GEM at CERN seminar

GEM at CERNGEM at CERN

Leszek Ropelewski CERN PHLeszek Ropelewski CERN PH--DT2DT2--ST & TOTEMST & TOTEM

OutlineOutline

• Introduction to Gas Electron Amplifier• Main Properties• TOTEM• Cylindrical GEM for NA-49 Future• Other Applications and Perspectives• Remarks about Future of GEM Technology at CERN

New and very old resultsLimited to only GDD activities

MicroStrip Gas ChamberMicroStrip Gas Chamber

A. OedNucl. Instr. and Meth. A263 (1988) 351.

Lift-off technique

Semiconductor industry technology:

PhotolithographyEtchingCoatingDoping


Typical distance betweenwires limited to 1 mmdue to mechanical andelectrostatic forces

Typical distancebetween anodes 200 μmthanks to semiconductoretching technology

MWPC MSGC

anode cathodecathode

A. OedNucl. Instr. and Meth. A263 (1988) 351.

Rate capability limit due to spacecharge overcome by increased amplifying cell granularity

Single Wire Proportional ChamberSingle Wire Proportional Chamber

Electrons liberated by ionization drift towardsthe anode wire. Electrical field close to the wire (typical wire Ø~few tens of μm) is sufficiently high for electrons(above 10 kV/cm) to gain enough energy to ionizefurther → avalanche – exponential increase ofnumber of electron ion pairs.

Cylindrical geometry is not the only one able to generate strong electric field:

parallel plate strip hole groove

( )

arCVrV

rCVrE

ln2

)(

12

0

0

0

0

⋅=

⋅=

πε

πε C – capacitance/unit lengthanode

e-

primary electron

MicroStrip Gas ChamberMicroStrip Gas ChamberSurface chargingBulk resistivity of the support materialSurface modification by doping or deposition

AgeingGas, Gas system, MSGC support, Construction material

Discharges

Charge pre-amplification for ionization released in high field close to cathode

MSGC: Discharge mechanisms

Field emission from the cathode edge

Very high ionization release:avalanche size exceeds Reather’s limit

Q ~ 107


Uncoated MSGCCoated MSGC

Electric field strength close to support plane in MSGC

GEM: Gas Electron MultiplierGEM: Gas Electron MultiplierThin metal-coated polymer foil pierced by a high density of holes (50-100/mm2)Typical geometry: 5 μm Cu on 50 μm Kapton, 70 μm holes at 140 μm pitch

F. Sauli, Nucl. Instrum. Methods A386(1997)531

70 µm

140 µm

GEM PrincipleGEM Principle

70 µm

55 µm

5 µm

50 µm

GEM hole cross sectionAvalanche simulation

ElectronsElectrons

IonsIons

60 %

40 %

Single GEM PerformancesSingle GEM Performances

0

50

100

150

200

250

0 100 200 300 400 500 600 700 800Pulse Height (ADC channels)

Cou

nts

GEM H2+PCAr-DME 80-20ΔV

GEM= 520 V (Gain ~5000)

GEM H2+PC X Pulse Height

102

103

104

200 300 400 500 600 700ΔVGEM

(V)

SINGLE GEM+PCB

Eff. Gain-Vgem Ar-CO2-DME

Ar-DME 70-30

Ar-CO2 70-30

Effe

ctiv

e G

ain

Gain

R. Bouclier et al NIM A 396 (1997) 50

Energy resolution5.9 keV Fe55~20% fwhm

Ar-

CO2

70-3

0

S4S4S3S3S2S2S1S1

Induction gap

e-

e-

I+

Electrons are collected on patterned readout board. A fast signal can be detected on the lower GEM electrode for triggering or energy discrimination. All readout electrodes are at ground potential.Positive ions partially collected on the GEM electrodes.

