General Meeting Summary 9/20/17

PWO CRYSTAL CHARACTERIZATION - 160p FROM SICCAS

Discussion of results from visual inspection and dimension measurements of ten crystals from one (box #3) of the sixteen boxes

Overall crystal quality is not very good - visible defects, which seem to be due to manufacturing
Current dimension measurements are done with calipers
Another, perhaps better option for dimension measurements could be with optical methods

Several options are being explored, e.g. 1D laser micrometer
Instrumentation may also be available at JLab, but may be in a fixed location different from where crystals are stored

List of options for optical measurements and supplies needed, also check out instrumentation available at JLab
Send box#3 to CUA
Start visual inspection of additional boxes and record results

PWO REFLECTOR OPTIMIZATION

Geant4 simulation including crystal, reflector, and readout. Crystal modules are completely surrounded by reflector material, refractive index components (real and imaginary) of the materials are either available in simulation or have been implemented. Probe used for these is 50 MeV electrons. Optical contact is defined as distance order micrometer.
Air gap between crystal surface and reflector is important
Removing the air gap (few tens of micrometer) between crystal surface and reflector decreases the signal. Least sensitive is silver - need to check implementation of material properties of silver reflector

Note that simulation includes reflections from metallic surfaces in air but not dielectric - results should be interpreted qualitatively

Replacing the air gap with mylar between crystal surface and reflector recovers most of the signal. This may be checked experimentally
If front face left open (geometry during curing), signal reduced by 20-25%
Action items:

DIRC

DVCS ANALYSIS

NEXT MEETING: WED 27 SEPTEMBER at 10:00AM (EDT)

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