Minutes POLAR-2 Bi-Weekly meeting December 16th 2019

Attendance:

Geneva: Nicolas P, Nicolas dA, Merlin

NCBJ: Dominik

IHEP: Jianchao, Hancheng

MPE: J. Michael, (Jochen for post meeting)

Merlin: Update Geneva on scintillator simulations:

- Updated the POLAR-2 simulations software + first data analysis programs, will be placed on Github this week

-  Performed simulations of the signal + background using POLAR-2 and POLAR software to optimize scintillator length

- Optimum length found now is short: 75 mm, however, the minimum was not found yet (only went down to 75 mm)

- Needs some double checked, especially if changing the background incoming distributions have a large effect on this

- Taking M100 into account (or "figure of merit" as suggested by Jianchao) will likely push for shorter bars as well

- Nicolas: we should find the minimum first, if it is clearly very short we should go down to ~100 mm

- Merlin will continue the studies this week also checking for further off-axis angles

Nicolas dA: Update on SiPMs + scintillator design

- Preforming calibration of the SiPMs (from MPE) to find the IV curve at different temperatures

- Tested almost all, curves look good and values correspond to those given by Hamamatsu

- Went from -40 to +40 C, all SiPMs behave well

- Produit: we see from these plots that power supply for the SiPMs should be able to give ~1 mA (a few microA per channel).

- Figured we can use fully rectangular bars, requires optimization of the plastic grid

- First design done, will be send to cern in the coming days for production

- CERN can print things with a thickness below 100 micron, so with the current design we can use rectangular bars with a thickness of 5.9 mm (significantly better than the 5.4 used in POLAR)

Dominik: Update from Poland

- Was busy over the last weeks, will now work on the TDR, is using the template from svn

- For irradiation tests we have to discus with the group at NCBJ, they will have heavy ion tests in first half of next year, not sure about protons

- Merlin will send an email to start planning

- Produit + Dominik: need to produce some simple firmware specifically for irradiation tests of the GOWIN FPGA, will check in the coming weeks

J. Michael:

- Did not have time to look into the requirements for the Wok, will check in the coming days

- Jcohen did find some old BGO from GBM which can be used to play with

Jianchao:

- Will finish a funding application from IHEP on wednesday to apply for spectrometer production + data centre at IHEP

- Merlin clarifies that it is not planned to have the main data centre at IHEP, ideally data comes from CSU directly to Europe

- Jianchao clarifies that money for some computing facilities is needed anyway, no matter if IHEP takes the data directly from CSU or gets it from Europe.

- No official news yet about funding application with Yoni Granot, but quite clear they will receive the money for POLAR analayis, POLAR-2 studies + eXTP

(connection with Jianchao broke)

Post meeting Jochen + Merlin:

- Some money now exists to build some prototypes of the scintillators

- Ideally Jochen buys crystals with some SiPMs already mounted, Merlin will check for a BabyMIND board which we can lend to MPE

- Plan would that Merlin + Nicolas dA come for a week to help startup the readout of the crystal to check if the FEE of the polarimeter is suitable for spectrometer