low energy neutrons (~1MeV), according to Richard. This means that the neutrons are attenuated just a little slower than K-longs.
  • When looking at the SC rates vs Z at 10cm plug, there is a dominant peak at the downstream of the SC indicating that most of the hits come from the bent region of the SC. The SC rates at the 16cm tungsten plug should be acceptable for event reconstruction.
  • The CDC rates versus Z is mostly flat with 10cm plug, with a narrow bump at the upstream end.
  • Hovanes suggested to look at these rates vs Z plots for different thicknesses of the plug.
  • The SC hit rate falls with the tungsten plug thickness with an "effective absorption length" of 1.5cm, consistent with the absorption length of the low energy photons. Moskov thought that it would be good if we could increase the thickness of the plug to about 15cm and 16cm sacrificing half of the K-longs to be able to run in comfortable conditions.
  • The CDC ring 1 rates drop with the tungsten plug thickness was much slower, effective absorption length of about ~4cm(?) if fitted by a single exponential. But Richard pointed out that the dependence is really contains two exponential, where the steep one is similar to the one for low energy photons (λ=1.5cm) , and the shallow one looking more like the one for the neutrons (λ=8.3cm), or maybe something else. The reduction of the neutron rate at 16cm plug with respect to 10 cm plug was about x6.
  • Richard did not have time to measure the dependence of the rates on FDC, FCAL, BCAL, or TOF on the tungsten plug thickness. But the rates in FDC and TOF were very high.
  • Lubomir guess was that the rates will need to come down by a factor of x100 with respect to the 10cm plug in order for FDC to be operational. He would like to see simialr rates with GlueX=II conditions calculated by the same software to estimate the factor by which we need to reduce the rates.
  • Vitaly suggested to do these rate simulations without the start counter since he thought that the noses of the SC paddles that are in the beam create secondary particles that negatively affect the rates in the detectors.
  • Richard would like to improve the physics model his simulations. Currently muon conversions is not included in his simulations due to naming convention confusion since in high energy physics "muon conversions" is the conversion of a muon into electron/position pair. Richard also thinks that the production of high energy neutrons with photons is not well modeled in his GEANT4 program with his current selection of the physics list. He will work on this in parallel to the calculation of the rates with different beamline configurations. There was a brief discussion on the importance of the knowledge of the high momentum component of the neutron spectrum, without any conclusions.
  • Moskov thanked Richard for the important and impressive work that he has done so far, and encouraged him to continue working on the detector rate simulations.



  • Next meeting will be on October 10th.


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