2017-Apr-16 Comp. Phys. Biweekly Report

He Zhang:

• Cooling simulation for bunched electron cooling simulation at IMP: First, I checked the simulations from IMP to make sure we use the same parameters. With the same parameters, the cooling time is much shorter than before, and thus much closer to the experiment. Second, I added an RF cavity element into our cooling simulation code, JSPECT. The users can define the RF voltage, harmonic number, initial phase, and the phase of the reference particle. Starting with a coasting ion beam, now we can simulate the bunching process. Depending on the height of the RF bucket, the momentum spread may increase during the bunching, then it decreases due to the cooling effect and as the same time the bunch length decreases too. I have run a few test simulations using the IMP parameters, and the result looks reasonable. I will do more test run, and do some simulations for the coming IMP experiments.
• JLEIC collaboration meeting: Prepared the slides and gave a presentation on electron cooling simulation in the JLEIC collaboration meeting.
• Paper for IPAC2017: Finished the draft for IPAC2017 paper. The paper is about the optimization of the RF cavity heat load and trip rate for CEBAF at 12 GeV. Following Balsa’s work, we implement GA on the system and find the pareto-optimal front. More important, we investigated how to find the new PF quickly, if some cavities turned off. We proposed three different ways to generate initial population for fast convergence: scaling up the gradients, scaling up the gradients with the guidance of the heat load derivative, and adding trip rate optimized individuals to the initial population. With the strategically generated initial population, the PF can be found in about 20 seconds for up to 15 cavities off.

Yves Roblin

• Continuing beam-beam comparisons btw GHOST and BB3D. Found a much better working point for the e- ring which alleviate most of the luminosity degradation.
• Worked on the upcoming isotope experiment, prepared optics and material for the readiness review.
• Reviewed IPAC paper on RF cavity optimization
• Reviewed LDRD proposal for extending GHOST with FMM method in order to go beyond the Bassetti-Erksine approx. The proposal is now submitted (No extra funding requested for B. Terzic since its already in the other contract)
• Presented talk at the JLEIC meeting, ran the session on simulations.
• Assisting Hall A physicists for the upcoming readiness review on PREX/CREX. In particular, exploring whether or not the effect of the fringe field of the non-superconducting Q1 quadrupole affects the size of the spot on the dump.
• Prototyping the new autosteer code. Essentially ready to be tested with beam this fall. Generated test cases, comparing with real archived data. Using the Raytrace data taken by M. Tiefenback to load into ELEGANT and fit for orbit+bpm gains+magnet errors similar to what I did a few years ago with the LOCO method)