50 μm Kapton5 μm Cu both sides

Photoresist coating, masking and exposureto UV light

Metal etching

Kapton etching

Second masking

Metal etching and cleaning

Rui De OliveiraCERN-EST-DEM

GEM ManufacturingGEM Manufacturing


30 cm

10 cm

33 cm

30 cm

10 cm

1500÷2000 foils manufactured at CERN 1 cm2 to 1000 cm2

30-200 µm holes, 50-300 µm pitch

Wide rage of shapes and sizesWide rage of shapes and sizes

Art of Kapton EtchingArt of Kapton Etching

GEM GEM –– Gas Electron MultiplierGas Electron Multiplier

A. Bressan et al, Nucl. Instr. and Meth. A425(1999)254

Full decoupling of the charge amplification structure from the charge collection andreadout structure.Both structures can be optimizedindependently !

All detectors use three GEM foils in cascade for amplificationto minimize discharge probability by reducing field strength.

Cartesian Cartesian Compass, LHCbCompass, LHCb

Small angleSmall angle

Hexaboard, padsHexaboard, padsMICEMICE

MixedMixedTotemTotem

CompassCompass TotemTotem

33 cm

NA49NA49--futurefuture

Charge correlation (Cartesian readout)

30 cm20 cm

MultiMulti--GEM DetectorsGEM DetectorsDischarge Probability on Exposure to 5 MeV Alphas

Multiple structures provide equal gain at lower voltage.Discharge probability on exposure to α particles is strongly reduced.

S. Bachmann et al Nucl. Instr. and Meth. A479(2002)294

GEM foils for COMPASS (31x31 cm2), 12-sectors + beam killer

~ 100 foils produced22 Triple-GEM detectors running

Sector separation

Voltage-controlled Central disk

HV sectorsHV sectors


σ = 69.6 µm

4.5 ns4.8 ns

5.3 ns9.7 ns

Rate capability

Space resolution

Time resolution

GAIN ~ 104

Ar-CO2 70-30

1 mC~2.1010 min.ion. particles

Ageing properties

2x106 H/mm2

APV with protection

Test termination card

u (mm)-150 -100 -50 0 50 100 150

0.7

0.75

0.8

0.85

0.9

0.95

1

GM06UEfficiency

128 channels


TOTEM DetectorsTOTEM Detectors

RP1RP1 (RP2)(RP2) RP3RP3

220 m220 m(180 m)(180 m)147 m147 m

Roman Pots:Roman Pots:

~14 m

CMSCMST1: 3.1 < |η| < 4.7

T2: 5.3 < |η| < 6.5

10.5 m T1T1 T2T2

HF

Inelastic Telescopes:Inelastic Telescopes:

to measure total pp cross section and study elastic scattering and diffractive dissociation at the LHC

T2 GEMT2 GEMCASTORCASTOR

TableTable

CollarCollarT2 TelescopeT2 Telescope

10 detector planes on each side of IP

TOTEM GEM : Concept and DesignTOTEM GEM : Concept and DesignDetector requirements:Detector requirements:

Rate Capability - Charge particle rates 104 p mm-2s-1 at L = 1033 cm-2s-1

Ageing - 1 year of continuous operation 1011 p mm-2 -> 7 mC mm-2

Discharges - at probability of 10-12/part. -> 10 disch. cm-2 year-1

Time Resolution - < 10 nsSpace Resolution - < 100 µmEfficiency - > 97 %

TOTEM GEM Final Detector ModuleTOTEM GEM Final Detector Module

Gas in/outHV cables

HV divider

Cooling

Support

Mother board

VFAT card

VFAT card

TOTEM READOUT BOARD:Radial strips (accurate track’s angle)Pad matrix (fast trigger)

TOTEM GEM TOTEM GEM -- Readout BoardReadout Board

50 μm Polyimide

25 μm Polyimide

125 μm FR4

15 μm CuEpoxy glue

5 μm Cu10 μm CuEpoxy glue

Ni Au15 μm Cu

TOTEM Readout

radial stripspads bonding contactfor pads

Readout board

GEM foils

Frames, spacers and supports

HV and electronics

Detector ComponentsDetector Components

GEM Detector AssemblyGEM Detector Assembly

Optical Scanning of GEM FoilsOptical Scanning of GEM Foils

• scanning in mixed mode (transparent + reflective)

• blue diffuser produces a color contrast between the holes and copper surfaces

1.8 million GEM holes

defects, dust, scratches, etc

scanned pictures can be analyzed by using fitting algorithms to count anomalies and to register their coordinates

The worst foil so far: Blue curve shows all the seen objects; the red one only the ”roughly round ones” (e.g. scratches are filtered out). The number of defects (red ones > 80) was 240, while only 40 were found under visual inspection (see previous slide).

