- 1 - 01/12/2015 cbm micro pattern detectors and a first sketch of a high granularity muon chamber...
TRANSCRIPT
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/18/
23
CBM
Micro Pattern Detectors
and a First
Sketch of a High
Granularity Muon Chamber
for CBM
Christian J. Schmidt
GSI
CBM Muon Detection WorkshopGSI Darmstadt, October 16 to 18, 2006
- 2 - 18/04/23 CBM Muon Detection Workshop, GSI Darmstadt, October 16 – 18, 2006 CBM
Outline
History of micro pattern detectors
The GEM in particular
Sketch of a GEM-based Muon chamber
- 3 - 18/04/23 CBM Muon Detection Workshop, GSI Darmstadt, October 16 – 18, 2006 CBM
Micro-Pattern Gas Detectors: many similar concepts
MSGC by Anton Oed (first µ-detector concept originated in neutron physics)
GEM by Fabio Sauli
MICROMEGAS by Y. Giomataris and G. Charpak et al.
Micro-DOT by Biagi
µCAT (Compteur a trous) by Lemonnier
... Micro Wire, Micro-Pin Array (MIPA), Micro-Tube ... ... Micro-Well, Micro-Trench, Micro-Groove ...
most importantly: micro = fast due to short ion drift
Very creative phase in the ninties: seeking advances beyond the MWPCfor targeted HEP-experiments
Overview: F. Sauli and A. Sharma: Micropattern Gaseous Detectors, Ann. Rev. Nucl. Part. Sci. 49(1999)341
- 4 - 18/04/23 CBM Muon Detection Workshop, GSI Darmstadt, October 16 – 18, 2006 CBM
The Gas Electron Multiplier (GEM)
Amplifier Mode In hole high fields allow
Gas amplification 1 - 400
Transparent Mode At gain 1, electric fields
transport charges through the holes
ElectronsIons
pict
ures
from
Sau
li
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GEM- History since invention 1997 by F. Sauli
HERA-B: First HEP-Experiment to push from kHz to MHz event-rate First HEP-Experiment to employ MSGCs on large scale
- Detect minimaly ionizing particles (tracks) in inner tracker detector, depositing approx. 1 to 10 keV
- But get highly ionizing events up to 50000 times stronger also- rapid ageing- direct discharge damage to microstructures
- GEM was to introduce two step charge amplification,
leaving MSGC-amplification at a moderate gain of 50 to 300.
damage at MSGC
HERA-B inner tracker module,an MSGC-GEM combination
200 built at Heidelberg 50 my development effortby Eisele et al.
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GEM- History
Today, HEP have largely decided for Si-Strip-Detectors:
CMSLHCB
ALICE ...
GEMs not robust enough for signal spectrum with MIPs and HIPsSilicon strip detectors are industrially availability today (Hamamatsu)
HEP application left: TPC – at Linerar Colliders etc. (TESLA)
COMPASS @ CERN:Large scale employment of tripple GEM tracking detectors 31cm x 31cm (operative!)
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Other current and some exotic applications for GEMs Single photon detection employing mutiple, cascaded GEMs
Breskin et al., C. Richter (Diss.)
Gain and readout for TPCs in HEP (M. Killenberg et al.)
Coherent Neutrino Detection (J. Collar et al. 2003)
low background materials
sensitivity to sub keV recoil energies
feasibility of very high gain (~105) at very high pressure (20 atm)
Solid converter neutron detection (CASCADE-Detector)
Optical readout of scintillation after
neutron conversion through 3He
Fraga et al., G. Manzin (ILL)
GEM-preamp for Ultra Cold Neutron detection (Heidelberg)
X-Ray Polarimeter (E. Costa et al., R. Bellazini et al.)
- 8 - 18/04/23 CBM Muon Detection Workshop, GSI Darmstadt, October 16 – 18, 2006 CBM
Particular, unique properties of GEMs
allow multi-stage amplification
amplification decoupled from readout
avoid high gain photon positive feedback single photon detection with suppression of
ion- as well as photon-feedback
inherent high rates capability through micro scale
minimal magnetic distortion through micro scale
robust technology
“simple” lithographic production process industrially available production by CERN and in the future by Polish CERN licencee ... ???
