Meeting 14 February 2024

Minutes from 2/14/2024 ePIC EEEmcal Readout Mtg

Schedule and SiPM orders:

• Most of this is already mentioned above or is now superceded by that--at the meeting we decided if we were going to test the 3mm models, we should do it with 20-siPM's per board to get the increased light collection area compared to the four 6mm's.
• Justin (now Gerard mostly) is in contact with Miguel about details of joining in on the irradiation plans at UC [Davis?] .

Requirements lIst/document:

• People mostly agreed with what I have in the document now with a few minor corrections.
• Sasha reiterated the need for the ~5 MeV threshold.
• The single tower dynamic range upper limit was more like 18 GeV rather than the 15 GeV i had estimated.
• Although we did discuss some aspects of needed number of bits for ADC (for example : the current dynamic range could be digitized safely with a 14 bit ADC in an old fashioned single ADC-per-pulse whereas with whole waveform sampling with multiple ADC samples Gerard agreed the effective precision in that scheme would likely be even much better than 14-bit) , Gerard reminded us that we shouldn't focus too much on ADC's nor include that in the requirements document, since it may not be applicable to the HGCROC approach.
• According to Sasha, the 1%/E term in the E resolution [from Tanja's summer 2023 specifications webpage linked in my slides] would usually be for accounting for various types of noise, but it seems that 1% there may be too bad if we want to do certain low energy measurements with the calorimeter. Coming back to this later in the meeting, Gerard said that there was a general epic-wide design goal to not let electronics noise contribute more than 10% of the noise budget [e.g. in quadrature, like for a resolution of 1% from other limitations, noise should not contribute more than 0.5% total ( since sqrt(1^2+ < 0.5^2 <= 1.1% ).]
• Concerning rate capabilities which are driven by the background, Gerard suggested we should try to get simulations of not just the rates at threshold, but the entire spectrum of the background hits at various detector radii .

Testing of siPM's - What to test?:

• As proposed on the slides going into the meeting, we will primiarly do bench testing of the siPM's first with only LED's illuminating the siPM's directly, doing similar analysis as shown by Gerard on Feb 7th in the calo meeting. This is primarily observing the noise level near and above threshold, timing resolution etc. For PDE, just measuring the response as a function of overvoltage should be sufficient. Doing these tests on non-irradiated siPM's, is mostly to just confirm the Hamamatsu specs, and establish a baseline for doing the same tests on the same testbenches on the irradiated siPM's. Also same tests as a function of ambient or board thermistor temperature should be done.

• Other tests should be done with crystals attached which will probably include cosmics testing [and per our subsequent discussion we also think radioactive source tests which could be done easily at Ohio U] to include realistic light yield testing.

• Gerard thinks the irradiation effects won't be much different for 6mm vs 3mm sizes, only may be different for 10 micron vs 15 micron pixel sizes.

Testing of siPM's/readout - Who ?:

• Gerard will focus on testing for the ADC's/FEB's and maybe some further testing of the 6015 model that will be used for the fwdEcal but the context of that detectors requirements.

• Therefore Lehigh/Ohio U/ACU will perform the bench tests for siPM decision making, Justin/Ohio U may try to get something set up on a slightly faster timescale, Lehigh and ACU may only be able to bulk of their testing starting in ~May, when they will have more summer person-power.

Lightguides

• Gerard also again brought up that we should look into the possibility of light guides for the 6mm^2 case, This would have a few steps involved, first designing what light guide geometry could be allowed, then producing some (probably machining ourselves out of plastic), attaching crystal/siPM adapter boards, include with full crystal tests. Since this is on a slightly longer timescale, we tabled this discussion for now. But it could probably be included with the full crystal tests after the irradiations are done.

Additional comments from Justin (email 2/22/24)

• Note also that a few developments have happened since last week that have updated some of what we were discussing at the meeting about schedule--a smaller group of us, including Gerard,Rosi, Larry, and myself have been having an email thread on this n the past week: Rosi's full order of ~100 3mm/15 micron pixel "3015" sIPM's have arrived already, and Larry has already done the very near-to-finalized design of the new 20-SiPM adapter boards for mounting the 3mmx3mm siPM's -- and he and Gerard are also finalizing the preamp "co-board". So we have all the design ingredients + siPM's needed for making and testing on the real prototype boards.. for the 3mm siPM's and possibly also for the 6mm siPM's. So we should proceed to getting prototypes of these boards fabricated ASAP and the siPM's mounted on them--Larry is confident now that he can do the siPM mounting for either size siPM. So we are hoping to get whole boards prepared in time for irradiating some entire boards with Miguel's irradiation tests in April. I'm suggesting we focus our priority on the 3015's at first, but about the (6mm)^2 since the four-siPM-601X boards were already also ready by Larry and Gerard, if we could get some 6015's siPM's from Tanja (since the ones ordered by me are likely delayed) we could also get to the same point for the 6015's.

• We may need to find some funds depending on the costs of the board fabrications, I think currently we are probably going to wait till the last tweaks of the board designs are finished and Larry will get some quotes.

• Additionally over the past week, thanks to Rosi's driving this discussion too, we have also fleshed out a little more on what tests with the siPM's/boards we will do and what the equipment/supply needs are for that. We expect that we will set up test benches at Lehigh, Ohio U, and I think Larry was thinking to set one up also in summer at ACU. This is a actually all pretty similar to what we had planned in the NSF proposal [but we'll be doing it with ~no/very small budget comparitively]. Some of the tests are described below in the minutes.