Compton Meeting, August 13, 2013

1. Dial Toll-Free Number: 866-740-1260 (U.S. & Canada)
2. International participants dial:
Toll Number: 303-248-0285=
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 --> our access code is 3227471

Agenda

No meeting room. Call in, or come to Dave's office.

Miscellaneous

• Need to pick new meeting time
  • Doodle poll here.
• Amrendra will come to NN the week of August 26 to help with QWAD removal
• Need to schedule time to make laser table ready for beamline work.

Laser

Polarimetry plan:

As the final step in measuring the laser polarization and constraining the uncertainty we aim to measure or bound any loss of polarization occurring between the polarizing cube and the interaction point. Assuming that we have remote control of the elements on the table and the previous scan routines work.

This will be done with a Thorlabs polarimeter head. In order to gain confidence in this device, we will expect to see it duplicate the already extracted results for the polarized component.

1. Run the usual polarization mapping procedure (elements are already installed)
   1. Large scale, coarse steps (to determine the regions of maximum circular polarization and to compare to previous maps.)
   2. Smaller scale, fine steps (to precisely determine the position of maximum circular polarization.)
2. Remove elements used for standard mapping.
3. Install the Thorlabs polarimeter head in the interaction region and measure the stokes parameters, including degree of polarization at the maximum circular polarization of both signs. Spot check other polarizations to check against fit results. Further characterize polarimeter by measuring the power dependence, angle dependence etc.
4. Check measurement of DOP in-situ directly, by installing a GL polarizer immediately upstream (should get 100% linear, 100% DOP).
   1. Assuming all results make sense, we have measured or bounded the depolarization, we are done.
5. (Optional for if Thorlabs polarimeter untrustworthy) We may be able to make some clever measurements with a QWP and only 1 detector. Need to be smart to aviod this becoming a multi-day effort with a Babinet compensator.

Photon Detector

• Certifying the Monte Carlo
• Linearity plans - CH available.
• Data analysis?

Electron detector

• Comparison of "scaler" vs. "triggered" asymmetries and polarizations: scaler based results consistently smaller. See Edet log 542.
  • Example run: 22679 Edet log 545
  • Another example: 23476 Edet log 546
  • Simulation including noise and background Edet log 548
  • Comparing different regions of asymmetry spectrum Edet log 549
• Effect of noise on trigger Edet log 544
• Effect of strip efficiency on polarization Edet log 547