AIM:a quantitative measure of the quality of GEM foils

Analysis of defects and hole sizesAnalysis of defects and hole sizes

GEM Foil DefectsGEM Foil Defects

TOTEM GEM Readout Board TestTOTEM GEM Readout Board Test

Quality test forcontinuity and shorts –Capacitance measurementbetween channels forstrips and pads

Laboratory TestsLaboratory Tests

Lab performance as expected:

Gas gain 104

Charge sharingpad signal 10% higher – advantage for higher S/N for trigger electronics

Good charge correlation

Good energy resolution

0 100 200 300 400 500 600 700

0

100

200

300

400

500

StripAmpVsStrip_Proj01_Smpl02

Entries 5194Mean x 370.9Mean y 24.52RMS x 221.2RMS y 11.31

StripAmpVsStrip_Proj01_Smpl02

Entries 5194Mean x 370.9Mean y 24.52RMS x 221.2RMS y 11.31

GM01 Strip amplitude projection vs strip

X5 X5 –– beam testbeam test

padsstrips

Noise distribution

Compass APV hybrids

All strips and one (out of four ) sectors of pads connected to COMPASS APV hybrids

Readout chain from COMPASS

All channels readout

Latency and HV scan

Good noise-signal peak separation

pads strips

Signal distribution

X5 X5 –– beam test with APV electronicsbeam test with APV electronics

Pads chargePads chargeStrips chargeStrips charge

Strips cluster size Strips cluster size Strips Strips -- Pads charge correlationPads charge correlation

VFAT chip 128 channels with front end and comparator with adjustable thresholdVFAT/CC design team: P. Aspell, G. Anelli, J. Kaplon, K. Kloukinas, W. Snoeys, H. Mugnier, P. Chalmet (CERN-C4i)

ElectronicsElectronics

VFAT chipDesigned by PH-MIC in collaboration with C4I

Roman Pot Silicon

T1 CSCT2 GEM

trigger

Coincidence Chip

CMS Counting Room

& Global Trigger

Gigabit Optical Link

data

SRAM1 SRAM2

VFAT Front End SpecsVFAT Front End Specs

• Pulse Gain at discriminator input; 53mV/fC (simulated for maximum charge collection time)

• Integral nonlinearity error: • <1% for input charge 0 to 12fC• <3% for input charge 0 to 16fC• Peaking time; 22.5ns (simulated for 3.5fC input charge and maximum charge

collection time)• Power consumption for nominal bias condition; 1.9mW/channel (250mW for

whole front end)• Noise performance for nominal bias condition;• <1000 e- rms for Cinput = 10pF• <1400 e- rms for Cinput = 20pF• Maximum load of the analogue test outputs; <5pF

APV chip

COMPASS TOTEM

Protection Circuit

Discharge Protection CircuitDischarge Protection Circuit

APV VFAT

Totemino @ SPS H8Totemino @ SPS H8

10 detectors in 5 pairs back to back8 assembled in Helsinki1 G&A1 CERN

Electronics capable to read 16 VFAT hybrids2 hybrids/detector connected to pads & strips

Totemino ElectronicsTotemino Electronics

VFAT & GEMVFAT & GEM

S-curve VFAT only S-curve GEM pad noisy S-curve GEM pad

Pads capacitance Pads thresholds noisy Pads thresholds

Totemino Totemino –– first beam profilesfirst beam profiles

StripsStripsPadsPads

PadsPads

PadsPads

Latency scanLatency scan

Time Slots 25 nsTime Slots 25 ns

Totemino Totemino –– first tracksfirst tracks

2 different detectorshit correlation on strips

TOTEM Inelastic TelescopesTOTEM Inelastic Telescopes

~3 m

T1: Cathode Strip ChambersT1: Cathode Strip Chambers~14 m

CMSCMST1: 3.1 < |η| < 4.7

T2: 5.3 < |η| < 6.5

10.5 m T1T1 T2T2

HF

Inelastic Telescopes:Inelastic Telescopes:

T2: GEMsT2: GEMs

~ 0.5 m

T1 Upgrade T1 Upgrade -- Large GEM DetectorsLarge GEM DetectorsGEM foil size is limited by :

Starting raw material dimensions

Precision of 2 masks alignment

mean pad size ~ 2 cm2

16x64 7x7 mm2 —› 38x38 mm2

180 cm !

