[Erd108] MPGD: The Path forward

[Kondo Gnanvo]

Dear Rolf, Elke, Silvia, John
Thanks for the summary of the Outer uRWELL tracker meeting and the very productive discussion on the option and path forward.
We had a follow up discussion on the matter at our eRD108 meeting.
We agree that the suggestion / recommendation to start a parallel E&D effort that focused on the "common" mechanical structure design for 3 prototypes (standard 3 mm gap, single amplification thin gap and hybrid amplification thin gap) is the best approach and would not result in additional  delay as it maintains the standard 3 mm gap uRWELL as a reference (i.e. backup solution) that would not require additional E&D.

To illustrate why we are confident that hybrid thin-gap is compatible with the mechanical support structure of  a standard gap uRWELL, I prepared a few slides witj the cartoon cross sectional views of the 3 detector options showing a breakdown of the different elements of the mechanical support.

You could see that with this design, when going from single amplification to hybrid amplification with GEM, the only additional elements are the GEM foil and the induction gap frame. But most importantly, the "cathode block" is used as support structure of the GEM during the assembly (stretching and gluing) and  is strong enough to sustain the tension of the stretched GEM foil (which is the only stretched foil).
The uRWELL-RO block which remain the same all 3 designs, will also help maintain further the tension of the stretched GEM foil in the hybrid thin gap case
In addition, we are thinking of some very simple and straightforward ideas (see backup slides) to reinforce the overall mechanical structure of the detectors at no additional R&D cost and delay.

If this slides help clarifies some of the concerns regarding the hybrid options and you are ok with the approach, then we are ready to start follow up meetings on specific mechanical support design.

Best regards
Kondo


From: Rolf Ent <ent at jlab.org>
Sent: Monday, October 2, 2023 10:38 AM
To: Aschenauer, Elke <elke at bnl.gov>; Brian Eng <beng at jlab.org>; Kondo Gnanvo <kagnanvo at jlab.org>; Francesco Bossu <francesco.bossu at cea.fr>; maxence.vandenbroucke <maxence.vandenbroucke at cea.fr>; Ernst Sichtermann <epsichtermann at lbl.gov>; Matthew Posik <posik at temple.edu>; Lajoie, John G [PHYSA] <lajoie at iastate.edu>; Silvia Dalla Torre <silvia.dallatorre at cern.ch>
Subject: Re: MPGD: The Path forward

Dear all,

attached a summary of the MPGD: Path Forward meeting that we had in last week's Thursday
tracking WG slot. It folds in comments by Elke, Silvia and me, and a question John had. There
are some action items. Hopefully we can soon have a follow-up as we have to get this in motion.

Thanks to all for the constructive (long) meeting last Thursday.

Best regards,  Rolf
________________________________
From: Aschenauer, Elke <elke at bnl.gov<mailto:elke at bnl.gov>>
Sent: Wednesday, September 20, 2023 5:38 AM
To: Brian Eng <beng at jlab.org<mailto:beng at jlab.org>>; Kondo Gnanvo <kagnanvo at jlab.org<mailto:kagnanvo at jlab.org>>; Francesco Bossu <francesco.bossu at cea.fr<mailto:francesco.bossu at cea.fr>>; maxence.vandenbroucke <maxence.vandenbroucke at cea.fr<mailto:maxence.vandenbroucke at cea.fr>>; Rolf Ent <ent at jlab.org<mailto:ent at jlab.org>>; Ernst Sichtermann <epsichtermann at lbl.gov<mailto:epsichtermann at lbl.gov>>; Matthew Posik <posik at temple.edu<mailto:posik at temple.edu>>; Lajoie, John G [PHYSA] <lajoie at iastate.edu<mailto:lajoie at iastate.edu>>; Silvia Dalla Torre <silvia.dallatorre at cern.ch<mailto:silvia.dallatorre at cern.ch>>; Aschenauer, Elke <elke at bnl.gov<mailto:elke at bnl.gov>>
Subject: [EXTERNAL] MPGD: The Path forward


Dear All,

As we discussed last Thursday we would like to meet again on Thursday 11:00 am 28th of September (assuming there is no tracking WG meeting scheduled at that time). To begin with, we would like to thank the presenters at last Monday's TIC meeting for the progress they have already made folding in the discussion from last Thursday's meeting.



Based on the excellent information we have received so far, we would like to define a path forward as preparation for our next meeting.  To that end we are circulating the following questions/discussion points. One base assumption that we will make is that heavy gases, i.e. Xe and Kr are available at the time EIC is operating. Based on this assumption we would like to understand:

1. What R&D needs still to be finalized to show that the Standard μRWell (as discussed on slide 5  of Kondo's TIC presentation, leftmost column) provides an option for an MPGD tracker for ePIC even if the hit resolution is inadequate. We would also like to see a time estimate needed to complete this R&D.

2. What additional R&D is needed to make a thin-gap μRWell (as discussed on slide 5 of Kondo's TIC presentation, 2nd column from the left) an option for an MPGD tracker for ePIC. We want also would like to see a time estimate needed to complete the R&D for a full-size thin-gap μRWell prototype. Again, we note that this should assume the availability of heavy noble gases and the gas should be chose to optimize the stability of the detector.



While the hybrid GEM/uRWell may have applications in future detectors, the additional R&D required is inconsistent with the project timeline and introduces too much risk.  The hybrid designs are not an option for ePIC.



In parallel to developing the requested information about remaining R&D, Matt Posik's simulation studies should be pursued because they will guide how small the μRWell gap needs to be, i.e., maybe can one live with a drift gap of 2mm instead of 1mm. It will be important to make the two methods of determining the angular resolution at the hpDIRC converge in the simulation studies so we can have some confidence in the results. The Astropix hits should also be included in these simulation studies, and any remaining issues in defining the MC "truth" hit position in the hpDIRC resolved.

With this parallel approach we believe the discussion boils down to a single parameter - the size of the drift gap in the μRWell.  The simulation studies will set this by determining the required spatial resolution, and an understanding of the remaining R&D and how that depends on the size of the drift gap will inform the plan to develop the outer MPGD for ePIC.

Thanks,

John, Silvia, Rolf and Elke




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