a. buzulutskov

A. Buzulutskov, Instr08, 1/03/08 1

A. Buzulutskov

Budker Institute of Nuclear Physics, Novosibirsk

Radiation Detectors Based on Gas Electron Multipliers

Outline- Principles and basic properties of GEMs- Cryogenic avalanche detectors- Tracking detectors- Other detectors - Summary


1. High rate capability2. High gain3. Low discharge rate4. High space resolution5. High time resolution6. Reasonable energy resolution7. Low ageing rate8. Low material budget9. Geometrical flexibility10.Variety of readout structures11.Ion backflow reduction12.Photon feedback reduction13.Operation in pure noble gases14.Operation at cryogenic temperatures15.Operation in two-phase mode16.Low noise17.Coupling to photocathodes

Gas Electron Multiplier (GEM) properties

GEM: Gas Electron Multiplier, invented by F.Sauli in 1996 [F.Sauli, NIM A 386(1997)531]


Operation principles

Triple-GEM structure[Novosibirsk & Weizmann]

Field pattern [GDD-CERN]

Field strength along hole axis at different hole diameters [GDD-CERN]

Real gain

Effective gain

Effective and real GEM gain [GDD-CERN]

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


Other hole-type structures:Micro-hole and strip plate (MHSP) [Coimbra]

[Veloso et al., Rev. Sci. Instr. 71(2000)2371]

- Amplification occurs first in the hole and then near the microstrip anodeMHSP: - is two-stage structure and therefore has higher gain than single GEM - has lower ion backflow- can be used both independently and as stages of a multistage GEM


Other hole-type structures:Thick GEM (THGEM) [Weizmann, CERN]

- 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

1mm

30 mm

Hole diameter d = 0.3 - 1 Hole diameter d = 0.3 - 1 mmmmPitch a = 0.7- 7 Pitch a = 0.7- 7 mmmmThickness t = 0.4 - 3 Thickness t = 0.4 - 3 mmmm

[Shalem et al. NIM A558 (2006) 475]

Manufactured by standard PCB techniques of precise drilling in G10 (and other materials) and Cu etching.

See A. Breskin talk


Other hole-type structures:Thick GEM with resistive electrodes (RETHGEM)

[CERN]

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

[Oliveira et al. NIM A 576 (2007) 362]

Photo of RETHGEM made of resistive kapton

Photo of RETHGEM produced using screen printing technology [Peskov et al.]


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]


Space, time and energy resolution

Space resolution [COMPASS]

= 69.6 µm400m pitch

4.5 ns4.8 ns

5.3 ns9.7 ns

Time resolution for tracks [Frascatti] Time resolution for

photons in 3GEM-based GPM in CF4[Weizmann & Novosibirsk]

Space resolution [GDD-CERN]

= 40 µm200m pitch

= 2 ns

Energy resolution [GDD-CERN]


Rate capability and ageing

Single-GEM [GDD-CERN]

Triple-GEM [Frascatti]

Triple-GEM [Frascatti]


Discharge rate

Discharge probability as a function of gain in three-stage structure, 3GEM, and two-stage structures, 2GEM and GEM+Groove. Test at PSI 300 MeV/c pion beam. [Novosibirsk & CERN]

Efficiency and signal-to-noise ratio as functions of gain in triple GEM with 2D readout at PSI pion beam [Novosibirsk]

- Two-stage structures do not provide efficient operation before the onset of discharges - Only the triple-GEM satisfies this criterion


Operation in pure noble gases: GEMs

High gain of the triple-GEM in Ar-based mixtures at 1 atm [Novosibirsk & Weizmann]

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]

Unique ability of GEM-like structures No other gas avalanche detectors can do this !

High gain of the triple-GEM in noble gases at cryogenic temperatures [Novosibirsk & Columbia Un.]


