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“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
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“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
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Preliminary characterization
(P.S. Barbeau NIM A 515(2003)439)
resolution
leakage current &
gain uniformity
gas gain
3M and CERN GEMs show comparable performance
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Further work on 3M GEM
1. Electron transparency (no GEM gain) Presented at
2. Ion transparency (no GEM gain)
Imaging2003
3. Ion feedback (with GEM gain)
4. Charging (with intense beam)
5. Aging
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3M GEM
CERN GEM
E lec tron T ransparenc y
0.8
0.6
0.4
0.2
Ar:DME=9:1, Ed=50 V/cm, Et=2.5kV/cm
Ar:DME=9:1, Ed=150 V/cm, Et=2.5 kV/cm
Ar:DME=7:3, Ed=150 V/cm, Et=2.5 kV/cm
Ar=100%, Ed=150V/cm, Et=1.5kV/cm
DME=100%, Ed=150V/cm, Et=2.5 kV/cm
0
0
50
100
Vgem (V)
150
200
Sauli/Kappler/Ropelewski IEEE NSSS 2002
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Summary Comparison CERN and 3M GEM
(indeed very similar)
3M GEM
CERN GEM
0.02nA/cm2 @
600V in air at
40% R.H.
0.005nA/cm2 @
500V in N2
~1,000 @ 500V Ar/CO2 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
0.9
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
Ileak
Gain
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Further work on 3M 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. 3M GEMs withstand T-cycling down to LN2
5. Building calibration sources for n application
(also exploring other detector technologies)
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Further work on 3M GEM: elsewhere
distributed to ~15 groups so far
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…
Coimbra
CASCADE
(Heidelberg)
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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 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.
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