2016-Sep-16 Comp. Phys. Biweekly Report

He Zhang

• LEM upgrade: Investigating various scenarios to produce an efficient algorithm for optimizing the cryogenic load in the CEBAF linacs. From a given distribution, turning off zones and recalculating the cryo load. Less than a minute for a fully optimized solution when turning off as much as two zones (16 cavities).
• IMP data analysis: IMP data analysis: Write a new python script, which finds the Gaussian pulse more accurately and ignores the long tail on the edges, so that the rms bunch length plot suffers less from the random error. Also applied the bi-Gaussian fitting based on the new pulses with short tails, but no obvious improvement comparing with the results for pulses with long tails. This is probably reasonable, because the random error on edges is not necessarily change the fitting result. I need to think about more carefully on this issue.
• Cooling simulation: (1) The introduction to use the new electron cooling code is finished, which can be found here: https://github.com/zhanghe9704/electroncooling/blob/master/Readme.pdf. It explains how to define the collider ring, the ion beam, the electron beam, and the cooler; how to choose the formula for IBS and electron cooling effects, how to calculate the IBS and electron cooling rate, and how to perform tracking study for a period of time. The last section “advanced topics” is still empty, where I will add some details of the code usage. But what has been finished is good enough for basic use. (2) A five-page paper for the Advanced Accelerator Concept workshop is also finished and submitted. (3) Rui investigated the binary collision algorithm and helped me to understand it. Originally I thought an analytical formula can be used for two body collision. Turns out it is also need to be numerically solved. I think I will start tracking without the binary collision included. Then add it up to check the difference. (4) I am finishing and debugging the tracking code.

Yves Roblin

• Preparing optics for the new fall run - adjusted the 5 pass extraction optics to take into account the new 750 Mhz cavities. Turns out, we can't get a perfect extraction because of that. probably good enough.
  - investigating the proper relationship between Fourier decomposition of By(r,theta) fields in TOSCA and the formulation in terms of powers of X in MAD-X and ELEGANT. Derived the analytical feed down formulas, wrote a spreadsheet to demonstrate and validate. Integrating into the modeling of the CEBAF magnets.
  - attending various meetings on beam-beam, parameter configurations and tutorial talk preparation.
  - Preparing talk for collaboration mtg (Will need (1-2?) slides from Todd, Balsa, Mike, Wei)