Optics Meeting Apr 24 2024 1100AM ET

Back to Main Page >> Optics Meetings

>> following meeting

>> previous meeting

Agenda

1. Kate - initial field study results and next steps [1] [2]
2. Bill - Database, GEM HV test data [3]

Attendance

1. Kate, David, Sayak, Tyler, Juliette, Bill, Vassu, Zuhal, Paul S.

Minutes

1. (Kate) Magnetic field study (see slides above). Have generated needed CSV files; checked various things, i.e. simulations were with correct 12C foil locations, sieve rotations worked correctly, B fields seemed to do what is expected (puzzle with the case of one field configuration, DipolePoint5Rand - will recheck that simulation was correctly generated, but don't need this one initially to make progress). Generated 1M events for each: pass2 3 different 12C foils, pass3 with one 12C and pass5 for Moller electrons. Looks like 1M events too small, will add additional 2M in each configuration. Plan is to write the fitting/diagnostic scripts in python, so can analyze the CSV files that way, perhaps in Jupyter notebooks for ease of students or others. Will attempt to fit the sieve hole images to ellipses, to get centroid in r, phi, rotation angle of ellipse in the r,phi plane, width along the major and minor axes of the ellipse. Discussion of possible ways to do the ellipse fitting; one option might be to output the contours when Root (or python) does a 2D contour plot.
2. (Vassu) Has written a .C script (generating_csv_files_v1.C) to do an automated determination of the events that belong to given sieve holes. Can be done with or without an energy cut to eliminate radiative tail (present tight radiative tail cut rejects events where E_beam - E_GEM_plane > 2 MeV). Routine divides each sector into three phi slices, does projection to radial axes, then does simple Gaussian fits, and determines a rectangular box in r, phi; all of the events in each box will have come from a single sieve hole. Test for 3 foils at each of pass 1,2 & 3 for nominal magnetic field. Works well. Produces diagnostic plots of the 2D hole images and the extracted box windows - can quickly check this plot by eye to see if the holes are all correctly found.
3. (Tyler) Working on adjusting his C++/root fitting class to somehow deal with cross-section weighting. Problem is that the Root function does not seem to have an option for applying weights to events, but are events are not cross-section weighted. Could one modify the 12C generators in remoll to throw with cross-section weighting. After discussion, it is suggested that (since the cross sections for all events from a given hole are probably very similar), could simply randomly sample from the generated events to select events to use in the fitting routine, with sampling based on relative cross section. That seems the simplest solution. Need to check that cross sections are essentially constant over events in a given hole (should be, since they represent a small range in theta_target).
4. (Bill) Update on MYSQL for GEM testing results. Actually the 10 leakage current values represent 20 HV sectors (pairs of HV sectors are wired to sum to one measured leakage current). Foils should be labelled by Batch # and Foil index. The comparison of the plots for given foil sector before and after the foil is mounted to a give frame may be a useful QA diagnostic.

Meeting link information

See email invitation, or contact David Armstrong, Kate Evans, or Jennifer McAllister for Zoom link