C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________...
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1 C.Shalem et al, IEEE 2004, Rome, October 18 Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico Thick GEM-like multipliers: Thick GEM-like multipliers: a simple solution for large area a simple solution for large area UV-RICH detectors UV-RICH detectors R. Chechik, A. Breskin and C. Shalem Dept. of Particle Physics, The Weizmann Institute of Science, 76100 Rehovot, Israel
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Transcript of C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________...
11C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Thick GEM-like multipliers: Thick GEM-like multipliers: a simple solution for large area a simple solution for large area
UV-RICH detectorsUV-RICH detectors
R. Chechik, A. Breskin and C. Shalem
Dept. of Particle Physics, The Weizmann Institute of Science, 76100 Rehovot, Israel
22C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
30 years of “Hole-multiplication” history:30 years of “Hole-multiplication” history:
•Breskin, Charpak NIM108(1973)427 discharge in glass capillaries
•Lum et al. IEEE NS27(1980)157, Del Guerra et al. NIMA257(1987)609 Avalanches in holes
•Bartol, Lemonnier et al. J.Phys.III France 6(1996)337 CAT
•Sakurai et al. NIMA374(1996)341, Peskov et al. NIMA433(1999)492 Glass Capillary Plates
•Sauli NIMA386(1997)531 GEMGEM
•Ostling, Peskov et al, IEEE NS50(2003)809 G-10 “Capillary plates”
33C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Expanding the standard GEM…Expanding the standard GEM…
• 1-2 holes/mm2
• PCB tech. of etching + drilling • Simple and robust Simple and robust • Sub-mm to mm spatial
resolution• VTGEM~2KV (at atm. pressure)• 101055 gain in single-TGEM, 101077 gain in double-TGEM • Fast (few ns) • Low pressure (<1 Torr(<1 Torr) gain 10104 4
• 50 holes/mm2
• Microlithography + etching• High Spatial resolution (tens of microns) • VGEM~400V• >10>1033 gain in single GEM• 10106 6 gain in cascaded GEMs• Fast (ns)• Low pressure – gain~30
1mm
TGEMStandard GEMGeometry:
similar to “Optimized
GEM” [Peskov]
But: etched rim
44C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Expanding the standard GEM Expanding the standard GEM ??
What scales up? •The GEM geometry
and what does not?
•Electric fields•Electron diffusion•Electron transport•Gain•Timing properties•Rate capability•Ions transport
-> it is a new device that has to be studied from scratch !
55C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
The TGEMs:The TGEMs:
A TGEM costs ~4$ /unit. With minimum order of 400$ ~120 TGEMs.>10 times cheaper than standard GEM from CERN.
66C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Various TGEMs studied at WISVarious TGEMs studied at WIS
Manufactured by standard PCB techniques of precise drilling drilling in G-10 (+ other materials) and Cu etchingCu etching.
Typical Atm.pressure geometry Low pressure geometryHole
diameter d=0.3mm
Distance between holes a=0.7mm
Thickness t=0.4mm
Hole diameter d=1mm
Distance between holes a=1.5mm
Thickness t=1.6mm
0.1mm rim to prevent discharges
Important for high gains!
0.1mm
Cu G-10
3cm
77C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Electric field Electric field && e e-- transport calculations: transport calculations: Maxwell / GarfieldMaxwell / Garfield
E~4 (KV/cm)
E~25 (KV/cm)
Operated at VTGEM~2KV
•Field values on electrode surfaces•Field value inside the holes•Field direction->focusing into the holes•Dependence on the hole parameters
-1.0 -0.5 0.0 0.5 1.00
5
10
15
20
25
30Electric field along the hole center
E [
kv/c
m]
Z [mm]
multiplication
Hole length
88C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Operation principleOperation principle
Edrift
ETGEM
Etrans
Garfield simulation of electron multiplication in Ar/CO2 (70:30)
Multiplication inside holes -> reduces secondary effects
Each hole acts as an individual multiplier
99C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
TGEM as a Photon detectorTGEM as a Photon detectorConsiderations:1. High field on the pc surface, to minimize back
scattering.2. Good e- focusing into the holes, to maximize effective
QE.3. Low sensitivity for ionizing background radiation. Solution: a reflective pc on top of the TGEM.
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.60.0
0.5
1.0
1.5
2.0
0
Gain~103
1 Atm. Ar/CH4(95:5)
40
20
80
60
100
e- tra
nsf
er
effic
iency
[%
]
Edrift [kv/cm]Slightly reversed Edrift (~50V/cm)
• good photoelectron collection!• Low sensitivity to MIPS
1010C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
For typical operation voltages: Surface field > 5kV/cm • Full photoelectron extraction • High effective QE
TGEM as a Photon detector (‘cont)TGEM as a Photon detector (‘cont)
• TGEMs studied so far are more optically transparent than standard GEM. • Cu: 40-50% area
0.4mm thick0.3mm holes0.7mm pitch
1111C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
EffectiveEffective gain and gain and effectiveeffective QE QE
measured gain in current mode is an effective gaineffective gain::
Effective gain = true gain in X efficiency to focus the holes the e- into the holes.
