CPS meeting - March 11, 2022

Agenda

• Announcements
• Introduction (Hovanes)
• Simulation updates (Vitaly)
• Discussions and other business

Minutes

Present: Hovanes, Vitaly, Moskov, Igor, Sean, Tim

• Hovanes announced that these meetings will occur every two weeks to deal with CPS technical design for Hall D. These are not replacements for CPS general monthly collaboration meeting organized by Tanya, but an addition to them. Significant results from these Hall D meetings will be presented at the general monthly meeting.

• Introduction (Hovanes)

• Hovanes presented the near term plan for CPS adaption.
• The highest priority was to confirm that the Hall C design could be adopted without changing the design of the magnet.
• The possible changes are increase of the beam-hole in x and y.
• Hovanes reminded that according to Todd the best choice for Hall D KLF for transversely spreading the beam intensity is to use a wide beam rather than a relatively narrower beam with some rastering. This would make beam setup easier and more stable. Eugene pointed out that the edges in Hall C would be sharper than for Gaussian model, so care must be taken.
• Eugene emphasized that all these assumptions about doubling the RMSs to compensate for the doubling of the power need to be proven with simulations. Eugene also pointed out that the RMS may not be a good indicator of what the maximum temperature is going to be in the copper core and copper radiator.
• See Hovanes' presentation for more details.

• FLUKA simulations (Vitaly)

• Vitaly ran FLUKA to determine the energy deposition in the CPS copper core with 12 GeV beam and narrow beam sizes (FWHM=0.45mm for x and y and FWHM=0.05mm for x and y). He is using Gaussian shape in both x- and y- for the electron beam intensity.
• The electron beam must have been deflected upward in the simulations, so the sign of the field may need to checked. It is easy to do, according to Vitaly.
• The peak of the energy deposition is at around z=+5cm. This is close what Hall C simulation were producing with 60cm magnet.
• The main discussion today was around the large vertical beam deflection is the vertical direction which amounted to 2.5mm at the location of the beryllium target.
• Vitaly identify that this deflection was due to the magnet field through which the electrons go before hitting the radiator. He fired the electrons just before the radiator to avoid the magnetic field before the radiator, and the vertical deflection was gone.
• It was suggested to pull the radiator back juts before the yoke (z=-41cm) for the next simulation and see if there is still any significant deflection. If there is still a deflection it might be dealt with a magnet, a new one or the existing 5C11B correcting magnets.
• Hovanes asked if the multiple scattering was enabled in the FLUKA simulations since it should define the photon beam size at the beryllium target. Vitaly thinks that it is enabled.
• Moskov argued that the fact that there is an non-zero angle between the photon beam and the z-axis can be beneficial for the K_long flux going from the beryllium target to the hydrogen target. But he would need to do some calculations or simulations to quantify that. Potentially this angle could be accommodated if it is not too large.

Action items

• Check for a new model from Gaby (Hovanes).
• Check the sign of the magnetic field.
• FLUKA simulation with radiator at z=-41cm. (Vitaly)
• FLUKA simulations with FWHM=0.52mm t determine energy deposition profile in the center of CPS. (Vitaly)
• Check the value of the photon beam angle needed with respect to z-axis to improve the Kaon flux at the LH2 target. (Moskov)
• Determine a good lattice for energy power deposition map for CPS simulations in FLUKA.

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