KLF beamline meeting - October 17, 2024

Agenda

• Announcements

• Beam tests in 2025 and beam bleed-through (Riad, Edy)

1. MOLLER related Beam Tests: (Note: laser is back to 249.5 MHz, need to switch to low-rep laser (need one shift))
   1. Study photocathode effects from KLong beam
   2. Deliver Hall D Low-rep Rate and High Bunch Charge Beam to Hall
2. Hall D Bleed-through:
   1. RF bleed-through results from bad RF Separator phasing in Beam Switch Yard. This can be eliminated.
   2. Bleed-through that originates at injector because each drive laser produces some dc beam that bleeds across all three chopper slits. We measured bleed-through in injector using different lasers (Mode-Locked laser vs. Gain-Switched laser), but found the same level of bleed-through as our Gain-Switched based drive lasers. All Hall D empty RF buckets will be filled with bleed-through current from Hall D laser in addition to the bleed-through from the other lasers. Other halls worried about effect on polarization, otherwise no issues. KLong should worry about accidentals and timing. Accelerator wants a requirement document. Bleed-through can be measured in injector. We will need to submit a beam test request. KLong DAQ should also receive a 15.6 MHz timing signal from Injector.

• FLUKA simulations (Pavel)

• Updates from GEANT4 simulations (Richard)

• Hypernuclei station (Mikhail)

• Engineering update (Tim)

• Any other business

Minutes

Present: Vitaly, Beni, Tim, Josh, Hovanes, Igor, Riad, Pavel, Edy, Mikhail, Marshall, Sashi, Moskov

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• Riad discussed the plans for the beam tests during 2025 runs. He thinks he would need two "beam study days" to get reasonably conclusive results.
• Riad pointed out that these measurements were planned earlier but were not done due to a lower priority assigned to them. The priority of these tests is affected by the Physics Division input, and we would need to be a high priority item on the Physics Division list not be bumped off the schedule for the beam studies.
• Edy can help some of us be included in the meetings of the "BTeam".
• Riad expects that the bleed-through will be on the level of 1%. Hovanes asked why it should not stay at ~3nA as measured during KLF instead if the slit aperture is not changed. Beni commented that for KLF the DC beam-current will be the sum of the other halls, as for GlueX, plus leakage from KLF laser. Riad expects that Hall D laser for KLF may substantially change the DC-beam-current and increase the bleed-through. The dark current level of KLF laser can be measured at the injector.
• Injector group would like to have specs for bleed-through from KLF. This could be a slide describing the impact of the bleed-through and the maximum bleed-through current that could be tolerated by KLF. Moskov and Vitaly commented that they have estimated the impact of 0.1% bleed-though. At this time KLF does not have specifications for the out-of-time bleed-through current.

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