Operation in pure noble gases: MHSPs and THGEMs

See A. Breskin talk

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]

RETHGEM gain in pure Ar at 1 atm: - High gain both at room and cryogenic temperatures [Peskov et al. IEEE TNS 50(2007)1784]


Ion backflow (IBF)

- IBF is independent of gas mixture - IBF is linear function of the drift field- IFB is a polynomial function of the gain

[Novosibirsk]

Reduction of ion backflow in high magnetic field in the triple-GEM. Gain 104, drift field 0.2 kV/cm, asymmetric transfer fields [Aachen]

See A. Lyashenko talk


GEM in current, ready for operation and future experiments

Tracking experiments:COMPASSLHCb muon detectorSystem of Tagged Electrons for KEDR TOTEM telescopeNA49 upgradeCLOE2 vertex detectorILC TPC

Cryogenic experiments for neutrino and dark matter physics:E-bubble ArDMSLICECoherent neutrino scattering

Cherenkov detectors:Hadron Blind Detector for PHENIX experiment at RHIC

Synchrotron radiation experiments:OD4

Current R&D:Two-phase avalanche detectorsHigh-pressure detectors MHSPTHGEMRETHGEMPixel readoutGas PMTMedical applications


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]

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)

Need for detector recording both ionization and scintillation signal with a threshold of ~10 keV (200 electrons)


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

Two-phase avalanche detectors The concept and experimental setup [Novosibirsk]


GEM-based two-phase avalanche detectors: properties [Novosibirsk]

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 single electron spectra in two-phase Ar:- At gains>4000 good separation from electronic noises- Described by exponential function

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 correlated to each other.

See D. Pavlyuchenko talk See F. Balau poster


Triple-GEM vs. double-THGEM in two-phase Ar avalanche detectors [Novosibirsk & Weizmann]

Stable operation in two-phase Ar:- Thin triple-GEM with gains reaching 104

- Double-THGEM with gains reaching 3x103

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.


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


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


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


Cryogenic avalanche detectors at low T: solution of the gain drop problem using Penning mixtures in

H2

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]

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]

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]


Tracking detectors: COMPASS [CERN]

- 22 triple-GEM chambers- 31x31 cm2 active area- Mixture Ar/CO2- 2D readout: perpendicular strips- 400 m strip pitch- Space resolution 70 m- Time resolution 12 ns- 25 kHz/mm2- Operation in 2002-2006

Uniformity of tracking efficiency


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


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


Tracking detectors: TOTEM [CERN]

Forward tracker in CMS

- 40 half-moon triple-GEM chambers- 30 cm diameter- 2D readout with radial strips and pads


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


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]


Pixel readout

See D. Attie talk

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

[Bamberger et al. / NIM A 573 (2007) 361]

MPGD with ultimate space resolution using integrated pixel electronic readout

- Medpix2 chip: 256x256 pixels 55 µm pitch- Originally developed for X-ray imaging- Digital readout: preamp / discriminator - Pixel noise 150 e


Pixel readout

Concept of pixel readout for X-ray polarimetry by tracking the photoelectron direction

Single-GEM detector with CMOS chip readout

[Bellazzini et al. / NIM A 572 (2007) 160]

MPGD with ultimate space resolution using integrated pixel electronic 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


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


GEM-based gas photomultupliers (GPM)

N/A


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 !


GEM physics: physical processes


GEM physics: ionization coefficients

- 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]

- 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]

Obtained due to unique GEM ability to effectively operate in pure noble gases at high pressures and low temperatures


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?


Cryogenic two-phase Ar or Xe avalanche detectorsMotivation: medical applications

LXeGEM-based two-phase Xe or Kr avalanche detector for PET- Solving parallax problem- Superior spatial resolution if to use GEM readoutBudker Institute: CRDF grant RP1-2550 (2003)

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 neededBudker Institute: INTAS grant 04-78-6744 (2005), Presented at SNIC06, http://www.conf.slac.stanford.edu/snic/.

Two-phase Xe detector for PETChen & Bolozdynya, US patent 5665971 (1997)


- 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

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.

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.

Electron emission through liquid-gas interface [Novosibirsk]

a. buzulutskov

Documents

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cerntriplegem gain

gain characteristicstriplegem

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real gem gain gddcerna

thick gem thgem weizmann

holetype structures

hole axis