CPS meeting - April 8, 2022
Agenda
- Announcements
- Minutes from previous meetings
- Simulation updates (Vitaly)
- Comparison to Hall C (Hovanes)
- Magnet field (Hovanes)
- Other items
Minutes
Present: Hovanes, Igor, Eugene, Vitaly, Sean, Tim, Pavel, Justin
Items from previous meetings
- Tim reported that since the tagger dump is rated just over 60KW, then we would be able to modify the water skit connections in the tagger to cool down the copper core of CPS.
- Hovanes compared the plot for energy deposition profiler along the z-axis for FWHM=1.2mm that was done by Vitaly for the last meeting to the one from one of the last Hall C CPS meetings. The energy deposition peak for Hall D is higher by a factor 1.6 and was slightly deeper in Z. The extra height of the peak might be due to the fact that the beam current n Hall D is 2x higher. The depth is probably due to the fact that Vitaly has a magnet in front of the CPS to compensate the beam deflection before the radiator.
- Bogdan commented that having the Hall C design "copied" into Hall D for KLF is inefficient and that Hall D would be better off designing a new magnet and corresponding shielding that may save costs.
Simulation updates (Vitaly)
- Vitaly made simulations using FLUKA for CPS with Gaussian beam with FWHM=2.5mm in x and y while increasing the beam hole to 5mmx5mm. He had to further increase the beam hole in front of the radiator to 1cmx1cm to avoid the hot spot and the beginning of the CPS. The wider entrance beam-hole improved the radiation dose by factor of ~100. The power deposition density decreased compared to FWHM=1.2mm. Vitaly estimated the radiation doses in the hall.
- Vitaly also tried replacing the volume field with tungsten with lead. He estimates that the radiation dose at the entrance of the CPS will be about twice higher with lead than with tungsten. He also had estimates for activation doses after one week and after one month for the two shielding configurations.
- We need to have some specifications for radiation levels in the tagger Hall. Pavel said he will work on that, currently he does not have numbers. But the numbers and restrictions will also depend on what equipment is expected to stay in the tagger hall and what work is expected to be done in the tagger during the experiment.
- Vitaly thinks that we need to determine the building blocks for the shielding and then build a more detailed FLUKA model and do the calculations. Bogdan was not convinced that this is the right way to go, at least not for this stage. Bogdan reiterated that a better way for Hall D is to conceptually design a new magnet and new shielding.
- Eugene commented that at this stage the most important issue is the heat deposition and the temperature distribution in the copper core. Once the magnet and the core configuration are selected, the shielding can be optimized.
- Eugene was worried about lead melting for the shielding configuration where tungsten is replaced by lead. Bogdan does not think it is a problem since the copper core is cooled by water that has to be under 100 degrees Celsius. Bogdan was pretty confident that cooling of the core with water speed of less than 3m/s will not a problem.
- Eugene inquired about copper core structure which is going to be under stress because of the heat and nonuniformity. Bogdan said that Hall C design has thin empty slots every 5mm to avoid potentials stresses and deformations of the copper core.
- Hovanes asked Vitaly to provide him with the binary files from the tungsten model calculations with FWHM=2.5mm . He will contact Vitaly later.
Magnetic field recalculations
- Hovanes took the OPERA model file from Bogdan that was used for Hall C 60cm magnet field calculations.
- He run OPERA at one of the JLAB computers and created three magnetic field files: one with the original grid, the other with the same steps sizes but with longer z-range, and one with finer y and z steps and longer z-range. All of them were for the original Bogdan's design. He saw discrepancy of less than 2% in the center of the magnet, which is probably not significant.
- Hovanes also learned enough about using OPERA so that he can modify Bogdan's magnet design and calculate fields within few days.
Action items
- Check for a new model from Gabriel. (Hovanes)
- FLUKA input and output file with beam FWHM=2.5mm to Hovanes. (Vitaly)
- FLUKA simulations with the new magnetic field maps (Vitaly)
- Check the value of the photon beam angle with respect to z-axis needed 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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