Optics Meeting May 31 2022 230PM ET
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[hide]Agenda
Attendance
Kate, Bill, Vassu, David, Ciprian, Chandan, Brynna, Jim
Minutes
- Kate - has compared blocker "punch through" for Moller hydrogen target generator for three kinds of blocker (90 mm of pure W, 90 mm of Cu/W 10/90, and 110 mm of Cu/W 10/90, where the last one is approximately the same total radiation length as the 90 mm pure W) and compared to the rates with no blocker. For the rate of charged particles on ring 5 (key parameter for the blocker) we find around 0.1% (details in slides), but a preference for 110 mm thick rather than 90 mm thick for the 10/90 alloy that engineering will require us to use. Photon fractional are higher, but this is less relevant for the background measurement that the blocker is designed for. Note that we don't need to use the same thickness for the sieve collimator - likely could tolerate larger "punch through" fraction for the sieve.
- Vassu - question re: use of data from holes that are not fully contained in single GEM acceptance for default azimuthal rotation position? After some discussion, for now (as we develop the optics algorithm) we should assume "full" GEM acceptance across the azimuth, so we don't get confused. Once the algorithm is established, we can ensure that there is at least one GEM measurement position for which the entire data from each collimator hole is contained (the fitting algorithm can combine data from multiple runs to get multiple holes). Need to remember to ensure that Rotator will be able to stop at all the relevant angles.
- Vassu - used Moller generator from lH2, no sieve. Looked to see if the v_z dependence for the GEM coordinates (R,R',phi,phi') is more than just the theta_lab dependence (since for a given sieve hole, the radius of the hole and v_z determines theta from simple trig. Two different approaches seem to yield equivalent results that there is a non-trivial residual v_z dependence after the dominant theta dependence is removed. Rough scale is that for the same theta, there is a 1 ppm variation in asymmetry when v_z varies by one meter along the target. So, we would want/need to determine v_z (independent from theta) from optics data.
- Vassu/Kate - have some ideas of how to get v_z from optics data. Will review next meeting.
- All - trying to understand the cause of the residual v_z dependence. Consensus is that this may be the following: for a given incident beam particle energy, the asymmetry just depends on theta_cm (and therefore theta_lab) in a one-to-one manner. However, in a thick target, like our hydrogen target, the beam on averages loses energy due to dE/dx and bremsstrahlung events, the energy loss increases as one moves in z along the target and so for a given theta_lab, there may be different asymmetries depending on v_z, as the simulation indicates. Could check this in the simulation by looking at how the energy varies (for fixed theta) as v_z changes, or by simulating with a low-density target.
- Discussion of need to "tilt" the sieve holes (not done in present simulation) and how to determine the optimum sieve hole diameter, and whether simple hole-drilling vs. wire EDM might be needed. Still to determine both of these.
Meeting link information
Meeting URL
https://cwm.zoom.us/j/97259755403?pwd=WTRqVHJnZ3RQa1IwNHdMQjJuQm9FZz09
Meeting ID: 972 5975 5403
Passcode: 4937
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