Wallpaper photodetectors Original motivation for first massproduction of

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

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

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

Further work on 3 M GEM 1. Electron transparency (no GEM gain) Presented at 2. Ion transparency (no GEM gain) Imaging 2003 3. Ion feedback (with GEM gain) 4. Charging (with intense beam) 5. Aging 3 M GEM CERN GEM Sauli/Kappler/Ropelewski IEEE NSSS 2002 4

Summary Comparison CERN and 3 M GEM (indeed very similar) 3 M GEM CERN GEM 0. 02 n. A/cm 2 @ 600 V in air at 40% R. H. 0. 005 n. A/cm 2 @ 500 V in N 2 ~1, 000 @ 500 V 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% Electron. Transparency Ion Transparency 0. 9 0. 6 Ion Feedback 0. 1 at G=20 Edrift=150 V/cm 0. 08 Edrift=150 V/cm Ageing Ongoing (no signs of aging after 1 month) 25 m. C/mm 2 Triple GEM @ Purdue 2000 Ileak Gain 5

Further work on 3 M GEM 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. 3 M GEMs withstand T-cycling down to LN 2 5. Building calibration sources for n application (also exploring other detector technologies) 6

Further work on 3 M GEM: elsewhere distributed to ~15 groups so far 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… Coimbra CASCADE (Heidelberg) 7

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Conclusions • 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 massproduction -> ongoing research on organic PCs looks promising. Some R&D in order (but 3 M 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 3 M enticed. It takes a very unique company to have the courage/will/time/interest to explore alternative markets. 9