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A. Buzulutskov

Radiation Detectors Based on Gas Electron Multipliers. A. Buzulutskov. Budker Institute of Nuclear Physics, Novosibirsk. Outline - Principles and basic properties of GEMs - Cryogenic avalanche detectors - Tracking detectors - Other detectors - Summary.

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A. Buzulutskov

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  1. Radiation Detectors Based on Gas Electron Multipliers A. Buzulutskov Budker Institute of Nuclear Physics, Novosibirsk Outline - Principles and basic properties of GEMs - Cryogenic avalanche detectors - Tracking detectors - Other detectors - Summary A. Buzulutskov, Instr08, 1/03/08

  2. Gas Electron Multiplier (GEM) properties GEM: Gas Electron Multiplier, invented by F.Sauli in 1996 [F.Sauli, NIM A 386(1997)531] • High rate capability • High gain • Low discharge rate • High space resolution • High time resolution • Reasonable energy resolution • Low ageing rate • Low material budget • Geometrical flexibility • Variety of readout structures • Ion backflow reduction • Photon feedback reduction • Operation in pure noble gases • Operation at cryogenic temperatures • Operation in two-phase mode • Low noise • Coupling to photocathodes A. Buzulutskov, Instr08, 1/03/08

  3. Operation principles Real gain Effective gain Field strength along hole axis at different hole diameters [GDD-CERN] Effective and real GEM gain [GDD-CERN] Field pattern [GDD-CERN] Triple-GEM structure[Novosibirsk & Weizmann] A. Buzulutskov, Instr08, 1/03/08

  4. Double mask process requires +-2 mm accuracy and therefore is possible for up to 40x40 cm2 area A. Buzulutskov, Instr08, 1/03/08

  5. Other hole-type structures:Micro-hole and strip plate (MHSP) [Coimbra] [Veloso et al., Rev. Sci. Instr. 71(2000)2371] • -Amplification occurs first in thehole and then near the microstrip anode • MHSP: • is two-stage structure and therefore has higher gain than single GEM • has lower ion backflow • can be usedboth independently and as stages of a multistage GEM A. Buzulutskov, Instr08, 1/03/08

  6. Other hole-type structures:Thick GEM (THGEM) [Weizmann, CERN] 1mm Hole diameter d = 0.3 - 1 mm Pitch a = 0.7- 7 mm Thickness t = 0.4 - 3 mm See A. Breskin talk 30 mm [Shalem et al. NIM A558 (2006) 475] Manufactured by standard PCB techniques of precise drilling in G10 (and other materials) and Cu etching. • Easy to produce • Higher gain in a single stage structure due to larger thickness and rim • Higher resistance to discharges due to smaller hole number and larger hole length • The possibility of cascading • THGEM can replace GEM when the high space resolution and high rate capability is not necessary A. Buzulutskov, Instr08, 1/03/08

  7. Other hole-type structures:Thick GEM with resistive electrodes (RETHGEM) [CERN] Photo of RETHGEM made of resistive kapton [Oliveira et al. NIM A 576 (2007) 362] Photo of RETHGEM produced using screen printing technology [Peskov et al.] RETHGEM has the same properties as that of THGEM + even higher resistance to discharges due to lower discharge energy and higher resistance of electrode material evaporated on hole surface during discharge A. Buzulutskov, Instr08, 1/03/08

  8. Gain characteristics Triple-GEM vs. double- and single-GEM gainDischarge probability induced by alfa-particles[GDD-CERN] Triple-GEM gain in mixtures with quenching additives [Novosibirsk & Weizmann] A. Buzulutskov, Instr08, 1/03/08

  9. Space, time and energy resolution 5.3 ns 9.7 ns • = 2 ns • = 40 µm 200mm pitch 4.8 ns 4.5 ns • = 69.6 µm 400mm pitch Space resolution [GDD-CERN] Time resolution for tracks [Frascatti] Time resolution for photons in 3GEM-based GPM in CF4[Weizmann & Novosibirsk] Energy resolution [GDD-CERN] Space resolution [COMPASS] A. Buzulutskov, Instr08, 1/03/08