3M has also developed a large scale production process for 12´´ x 12´´
- 9 - 18/04/23 CBM Muon Detection Workshop, GSI Darmstadt, October 16 – 18, 2006 CBM
Multiple GEM structures
S. Bachmann et al, Nucl. Instr. and Meth. A479 (2002) 294
high gain - - high breakdown limit
- 10 - 18/04/23 CBM Muon Detection Workshop, GSI Darmstadt, October 16 – 18, 2006 CBM
GEM high rates capability
The total length of the detected signal corresponds to the electron drift time in the induction gap:
Full Width 20 ns(for 2 mm gap)
FAST ELECTRON SIGNAL (NO ION TAIL)
taken from Sauli et al.: http://www.cern.ch/GDD
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GEM high rates capability > 105 Hz/mm2
taken from Sauli et al.: http://www.cern.ch/GDD
- 12 - 18/04/23 CBM Muon Detection Workshop, GSI Darmstadt, October 16 – 18, 2006 CBM
Towards a Micropatterned Muon Chamber
In contrast to Silicon, gas detectors allow for gain (fudge factor)
As learned yesterday, we expect to get at maximum (close to the axis) 1 Track/cm2/event with a 1 MHz event rate.
too much for wire chambers but comfortable for micro pattern detectors such as GEMs (limit beyond 10 MHz/ cm2)
Mostly MIPs, but should expect all kinds of garbage (e.g. neutrons)!
First Muon chamber measures about 2m in diameter, A~3m2
Is it feasible to step from Silicon strips in the STS to a micro patterned gas detector as first Muon chamber...
... employing the same readout front-end ?
Model a Readout System
- 13 - 18/04/23 CBM Muon Detection Workshop, GSI Darmstadt, October 16 – 18, 2006 CBM
Have a look at a Silicon Strip Detector
Sensor thickness ~ 250 to 300 µ
Sensor pitch 50.7 µ
Gap 32.7 µ
Manufacturer quotes1.5 pF/cm strip length
= 11.8
The average strip length will be about 10 to 15 cm,giving 15 to 22.5 pF strip capacitance
- central sensors have shorter strips, longer cables- outer sensors have longer strips, shorter cables- strip area about 5 mm2
- 14 - 18/04/23 CBM Muon Detection Workshop, GSI Darmstadt, October 16 – 18, 2006 CBM
Model Sensor to Scale Capacitance Purely 2D electrostatic problem, 2D Poisson solvers
available, also some analytical solutions
Capacitance scales with ratios of characteristic geometric lengths: strip-gap/strip-width, strip-width/sensor-thickness
Model Silicon strip as a strip-line: get C = 1.23 pF/cm sensor thickness non essential, lower electrode may be abolished
Strip impedance 69 Ohm, signal phase velocity 0.4 c, effective = 6.5
Capacitance scales with effective as
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Gas Detector Scaled from Silicon
With identical, scalable geometry, = 1 or 1.1 get C = 190 fF/cm
Scale readout by a factor of 10 and get the same capacitance: Strip pitch 0.5 mm, sensor thickness 2 - 3 mm
Gems at 2 to 3 mm distance have no influence on capacitance
Strip impedance 175 to 200 Ohm
Strip width of 180 µ comfortably realizable
Feasible strip length for silicon readout electronics: 65 cm
- 16 - 18/04/23 CBM Muon Detection Workshop, GSI Darmstadt, October 16 – 18, 2006 CBM
Corresponding Detector Strip Area
65 cm of 0.5 mm strip pitch corresponds to 3.25 cm2
Central region needs higher granularity, up by a factor of about 10 in order to avoid hit pile-up. Cap. = 1.2 pF, so 10 pF may be spend on cabling, A = 0.33 cm2
Lateral regions have little rate, so may be operated with higher strip areas.
What is the necessary resolution? Here we need some input from the tracking side!
- 17 - 18/04/23 CBM Muon Detection Workshop, GSI Darmstadt, October 16 – 18, 2006 CBM
Proposal for a CBM First Muon Chamber
GEM 1GEM 2
RO Strips
Drift Region
Drift
Signal channeling electrode
MIPs: dE/dx for Argon at normal pressure 2.7 keV/cm, giving 90 e-ion pairs per cm.
For Silicon sensors, a MIP gives about 50 000 e-hole pairs. Parallax and local tacklet tracking may demand for higher
granularity in drift-time detection, resulting in 1 mm drift resolution. Q = 9 e-/mm
need quite some gain for detection two GEM layers to guarantee gain of 1000 to 10 000.
- 18 - 18/04/23 CBM Muon Detection Workshop, GSI Darmstadt, October 16 – 18, 2006 CBM
Conclusion A GEM gas chamber appears to be a suited solution for the first Muon
chamber. GEMs nicely match the specified rate capability of 106
Hz/cm2.
Detector capacitance may be chosen to perfectly adapt to Silicon
optimized readout electronics.
The Gas detector wins with a factor of 6.5 effective over Silicon,
allowing for much longer structures (longer by the same factor of 6.5).
Lack of signal intensity needs to be compensated for by gain
The double GEM layer allows for gain up to 10 000 with limited sparking
probability.