Collimator optimization
From Hall A Wiki
There are two stages to the collimator design. The first is to determine the optimal collimation for the moller acceptance for the default field map. The next is to eliminate one-bounce photons which may hit the primary detectors. Sereres (UMass grad student) will be taking on these projects, with supervision from Juliette and KK. Tackling the first one will allow her to become familiar with the simulation and farm interactions, as well as begin development of useful scripts. The second will be longer-term and involve much more careful consideration.
Line of sight
- Use CAD to eliminate line of site to the target from the detectors
Optimize Moller Acceptance
- Look at tracks
- determine z location of acceptance definition (low and high scattering angle acceptance as well as phi acceptance)
- determine ranges for the radii of the collimator edges (either with no other collimators or be careful of interference)
- for each collimator, choose a reasonable step size within which to change the radius
- Perform "studies" for each collimator to optimize the acceptance defined by each
- send multiple jobs for each step for each collimator to the farm (high statistics)
- chain and analyze multiple jobs
- produce plots of figure(s) of merit (Moller, elastic ep and inelastic ep rates, moller peak width, ep/moller separation, asymmetry, transverse asymmetry?) as a function of collimator position
- Choose a default collimator definition
- z-location of acceptance defining collimator - upstream of upstream torus or hybrid?
- trade-off between sensitivity to position/spot size and the acceptance depending on field
Eliminate (or minimize) 1-bounce photons
- Juliette's summer student looking at origin of photons which hit the detector plane
- Look at tracks (coarsely determine shielding locations)
- need clearance of tracks with coils
- collimators/sheilding needs to be integrated with coils/support structure
- collimators will be sources of photon background - choose z locations of shielding
- Studies to optimize the shielding
- reasonable steps in position
- plot FOM vs. step
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