  10. Rate capability and ageing Single-GEM [GDD-CERN] Triple-GEM [Frascatti] A. Buzulutskov, Instr08, 1/03/08 Triple-GEM [Frascatti]

  11. Discharge rate Efficiency and signal-to-noise ratio as functions of gain in triple GEM with 2D readout at PSI pion beam [Novosibirsk] Discharge probability as a function of gain in three-stage structure, 3GEM, and two-stage structures, 2GEM and GEM+m-Groove. Test at PSI 300 MeV/c pion beam.[Novosibirsk & CERN] - Two-stage structures do not provide efficient operation beforethe onset of discharges - Only the triple-GEM satisfies this criterion A. Buzulutskov, Instr08, 1/03/08

  12. Operation in pure noble gases: GEMs Unique ability of GEM-like structures No other gas avalanche detectors can do this ! Triple-GEM gain at high pressures: - High gain in light noble gases up to 15 atm- High gain in heavy noble gases at 1 atm- Fast gain decrease with pressure in heavy noble gases [Novosibirsk] High gain of the triple-GEM in Ar-based mixtures at 1 atm [Novosibirsk & Weizmann] High gain of the triple-GEM in noble gases at cryogenic temperatures [Novosibirsk & Columbia Un.] A. Buzulutskov, Instr08, 1/03/08

  13. Operation in pure noble gases: MHSPs and THGEMs See A. Breskin talk RETHGEM gain in pure Ar at 1 atm: - High gain both at room and cryogenic temperatures[Peskov et al. IEEE TNS 50(2007)1784] MHSP gain in pure noble gases at high pressures: - High gain in Ne at all pressures- High gain in heavy noble gases at 1 atm- Slower gain decrease with pressure in heavy noble gases compared to the triple-GEM[Coimbra & Weizmann] THGEM gain in pure Ar and Xe: - High gain at 1 atm- Fast gain decrease with pressure[Weizmann & Coimbra] A. Buzulutskov, Instr08, 1/03/08

  14. Ion backflow (IBF) See A. Lyashenko talk Reduction of ion backflow in high magnetic field in the triple-GEM. Gain 104, drift field 0.2 kV/cm, asymmetric transfer fields [Aachen] • IBF is independent of gas mixture - IBF is linear function of the drift field- IFB is a polynomial function of the gain[Novosibirsk] A. Buzulutskov, Instr08, 1/03/08

  15. GEM in current, ready for operation and future experiments Cryogenic experiments for neutrino and dark matter physics:E-bubble ArDMSLICECoherent neutrino scattering Tracking experiments:COMPASSLHCb muon detectorSystem of Tagged Electrons for KEDRTOTEM telescopeNA49 upgradeCLOE2 vertex detectorILC TPC Cherenkov detectors:Hadron Blind Detector forPHENIX experiment at RHIC Current R&D:Two-phase avalanche detectorsHigh-pressure detectors MHSPTHGEMRETHGEMPixel readoutGas PMTMedical applications Synchrotron radiation experiments:OD4 A. Buzulutskov, Instr08, 1/03/08

  16. Cryogenic two-phase Ar or Xe avalanche detectorsMotivation: dark matter search and coherent neutrino scattering ArDM: Two-phase Ar detectors for dark matter search using THGEM readout [A.Rubbia et al., Eprint hep-ph/0510320] Need for detector recording both ionization and scintillation signal with a threshold of ~10 keV (200 electrons) Two-phase or high-pressure Ar or Xe detectors for coherent neutrino-nucleus scattering [Hagmann & Bernstein, IEEE TNS 51 (2004) 2151] Need for noiseless (1 event/hour/kg) detector with a threshold of 1 e (single-electron counting) A. Buzulutskov, Instr08, 1/03/08

