Agenda

Minutes

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

Moskov announced that ODU group is interested in building a new start counter for KLF. It would be similar to GlueX start counter but it will a have wider opening (≥6cm) in the cone or will be cylindrical.
Eugene pointed out that making cylindrical start counter will take shorter time.

Pavel continued simulations with his FLUKA model of the collimator cave and the main hall. He does two kind of simulations: full simulation with low energy thresholds for particles; and high energy simulations where the momentum threshold is 500 MeV for all particles, but is 20 MeV for neutrons.

Pavel tried both 10cm and 14cm tungsten plugs. Photon spectra for both thicknesses look similar, but the rate is reduces by about factor of 20.

Kaon rate from FLUKA with a 14cm plug is 6.3 KHz, ~25% reduction with respect to 10cm plug. Neutron rate is about 40KHz.

Pavel summarized his findings regarding the background in the hall: low energy photons hitting the target; high energy forward particles penetrating through the concrete around the beamline in the cave labyrinth walls; diverging beam cascading in the beamline. He thinks a combination of thicker (14cm according to Richard's optimization) plug, heavier core around the beam pipe in the cave, and shielded beam pipe may solve the high rates in the detector.

Having a shielded beam pipe with respect to unshielded pipe with 14cm tungsten plug reduces the dose rates in the location of CDC by about a factor of ~7.

Pavel stated that with 14cm plug the main background inside the beampipe is from neutrons while at 10cm the largest background were the photons. The neutrons can be problem for FCAL.

Eugene suggested to have a beampipe with variable thickness, baffles, to reduce the background rate from cascading in the beampipe not only outside of the beampipe but also in the beam pipe.

Hovanes reminded us that the beam pipe between the target refrigerator and the target cell is pretty wide, about the same size as the start counter. the upstream flange of the refrigerator could be a good place to place a collimator. The pipe may contain target plumbing inside though. Pavel would like to have drawings.

Moskov asked if Pavel can make any conclusions about the need for a new start counter, beam pipe and tungsten plug thickness. Pavel thinks that his studies show the sources of the background and possible ways to shield them, but the optimization should be done using the actual detector rates which is what Richard is doing.