Emilio Radicioni et al.

50 μm Kapton5 μm Cu both sides

Photoresist coating, masking and exposureto UV light

Metal etching

Kapton etching

Second masking

Metal etching and cleaning


Double mask process

Single mask process

Positively tested for:

Gas gainCharging up process (asymmetry)Maximum gain in presence of HIPs

Cylindrical GEM for NA49Cylindrical GEM for NA49--FutureFuture

COMPASS 31x31 cm2

GEM foil

Cylindrical GEM DesignCylindrical GEM Design

Protection Circuit

APV with protection

Test termination card

2D Cartesian readout400 μm pitch

Cylindrical GEM Readout Board DesignCylindrical GEM Readout Board Design

128 channels

Cylindrical GEM Mechanical Parts and ToolsCylindrical GEM Mechanical Parts and Tools

Cylindrical GEM Assembly 1Cylindrical GEM Assembly 1Drift ElectrodeDrift Electrode

Cylindrical GEM Assembly 2Cylindrical GEM Assembly 2GEM foilsGEM foils

Cylindrical GEM Assembly 3Cylindrical GEM Assembly 3

Mechanical Prototype was tested for:Mechanical Prototype was tested for:

Mechanical stabilityGas tightness

Final detector finalized:Final detector finalized:

Completed at the end of June.

Cylindrical GEM PreparationCylindrical GEM Preparation

Lab work:

HV board

Electronic noise reduction

Nitrogen hut (r. humidity ~90%)(h.v. board and/or relatively thin window)

Photograph of a complete ARC setup: (1) PCMIO Interface, to be plugged into anISA slot of the PC motherboard, (2) 50 pin flat cable, (3) ARC board, (4) 26 pin

twisted pair flat cable, (5) ARC front-end adapter, (6) Hybrid-to-VUTRI adaptercard, (7) front-end hybrid, (8) power supply cable for the ARC board.

The ARC SystemThe ARC System

1-2 128 channels APV hybrids Shortcomings: Old fast PC, small distance to detector

Cylindrical GEM Lab TestCylindrical GEM Lab Test

Lab performance as planar detector:

Gas gain

Charge sharing

Charge correlation

Energy resolution

Mechanical and electrical stability

Cylindrical GEM Beam Test @ SPS H2Cylindrical GEM Beam Test @ SPS H2Hadron beam at 3 106 p/spill

Absorption radiography with GEM (8 keV XAbsorption radiography with GEM (8 keV X--rays)rays)

Trigger from the bottom electrode of GEM.

S. Bachmann et al, Nucl. Instr. and Meth. A471(2001)115

Absorption radiography with GEM (8 keV XAbsorption radiography with GEM (8 keV X--rays)rays)

UV Light Detection (RICH)UV Light Detection (RICH)

UV transparent Quartz window

200 µm

D. Mormann et al, Nucl. Instr. and Meth. A478(2002)230

T. Meinschad, L. Ropelewski and F. Sauli, Nucl. Instr. and Meth. A535(2004)324

Single photoelectron p.h. spectrum

Hexaboard readout:matrix of hexagonal pads interconnected along three projections at 120º

U

V

W

S. Bachmann et al Nucl. Instr. and Meth. A 478 (2002) 104F. Sauli, RICH04 (Playa del Carmen, Nov. 30-Dec. 5, 2004 Subm. Nucl. Instr. And Meth.