  17. Two-phase avalanche detectors The concept and experimental setup [Novosibirsk] The concept of two-phase avalanche detector with detection both ionization and scintillation signals, using multi-GEM multiplier with CsI photocathode on top of first GEM A. Buzulutskov, Instr08, 1/03/08

  18. GEM-based two-phase avalanche detectors: properties [Novosibirsk] See D. Pavlyuchenko talk See F. Balau poster Triple-GEM gain in two-phase mode: - In Ar: rather high gains are reached, of the order of 104 - In Kr and Xe: moderate gains are reached, about 103 and 200 respectively Triple-GEM pulse-height spectra in two-phase Ar for 60 keV X-rays, neutrons+gammas from 252Cf and single electrons at gains~4000-5000 Triple-GEM with CsI PC in two-phase Ar: Distribution of events in the plane “ionization (S2) vs. scintillation (S1) signal” amplitudes at gain~2500 and drift field 0.25kV/cm. Most events are of the “S1+S2” type where S1 and S2 are observed and correlatedto each other. Triple-GEM single electron spectra in two-phase Ar: - At gains>4000 good separation from electronic noises - Described by exponential function A. Buzulutskov, Instr08, 1/03/08

  19. Triple-GEM vs. double-THGEM in two-phase Ar avalanche detectors [Novosibirsk & Weizmann] See D. Pavlyuchenko talk Typical signal of thin triple-GEM induced by 60 keV X-ray. Fast and slow emission through liquid-gas interface is distinctly seen. Typical signals of double-THGEM induced by 60 keV X-ray, corresponding to 1000 e prior to multiplication, and by cluster of 50 e prior to multiplication. Fast component is not seen due to slow ion movement through holes. Stable operation in two-phase Ar: - Thin triple-GEM with gains reaching 104 - Double-THGEM with gains reaching 3x103 A. Buzulutskov, Instr08, 1/03/08

  20. Cryogenic He and Ne avalanche detectors at low T Motivation: E-bubble project for solar neutrino detection [Columbia Un. & BNL] • 10 tons mass of He or Ne- Excellent (sub-mm) spatial resolution for low energy tracks- To maintain this, need very low diffusion, namely electrons localized in bubbles (e-bubbles)- Need for some gain, obviously in gas phase A. Buzulutskov, Instr08, 1/03/08

  21. Cryogenic avalanche detectors at low T: experimental setup - Developed at Columbia Un. & BNL - Operated in He and Ne - 1.5 l cryogenic chamber - Several UV windows - 3GEM inside [Novosibirsk] - Gas filling through LN2 or LHe reservoir A. Buzulutskov, Instr08, 1/03/08

  22. Cryogenic avalanche detectors at low T: gain drop problem [Columbia Un. & Novosibirsk] In He: - High gains in 3GEM at T > 78 K - At 2.6-20 K the maximum gain drops considerably: it is only few tens at 0.5 g/l and drops further at higher densities In Ne: - High gains in 3GEM at room T - At cryogenic T GEMs could not work at all High gains observed in He and Ne above 78 K are most probably due to Penning effect in uncontrolled impurities, which freeze out at lower T A. Buzulutskov, Instr08, 1/03/08

  23. Cryogenic avalanche detectors at low T: solution of the gain drop problem using Penning mixtures in H2 Ne and He forms Penning mixtures with H2 at low T: - H2 boiling point (20 K) is below that of Ne (27 K) - Energy of metastable Ne state exceeds H2 ionization potential This is a solution of the gain drop problem at low T in Ne. Unfortunately, this does not work for two-phase He, since H2 vapor pressure is too low at He boiling point (4.2 K) [Columbia Un. & Novosibirsk] • Gains in Ne+H2 at 55-57 K • - at density 9 g/l, corresponding to saturated vapor density at Ne boiling point • Rather high gains are observed, as high as 2*104. The maximum gains are not reached here • [Columbia Un. & Novosibirsk] Observation of alfa-tracks in Ne+10-3H2 using CCD optical readout from a single-GEM at 77 K, density of 22g/l (!) and gain>1000 [Galea et al. IEEE NSS Conf. Rec. 2007] Initial ideas based on two-phase detector is transformed to single-phase supercritical fluid due to insufficient gain in vapor phase for He and long trapping time at liquid-gas surface for Ne [Columbia Un. & BNL] A. Buzulutskov, Instr08, 1/03/08

