KLF beamline meeting - September 26, 2024

Agenda

• Announcements

• Updates from FLUKA simulations (Pavel)

• Engineering design progress (Josh)

• KFM update (Mikhail)

• Any other business

Minutes

Present: Pavel, Hovanes, Vitaly, Igor, Moskov, Eugene, Richard, Edy, Lubomir, Mikhail, Sashi, Beni, Marshall

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• Hovanes announced that we sill not be able to use K-Long capital budget until February 2025. Eugene explained that this is related to SOLID funding and all capital budget procurements are suspended in the lab.

• Richard simulations with different lengths of tungsten blocker are about 90% complete.

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• Pavel has been studying the radiation background in the hall using his FLUKA model. He improved the shielding in his FLUKA model. The main goal of the core modification is to slow down and kill the forward flux of energetic particles in the cave, limiting the radiation in the hall.
• Pavel introduced new shielding collars around the beam pipe in the walls in the labyrinth and the collimator exit wall. The first CuW collimator is continuation of the dump with 5 cm dia hole in it, 8 cm outer radius. The next three CuW collimators have 4 inches outer radii and they tightly surround the steel beam pipe (switching from 2 to 2.5 inch OD after the magnet). The lead plugs in the walls are 12 inch radius.
• The model still does not have neither the pair spectrometer magnet material nor the magnetic field. Mikhail commented that the PS magnet itself can be considered pretty good shielding.
• Pavel also placed a plug right before the permanent magnet inside the beam pipe to attenuate low energy photons and neutrons. It consists of 5cm layer and 5cm borated poly layer.
• With the new shielding, Pavel sees that the radiations dose rate in the first section of the labyrinth is factor of x5 higher than without these extra shielding. The radiation environment in the hall is much better compared to the previous FLUKA model.
• Beni commented that it is very encouraging to see these improvements. Hovanes was less optimistic and he pointed out that the improvements are only with respect to the previous FLUKA model which lacked some of the features present in the engineering model and in Richard's GEANT model. These results do not directly apply to what Richard showed using his GEANT4 model, in Hovanes' opinion. Beni thought that Hovanes misunderstood his comments.
• Richard commented that, in his opinion, the new shielding does not have much advantage with respect to what Tim already has in the engineering model where there is pretty thick irons in the walls. Richard also pointed out that the elliptical beam pipe does not really limit the aperture for kaons impacting the cry-target. There seems to be disagreement between the size of that beampipe in Richard's model and Pavel's model. Richard also showed some plots from his GEANT4 simulations where there was no noticeable charge particle halo around the beampipe that could be seen on the linear scale. Richard expressed his surprise that the neutrons were so cleanly limited to the beampipe diameter in FLUKA calculations.
• The photon rate in the cry-target in the Pavel's new model is 420MHz, and the neutron rate on the target is 140KHz.
• With this shielding configuration, the kaon rate on the cryo-target is 4.6KHz now (vs 7.8KHz without the lead plug).
• Hovanes asked about the dose rate at the start counter location. Pavel does not have good statistics at this time, but based on his plots, the dose rate now is well below 30 mrem/hr which was the rate expected according to the PAC proposal.
• Beni pointed out that the start counter is not the only concern for KLF. FDC and CDC see extremely high rates, and also the FDC packages have more material in the beam for diameter above 2.6cm that can produce secondary particles creating background in the detectors.

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• Hovanes had to stop the meeting without going through the rest of the agenda since there was another meeting he had to attend.

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• Next meeting will be on 3rd of October.

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