1.1 mm

2.4 mm

1.3 mm

Hexaboard Readout

Two-photon event

31 cm

GEM Foil Material Budget ReductionGEM Foil Material Budget ReductionBy reducing Cu layer thickness 5 By reducing Cu layer thickness 5 μμm m ――> 1 > 1 μμmm

Detector element (material)

Rad. length [cm]

x/X0

Si 300 μm 9.4 3.2 10-3

Cu 5 μm 1.44 3.5 10-4

Kapton 50 μm 8.57 1.8 10-4

Argon 1 cm 11762 0.85 10-4

Triple GEM standard:5 x Kapton 50 μm7 x Cu 5 μmArgon 7 mm

3.4 10-3

Triple GEM light:5 x Kapton 50 μm7 x Cu 1 μmArgon 7 mm

1.5 10-3

standard

light

GEM TPCGEM TPC

GEM TPCVERTEX

GEM readout for the Time Projection Chamber (GEM-TPC)

International Linear Collider Detector

ILC TPC R&D groups (~ 40)

http://alephwww.mppmu.mpg.de/~settles/tpc/welcome3.html

Narrow pad response function: Δs ~ 1 mmFast signals (no ion tail): ΔT~20 nsVery good multi-track resolution: ΔV ~ 1 mm3

(Standard MWPC TPC ~ 1 cm3)Strong ion feedback suppressionNo ExB distortionsFreedom in end-cap shapesRobustness

GEM TPCGEM TPC

Small charge spread:

Optimization of pad geometry

Resistive anode

Small pads & high densityintegrated pixel electronics

Ion feedback reduction:

Gas composition

Spill structure

Geometry

New amplifier structures

Mesh gating

Low voltage Gem gating ->

Low voltage GEM electron transmission

PerspectivesPerspectives

Tracking and triggering (LHCb & TOTEM)Tracking and triggering (LHCb & TOTEM)TPC end cap readoutTPC end cap readoutXX--ray radiographyray radiographyUV light detectionUV light detectionParallax error free detectorParallax error free detectorHadron blindHadron blindNeutron detectionNeutron detectionOptical GEMOptical GEMCryogenic detectorsCryogenic detectorsTwoTwo--phase detectorsphase detectorsHigh resolution detectors integrated with pixel CMOS chipsHigh resolution detectors integrated with pixel CMOS chipsNon planar large acceptance detectorsNon planar large acceptance detectorsLight detectors Light detectors –– mass reductionmass reductionNew readout structures adopted to experimental needsNew readout structures adopted to experimental needsLarge size detectorsLarge size detectorsRadiation hardness of assembly materialsRadiation hardness of assembly materialsIndustrialization of the mass productionIndustrialization of the mass productionMedical applicationsMedical applications

Single mask process

Double mask process

http://gdd.web.cern.ch/GDD/http://gdd.web.cern.ch/GDD/

GDD population evolutionGDD population evolutionWires 80sWires 80s

Strips 90sStrips 90s

Holes 00sHoles 00s

Positives:

BudgetNew gas detector labStudent(s)

Detector DesignDetector DesignDT2DT2

Component ProductionComponent ProductionTSTS--DEM DEM --> industry> industry

Component QualityComponent QualityControlControl

DT2 & institutes DT2 & institutes --> TS> TS--DEM DEM --> > industryindustry

Detector AssemblyDetector AssemblyDT2 DT2 --> institutes > institutes --> industry> industry

Detector TestDetector TestDT2 DT2 --> institutes> institutes

GEM Detectors at CERNGEM Detectors at CERN

GEM Detectors at CERNGEM Detectors at CERN

ElectronicsElectronicsMICMIC

Detector SimulationsDetector SimulationsDT2 DT2 --> SFT> SFT

Technology DisseminationTechnology DisseminationDT2 DT2 --> DSU> DSU--TTTT

APVAPVVFATVFATGP5GP5ALTROALTRO

GarfieldGarfieldMaxwellMaxwellMagboltz Magboltz Imonte Imonte HeedHeed

PANalyticalPANalytical3M3MTechEtchTechEtchTechtraTechtraG&AG&A

In 2 weeks meeting of all players to define roles and objectives ofbetter cooperation and use of available resources – perhaps come withthe proposal of wider collaboration on Micropattern Gas Detectors.

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GEM at CERN seminar