  24. Tracking detectors: COMPASS [CERN] - 22 triple-GEM chambers- 31x31 cm2 active area- Mixture Ar/CO2- 2D readout: perpendicular strips- 400 mm strip pitch- Space resolution 70 mm- Time resolution 12 ns- 25 kHz/mm2- Operation in 2002-2006 Uniformity of tracking efficiency A. Buzulutskov, Instr08, 1/03/08

  25. Tracking detectors: LHCb muon trigger system [Frascatti] - 12 triple-GEM chambers in innermost region of M1- 20x25 cm2 active area- Foil stretching – no spacers- Fast mixture Ar/CO2/CF4 (45/40/15)- Time resolution 4.5 ns- Rates up to 500 kHz/cm2- Radiation hardness 1.8 C/cm2 in 10 years- Gain ~ 6000 Efficiency at test beam A. Buzulutskov, Instr08, 1/03/08

  26. Tracking detectors See L. Shekhtman talk See D. Attie talk System of Tagged Electrons for KEDR- 8 triple-GEM chambers - Active area up to 25x10 cm2- 2D readout with small angle stereo strips ILC TPC A. Buzulutskov, Instr08, 1/03/08

  27. Tracking detectors: TOTEM [CERN] • 40 half-moon triple-GEM chambers- 30 cm diameter- 2D readout with radial strips and pads Forward tracker in CMS A. Buzulutskov, Instr08, 1/03/08

  28. Tracking detectors: cylindrical GEMs NA49 upgrade [CERN] CLOE2 vertex detector [Frascatti] - 5 concentric layers of cylindrical triple-GEM detectors- Diameter 300 mm, active length 350 mm- 1000x350 mm2 GEM active area patch- 3 GEM foils glued together- ~1500 strips • COMPASS 31x31 cm2 GEM foils- 2D readout with orthogonal strips- Special tools A. Buzulutskov, Instr08, 1/03/08

  29. Cherenkov detector at PHENIX: Hadron Blind Detector [BNL & Weizmann] • Windowless Cherenkov counter- CsI PC coated GEMs- CF4 radiator - 24 triple-GEM detectors 23x27 cm2- Pad readout[Woody et al. IEEE NSS Conf. Rec. 2006] A. Buzulutskov, Instr08, 1/03/08

  30. Pixel readout See D. Attie talk MPGD with ultimate space resolution using integrated pixel electronic readout [Bamberger et al. / NIM A 573 (2007) 361] Medipix2 image of the electron track from 106Ru source in Ar-CO2 (70:30). Primary ionization clusters are seen Schematics of triple-GEM detector with Medpix2 chip readout - Medpix2 chip: 256x256 pixels 55 µm pitch- Originally developed for X-ray imaging- Digital readout: preamp / discriminator - Pixel noise 150 e A. Buzulutskov, Instr08, 1/03/08

  31. Pixel readout MPGD with ultimate space resolution using integrated pixel electronic readout [Bellazzini et al. / NIM A 572 (2007) 160] Concept of pixel readout for X-ray polarimetry by tracking the photoelectron direction Single-GEM detector with CMOS chip readout - Dedicated CMOS readout- 300x352 pixels 50 µm pitch hexagonal pads of 15x15 mm2 active area - Digitals readout: pre-amplifier, shaping amplifier, sample and hold, multiplexer- Pixel noise 50 e A. Buzulutskov, Instr08, 1/03/08

