CSR LDRD March 19 2015

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David Douglas, Alicia Hofler, Yves Roblin, Chris Tennant.


  1. Status update
    1. Longitudinal match and parametric scans (Chris)
Chris presented the results of his studies regarding the longitudinal match from the injector to ARC1. See attached file for slides media:LDRD-03-18-2015.pdf
Litrack was used to calculate the longitudinal profile. the starting parameters were for a typical injector configuration with a 300fs bunchlength 
at the entrance of the chicane. Alicia has other simulations she did for various bunch charge and and bunchlength configurations. We want to explore 
transporting a longer bunch through the linac. 
It is unlikely one can see the microbunching in the longitudinal phase space with the CEBAF beam, however 
there is convincing evidence that one should be able to see the effect on the transverse phase space. An emittance growth of a factor of several is 
detectable for charges as low as 10 to 20 pc when switching from "bad" ARC optics(those that enhances CSR) to "good" ARC optics.
Yves will investigate whether one can setup a transverse tomography station on the 2nd step of the spreader and
at the recombiner at the end of the arc. Chris mentioned that he needs to incorporate the effect of the spreader on the dynamics of the beam to get a better
idea of the possibilities.  We will explore what the limits are in the linac in terms of bunch length (how low and how high we can go). 
    1. LDRD budget refactoring (Yves)
We presented the new plan early march at the CASA meeting. The slides are attached. Basically, one will refactor the LDRD to allow for money to be spend to buy 
a 96 CPU computer to run extensive GPT simulations for exploring the injector parameters.

List of tasks

  1. Yves:
    1. Produce spreader/arc match for the “good” and “bad” ARC.
    2. Check with Rui about Cheng Ying availability to calculate microbunching gain
    3. Investigate ability to do transverse tomography in spreader 2nd step and recombiner 2nd step.
  2. Chris:
    1. Send the lattices, see whether or not they match the actual ARC1 layout
    2. Extend the parameter scan to higher emittances, incorporate spreader
  3. Alicia:
    1. Review the injector simulations, maybe produce longitudinal dt/dp with more points
    2. Transverse phase space parameters for the simulation, which charge was it ?
    3. What is the max charge we can produce with existing setup (laser, etc..) regardless of transport
    4. Send higher charge per bunch simulations of injector to Chris (transverse em., bunchlength,bunch charge, e spread after ¼)
  4. Geoff:
    1. Ability of linac to transport short bunch with high charge. What are the limits on either side (short or long)?
  5. David
    1. Unearth documents about nuclear physics bypass.