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Compton polarimetry meeting
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Description
Zoom Meeting link:
https://uvic.zoom.us/j/89000780435?pwd=HWqsdvSmD3aPlC4mZP10NCAuBkurJr.1
Chiral Belle Compton Polarimetry Meeting
2026 April 30
Savino Longo, Paolo Leo, Aurelien Martens, Nathan Kozak, Mike Roney
Next meeting: 8amVictoria/10am Winnipeg/5pm Paris 2 June 2026
Zoom Meeting: https://uvic.zoom.us/j/81687458300?pwd=E4FJ2HwaQebJPQnfULDHFfR2z7vAhA.1
Aurelien
Photon detector and Laser R&D Status
Nathan Kozak (starting grad student) working on simulation of system: light yields, PMT time-responses, BaF scintillation signal (including spectral components), work on experimental area , start work on local Co source, work with postdoc on GEANT4 description of system
Final design of DAQ and analog part of calorimeter will have full prototype in mid-2027
Do rad tests on calorimeter/PMT/DAQ at Orsay in beginning of 2028
(Chemistry lab with strong Cobalt source or use nuclear physics facility ALTO intense electron beam)
Main concern is that dose of signal is large
Barium Fluoride with 2 scintillation components (slow and fast with different wavelengths)
Keep UV (225nm peaking) fast component (0.3-0.6ns) to get bunch-by-bunch;
(Slow components ~600s ns, broad wavelength ~200nm lower limit – peaking at ~400nm)
UV Filter has a window of 20nm centred at 190-200nm
Need to test UV filter, which is not designed to be radiation-hard
Currently procuring from 2 Chinese companies (EPIC Crystals and Synopics) the BaF crystals
(cylindrical 15cm long, 1” diameter)
-
Depending on prototype performance –
Changing laser power to reduce event rate (and hence radiation) or pulse rate
Ultimate place the system near the location at SuperKEKB to understand the radiation background where the Compton polarimeter will be placed.
Not much update on laser development
- Looking at laser polarization measurements: issues of reliability
- Once we have formal approval of project, can get funds from INR
to procure all the hardware and test/validate
- Takes 1 year to procure the laser and assemble over 6 months.
Can also look at other European or Japanese sources
Savino
Electron detector R&D Status
Has one undergrad MITEC student working on Bmad simulations to track electrons
Second undergrad MITEC student working on GEANT simulation of beam pipe and magnet for scattering
They will start to work on this in June
Other questions:
Savino: What data is to be stored? Energy and time? Mentions coincidence with electron and photon signals has helped reduce backgrounds at Jefferson Lab.
Aurelien: initially considered only storing histograms, but can reexamine this. There is a 4GB link, which should be enough for storing event-by-event information.
Status of work on determining Location of Compton Polarimeter
- No updates from Aurelien
- Savino has 2 students lined up to work on this starting in June
Paris MOU draft: need the Appendix. Aurlien working on it with Ketel TURZO at CNRS
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