QE in the detector is an effective QEeffective QE:
Eff. QE = true QE X efficiency to X efficiency to of the pc extract the ph.e. detect the ph.e.
i
PCGEM
Reflective pc
i
PC
GEM
Semitransparent pc
1212C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Gain 104-105
Single-photon detection no photon feedback Rise time < 10ns
10ns
Example: TGEM with reflective CsI photocathode(Similar results with semitransparent pc)
Single-TGEM: GainSingle-TGEM: Gain
105
1313C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Higher total gain (106-107) >103 higher gain at same VTGEM
Better stability
Double-TGEM: GainDouble-TGEM: Gain
5 mmEtrans=
3kv/cm
e-
Important for double TGEM: • high Etrans
• Large transfer gap
107
Example: TGEM with a semitransparent CsI photocathode(similar results with reflective pc)
1414C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Problem:•Requires high TGEM voltage.•Damage due to sparks is fatal: after a spark the TGEM deteriorates continuously. (We suspect effects of etching to the SiO2 fibers).• Fatal spark damage was also observed in standard GEMs operating in CF4, due to the high operating voltages.
Solutions:•Segment the TGEM•Cascade several TGEMs.•Test other materials: Kevlar, Teflon, etc.
Operation in CFOperation in CF44
R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
1515C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Electron transfer efficiency Electron transfer efficiency TGEM with a reflective pc (Edrift=0)
e affects energy resolution, detection efficiency, effective QE
Compared to standard GEM, very high fields are reached at the TGEM surface already at low VTGEM . Good e- extraction in all gases.
F
f
Tra
nsf
er
effi
ciency
0.4mm thick0.3mm holes0.7mm pitch
1616C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Electron transfer efficiency Electron transfer efficiency
TGEM with a semitransparent pc is important also for double TGEM operation
(more complex measurement)•Double-sided pc•Double normalization•Single e- pulse counting as before
Full efficiency already at low gains gains 10-100 !
0.4mm thick0.3mm holes0.7mm pitch
1717C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Electron transfer efficiency Electron transfer efficiency -cont’ -cont’TGEM with a semitransparent pc - dependence on Edrift/VTGEM
ETGEM/Edrfit > 1
e- focused to hole
ETGEM/Edrfit < 1
e- collected on GEM top
With typical TGEM operation voltage:
full eff. up to Edrift = 4kv/cm
0.4mm thick0.3mm holes0.7mm pitch
1818C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Energy resolution: 6 keV x-raysEnergy resolution: 6 keV x-rays
FWHM=~20%
E resolution similar to standard GEM
6 keV x-rays
1919C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Counting rate capabilityCounting rate capability
Reflective CsI pc UV photons (185nm)
Total current limit 4*10-7 [Amp/mm2]
0.4mm thick0.3mm holes0.7mm pitch
2020C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Ion back flowIon back flow Affects pc longevity and secondary effects
TGEM with a semitransparent pc
s.t. pc
Start amplification
IBF = ipc/iTGEM
12%
With high VTGEM most of the ions are collected on the top of the TGEM.
0.4mm thick0.3mm holes0.7mm pitch
2121C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Ion back flowIon back flowAffects pc longevity and secondary effects
TGEM with a reflective pc
Reflective pc
IBF = ipc/iTGEM
1400 1500 1600 1700 1800 1900
0.0
0.2
0.4
0.6
0.8
1.0
1.2
98%
Edrift = 0
Ar/CO2(70:30) 760 Torr
10410310 Gain
No
rmal
ized
Io
n B
ack
flo
w
VTGEM (v)
Ion back flow to TGEM top Ion Back flow to upper Mesh
With a reflective photocathode, most of the ions are collected on the top of the TGEM (like in a GEM).
2222C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
SummarySummary
1. G-10 TGEMs tested with several gases.
2. Gains: 105 with a single TGEM; 107 with cascaded double TGEM
3. Fast signals: r.t. <10 ns.
4. The e- transfer efficiency (into the holes) is well understood.
5. Counting rate capability: ~ 106 avalnches/sec x mm2 @ gain 4x104
6. Ion backflow: study in course
7. In TPC-like conditions: IBF with a single TGEM is 12%.
In GPM/reflective pc: IBF with a single TGEM is 98%.
A cascade + other “tricks” (see GEM/MHSP) should reduce IBF .
8. TGEMs of different materials (e.g. Kevlar, Teflon…) for CF4 ?.
9. Will study TGEM of lower optical transparency (higher eff. QE)
2323C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
The endThe end
2424C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
TGEM: Low pressure TGEM: Low pressure operationoperation
0 400 800 1200 160010-3
10-1
101
103
105
107
low pressure isobutane
20 Torr
50 Torr
10 Torr
5 Torr
1 Torr
effe
ctiv
e G
ain
VTGEM
[v]
Single TGEM
10 Torr IsobutaneGain~105; Rise time~5ns
low pressure isobutane
semi-transparent CsI photocathode
2525C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
TGEM: Low pressure TGEM: Low pressure operationoperation
0 1000 2000 3000 4000 500010-2
100
102
104
106
108
.
.doublesingle
doublesingle double
single
0.5 Torr
1 Torr.
10 Torr
low pressure Isobutane2.2mm thickness TGEM
Effe
ctiv
e G
ain
E [V/cm]
low pressure isobutane
semi-transparent CsI photocathode
2626C.Shalem et al, IEEE 2004, Rome, October 18 R. Chechik et al. ________________RICH2004_____________ Playa del Carmen, Mexico
Electron transfer efficiencyElectron transfer efficiencythe efficiency to focus an electron into the TGEM
Pulse counting measurement: •A way to separate the true gain from the effective gain. •Based on single e- pulses• same pc, lamp, gain and electronics, different e- path.• Comparing counting rate provides the fraction of single e events reaching TGEM bottom. (1)
normalization
(2)efficiency
measurment
Example: ref pc
