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

Note: Please do not feel obligated to respond to this message outside of your work hours.