Dear Roberto,
My apologies but I won't be able to make it to tomorrow's meeting; I will be available later in the day and will watch the recording.
We have only tuned the optics to a level that would permit us to develop the reconstruction algorithms, and have not yet spent time optimizing further. For reference, our envelope limits (at z=back of dRICH) span roughly 1.3 < eta < 3.7, so we should be able to do much better than what was shown at the collaboration meeting.
See figures for our last tuning attempt, way back in August 2022: https://github.com/eic/epic/pull/24
However! Today I just noticed the optics are once again messed up; see the updated attached figure. So we can absolutely do better than eta<2.3, since currently at high eta the reflected photons are missing the sensors. This degradation of the optics was likely caused by all the little last minute changes to geometry we had to make in preparation for the first campaign.
We have a few ways forward:
Move to dual mirror or multi-mirror configurations, to try to combat against the spherical aberrations. The aberration spreads out the focal region enough such that it's practically impossible to have both high and low eta in focus at the same time
Machine learning optimization; as far as I know the wheels are in motion for this from Cristiano's side, and our brute-force optimizer automation should work as an entry point
Also, our aerogel radius is not as large as we would want for ideal acceptance, so we don't get any aerogel rings at lowest eta (my slide/Chandra's figure showed gas acceptance only); unfortunately I don't think we can enlarge it without discussions with GD/I, but at least the DIRC geometrically covers this region pretty well.
Links for geometry views
2D, full ePIC: https://eic.github.io/epic/artifacts/epic_arches_views/view1_top.pdf
3D interactive: https://eic.github.io/epic/geoviewer?file=artifacts/tgeo/drich_only.root&item=default;1&opt=zoom200;ROTY290;ROTZ350;trz0;trr0;ctrl;all
Cheers,
Chris