  32. Photoelectric gate to reduce ion backflow Photoelectric Gate [Buzulutskov & Bondar JINST 1 (2006) P08006] - Signal transfer efficiency through the gate is 1/30-1/50 in He and Kr and much lower in CF4 Photon Assisted Cascaded Electron Multiplier (PACEM) [Veloso et al., JINST 1 (2006) P08003] - Signal transfer efficiency through the gate is 1/50 in Xe - Since scintillations should be provided, the gate can effectively work in pure noble gases only - At the moment signal transfer efficiency through the gate is not high enough A. Buzulutskov, Instr08, 1/03/08

  33. GEM-based gas photomultupliers (GPM) N/A A. Buzulutskov, Instr08, 1/03/08

  34. Summary • The amount and variety of radiation detectors based on GEMs is amazing. The fields of most active investigations are the following: • - Tracking detectors for colliding beam experiments: high rate and with high space resolution • - Cryogenic avalanche detectors for neutrino and dark matter search experiments, including two-phase detectors • Photon detectors, including Cherenkov detectors • - Micro-pixel electronic readout for precise tracking • - Synchrotron radiation detectors • We may conclude that GEM is the most fruitful successor of previous generations of gas detectors ! A. Buzulutskov, Instr08, 1/03/08

  35. GEM physics: physical processes A. Buzulutskov, Instr08, 1/03/08

  36. GEM physics: ionization coefficients Obtained due to unique GEM ability to effectively operate in pure noble gases at high pressures and low temperatures - Ionization coefficients for ultrapure He and He “purified” by low T (< 20 K) correspond to literature data - That means that the principal avalanche mechanisms at room and low T are the same, namely electron impact ionization - High gains observed in He and Ne above 78 K are most probably due to Penning effect in uncontrolled impurities [Novosibirsk & Columbia Un. & BNL] • Big difference between heavy and light noble gases- Good agreement between high and low pressure data for heavy noble gases- Ionization coefficients in He and Ne obtained at high pressures strongly exceed the coefficients at low pressures available in the literature[Novosibirsk] A. Buzulutskov, Instr08, 1/03/08

  37. High pressure detectors [Novosibirsk] • In mixtures with molecular quenchers the maximum gain decreases quite rapidly with pressure- In the triple-GEM, high gain in light noble gases (He, Ne) up to 15 atm (due to Penning effect on uncontrolled impurities?)- In the triple-GEM, fast gain decrease with pressure in heavy noble gases (due to ion feedback between GEM elements)- However in single-GEM, slow gain decrease with pressure in heavy noble gases: gains of the order of 100 are reached at 10 atm- Very high gains, up to 106 at 10 atm, in Penning mixtures Ar+Xe, Ne+H2, He+N2, He+Kr- MHSP and THGEM are more promising for high pressure detectors? A. Buzulutskov, Instr08, 1/03/08

  38. LXe Cryogenic two-phase Ar or Xe avalanche detectors Motivation: medical applications GEM-based two-phase Xe or Kr avalanche detector for PET - Solving parallax problem - Superior spatial resolution if to use GEM readout Budker Institute: CRDF grant RP1-2550 (2003) Two-phase Xe detector for PET Chen & Bolozdynya, US patent 5665971 (1997) • GEM-based two-phase Ar or Kr avalanche detector for digital radiography with CCD readout • - Robust and cheap readout • Thin (few mm) liquid layer is enough to absorb X-rays • - Primary scintillation detection is not needed • Budker Institute: INTAS grant 04-78-6744 (2005), Presented at SNIC06, http://www.conf.slac.stanford.edu/snic/. A. Buzulutskov, Instr08, 1/03/08

  39. Electron emission through liquid-gas interface [Novosibirsk] Emission characteristics in Xe - Anode pulse-height as a function of electric field in liquid Xe induced by pulsed X-rays, in 3GEM at gain 80. Emission characteristics in Ar and Kr - Anode pulse-height as a function of electric field in the liquid induced by beta-particles: in Ar – in 2GEM at gain 1500; in Kr – in 3GEM at gain 250. - Electron emission from liquid into gas phase has a threshold behavior - Electric field for efficient emission: in Ar by a factor of 2-3 lower than that in Kr and Xe A. Buzulutskov, Instr08, 1/03/08

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