KLF beamline meeting - October 10, 2024

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Agenda

  • Announcements
  • Bleedthrough beam (Edith)
  • K-long rate calculations (Eugene)
  • Engineering update (Tim)
  • Any other business

Minutes

Present: Tim, Josh, Igor, Hovanes, Mikhail, Moskov, Eugene, Edy, Vitaly, Sashi, Lubomir, Justin, Marshall, Richard



  • Edith had a discussion with the BTeam of the accelerator division regarding the bleed-through beam during KLF.
  • The current expectation is that the bleed-through is going to be on the order of 1% from the "peak value". If the "peak value" is 5 μA (which is the averaged current for KLF), then the bleed-through current would be 50nA. They needed more information on what is the impact of the bleed-though for KLF. And BTeam would like to have some specification on what level of bleed-through KLF can tolerate.
  • Hovanes explained that the out-of-time bleed-through fills the time interval between the 64ns bunches that was deliberately created to allow us to measure the kaon momentum. All out of time bleed-through kaons will be interpreted as low momentum kaons thus causing potential problems for physics analysis at low kaon beam energies.
  • Moskov commented that Vitaly has done some analysis of Kn final state and studied the impact of a background channel on the yield at 0.1% bleed-through level. According to the preliminary results of this analysis, the background of 0.1% would not cause major problems.
  • Moskov also mentioned that having a 128ns beam bunching may allow us to measure the impact of the bleed-through.
  • There was a discussion about the priority and the schedule for measurements needed to evaluate the compatibility of KLF and MOLLER experiment. These measurements got delayed multiple time. Edy thought that there is no plan to do it during upcoming run, but Edy will check with the injector group about their plans. Hovanes pointed out that KLF needs to have the beam test results by this summer when we expect the next readiness review (ERR-2).



  • Mikhail presented the germanium detectors that the parasitic experiment is planning to install behind FCAL to take advantage of kaon beam during KLF.
  • There are five modules, each of them contain six crystals. They will need to be tested in Japan.
  • Each module requires LN2 cooling from the connection on the back of the module.
  • They think they will need to refill the nitrogen once per week if they have sufficiently large dewar.
  • One of the detector modules will be installed along the beam centered on the beam axis after the emulsion box. The other four will be somehow arranged to augment photon detection acceptance. The group also is considering placing a separate target in the beam.
  • There will be plastic scintillators for charged kaon detection. Vitaly asked how the kaon will be identified. Mikhail said that charged particles will be assumed as charged kaons. Vitaly also asked if a germanium detector package could be used as the target itself. Mikhail answer was that it could , but for a different experiment that does not require hydrogen or deuterium target.
  • Eugene asked about the size of the emulsion box. According to Mikhail, the emulsion box is 30x30x30cm. The whole hypernuclear station will be placed on an additional platform behind the FCAL platform. It will need to be movable.
  • Hovanes asked about the magnet for removal of the charged particles. Mikhail said that the only concern are slow protons. They plan to use a small permanent magnet to deflect these slow protons from the beam before they reach the emulsion box.
  • There was York University has some funding for this project (≲$50K). He suggested that they can design the germanium detector setup in UK and York also could pay a technician who will be at JLAB, possibly JLAB employee. Tim commented that JLAB engineers would have to be deeply involved in the design to make sure that the setup satisfy all the safety requirements.
  • Eugene asked for a sketch or drawing with all components of the hypernuclear station with their sizes on shown on it. It would be good if the estimated weights were shown as well. Mikhail will prepare such a sketch.



  • Richard was at the DNP conference in Boston , but he was able to connect to show his results from GEANT4 simulations of KLF.
  • First, Richard showed the comparison of the previous calculation with the empty target and SC with a cone with a new simulations with cylindrical SC of the same total length but full target. In both cases, Richard simulates 5B photons in the energy range of [2,12] GeV which corresponds to 1.2ms of KLF nominal beam time. Richard scales his phi photo-production cross section by a factor of 1000.
  • The hit rates in the start counter dropped by a factor of x10 in the cylindrical start counter with full target since the cylindrical SC does not have a nose cone and there are no interaction of the beam particles with the SC.
  • There was no noticeable change in the results for K-long, photon, and neutron rates at the target, as expected.
  • There was no much change for the hit rates in CDC, FDC, BCAL, FCAL, and TOF.
  • The Z-position distribution of the hits in the start counter changed. There was no downstream peak for a cylindrical start counter simulation.
  • The Z-position distribution of the hits in CDC did not change. There was still an enhancement at the upstream end. Eugene suggested to try to find the origin of the tracks creating the CDC hits. Richard has that information in the output files, but has not had time to study it.
  • The conclusion of the comparison of the cylindrical start counter and the existing start counter was that it only changes the hit rates in the start counter itself and does not affect the hit rates in the other detectors.
  • Richard also compared the hit rates in the nominal GlueX-II running with the hit rates in KLF. In both cases he used GEANT4. For GlueX-II, Richard used 50 micron diamond radiator, 350nA beam, 5mm collimator. He simulated 250M photons in the photon energy range of [0.0001,12] GeV which corresponds to 22ms of the nominal GlueX-II beam time. For KLF, Richard simulated the rates with variable tungsten plug thickness. The comparisons were done by normalizing both conditions to "per 64ns burst" counts.
  • Only 58M photons reached the LH2 target of GlueX-II , consistent with the collimation effect.
  • For the start counter, the W-plug thickness of 17cm will produce similar hit rates as for GlueX. If we use a cylindrical start counter without a cone, a 14cm plug would be sufficient to reach the GlueX-II start counter rates.
  • For CDC, even a 20cm thick tungsten does not reduce the hit rates to those simulated for GlueX. Some other avenues need to be studies for rate reduction in CDC. The CDC hits could be caused by particles travelling along the beam pipe that Pavel discussed during his previous presentations.
  • For FDC, a 14cm tungsten plug is sufficient to reach GlueX-II rates, based on the comparison of the rates averaged per FDC layer.
  • The BCAL rates in GlueX configuration are very low in GEANT4. They are not high for KLF conditions as well. Most likely BCAL rates will not be problem in KLF, according to Richard.
  • The FCAL rates become close to GlueX-II rates with a 17cm tungsten plug. But similar to BCAL, the FCAL rates in KLF are expected to be low anyway, so a 14cm tungsten plug probably would suffice as well.
  • A 14cm tungsten plug will reduce the TOF hit rates to the rates that GEANT4 gives for GlueX-II conditions, based on the average rate of the first TOF layer.
  • Richard conclusions were that a 14cm plug will reduce the detector hit rates to the level of GlueX-II, with the exception of CDC. In case of SC, the interactions in the nose cone would have to be significantly reduced, or completely removed by changing the start counter design, to match GlueX-II SC rates.
  • μ-conversions, high energy γn interactions, and high energy neutron physics still are not modeled well in Richard's program. This could explain the low rates simulated in BCAL compared to real rates seen in the experiment.
  • Lubomir asked if the 100 micron tungsten film in front of the GlueX collimator was included in the GlueX-II calculations. Richard said that for GlueX-II conditions he only used photons above 100keV in his comparison so that he did not have to worry about the tungsten film. Those low energy photons are not present in the simulated GlueX-II primary beam from the very beginning (lowers GlueX-II rates in the simulations).



  • We were already 10 minutes over the one hour mark, so Hovanes had to stop the meeting.



  • Our next meeting will be on the 17th of October.


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