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 ν detectors?
SEM courtesy F. Sauli
(*) © J. Learned
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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 ν detectors?
SEM courtesy F. Sauli
(*) © J. Learned
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(P.S. Barbeau NIM A 515(2003)439)
3M and CERN GEMs show comparable performance
Preliminary characterization
resolution
leakage current &
gain uniformity
gas gain
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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 GEM
3M GEM
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| 3M GEM | CERN GEM |
Ileak | 0.02nA/cm2 @ 600V in air at 40% R.H. | 0.005nA/cm2 @ 500V in N2 |
Gain ~1,000 @ 500V Ar/CO2 7:3 |
|
|
ElectronTransparency Ion Transparency | 0.9 0.9 | 0.9 0.6 |
Ion Feedback | 0.1 at G=20 Edrift=150V/cm | 0.08 Edrift=150V/cm |
Ageing | Ongoing (no signs of aging after 1 month) | 25 mC/mm2 Triple GEM @ Purdue 2000 |
Summary Comparison CERN and 3M GEM
(indeed very similar)
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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 LN2
5. Building calibration sources for ν application
(also exploring other detector technologies)
Further work on 3M GEM
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Feedback on first production all very positive:
• Heidelberg: no need to “train” GEMs, also easier 10B 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
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• 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
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