1. 1 Original motivation for first mass-production of MPGDs: Low-background applications (in particular coherent neutrino-nucleus scattering) “Wallpaper” photodetectors? (*) but many other applications can profit from “industrialization”: TPC readout, large-area tracking devices, X- ray astronomy, neutron physics, medical & industrial imaging, photonics... very large detectors? SEM courtesy F. Sauli (*) © J. Learned

2. 2 Original motivation for first mass-production of MPGDs: Low-background applications (in particular coherent neutrino-nucleus scattering) “Wallpaper” photodetectors? (*) but many other applications can profit from “industrialization”: TPC readout, large-area tracking devices, X- ray astronomy, neutron physics, medical & industrial imaging, photonics... very large detectors? SEM courtesy F. Sauli (*) © J. Learned

3. 3 (P.S. Barbeau NIM A 515(2003)439) 3M and CERN GEMs show comparable performance Preliminary characterization resolution leakage current & gain uniformity gas gain

4. 4 1. Electron transparency (no GEM gain) 2. Ion transparency (no GEM gain) 3. Ion feedback (with GEM gain) 4. Charging (with intense beam) 5. Aging Presented at Imaging2003 Further work on 3M GEM Sauli/Kappler/Ropelewski IEEE NSSS 2002 CERN GEM3M GEM

5. 5 CERN GEM I leak 0.02nA/cm 2 @ 600V in air at 40% R.H. 0.005nA/cm 2 @ 500V in N 2 Gain ~1,000 @ 500V Ar/CO 2 7:3  E/E ~16%  G(x,y)/G(x,y)~9%  E/E ~18%  G(x,y)/G(x,y) ~20% ElectronTransparency Ion Transparency 0.9 0.6 Ion Feedback0.1 at G=20 E drift= 150V/cm 0.08 E drift= 150V/cm AgeingOngoing (no signs of aging after 1 month) 25 mC/mm 2 Triple GEM @ Purdue 2000 Summary Comparison CERN and 3M GEM (indeed very similar)

6. 6 1. Single Electron detection with quadruple GEM 2. Self-supporting (glueless) stackable PEEK holders 3. Simultaneous charge/electroluminescence (extra PMT gain allows operation at higher P or two-phase) 4. 3M GEMs withstand T-cycling down to LN 2 5. Building calibration sources for application (also exploring other detector technologies) Further work on 3M GEM

7. 7 Feedback on first production all very positive: Heidelberg: no need to “train” GEMs, also easier 10 B coating due to absence of Kapton extrusions.Nice HV stability. Coimbra: very few defects using CCD method (originally developed precisely for inspection of mass-productions) NASA/LHEA, Harvard-Smithsonian, Novosibirsk, U. Michigan, BNL… Further work on 3M GEM: elsewhere distributed to ~15 groups so far CASCADE (Heidelberg) Coimbra

8. 8

9. 9 New source of MPGDs, extremely large productions possible. Cost of material itself essentially negligible. Opens door to widespread use of MPGDs in commercial and large detector applications. The solution to PMT cost issue for gigatonne detectors? Photocathode (PC) coating of MPGDs for photon detection demonstrated by a number of groups. However, something simpler to handle than inorganic PCs needed for mass- production -> ongoing research on organic PCs looks promising. Some R&D in order (but 3M already has the capability to add organic coatings as part of their process) Is the QE of bare metal sufficient? (Micromegas Ni mesh has been used as a PC previously) The possibility of producing even larger foils (~4 feet wide) using new dedicated machines seems possible (See M. Richmond’s presentation). Production of the large surfaces needed for gigatonne detectors feasible within a very reasonable time frame (few years) even with existing (16”) technology using dedicated machines (30 ft / minute!!!) …Must keep 3M enticed. It takes a very unique company to have the courage/will/time/interest to explore alternative markets. Conclusions