1/18 01/26/2007mpgd workshop in saga (yorito yamaguchi, cns, univ. of tokyo) 東大 cns における...
TRANSCRIPT
01/26/2007
1/18
MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
東大 CNSにおける GEMの基本動作特性の研究Measurement of basic properties of GEM at CNS, Univ. of Tokyo
Yorito Yamaguchi
CNS, Univ. of Tokyo
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
2/18
Outline Outline
•Introduction
•Setup for Measurements
•Basic properties of Standard-GEM
−P/T dependence, Gain Stability, VGEM dependence
•Development of 150m-GEM
−Feature of 150m-GEM
−Electric field, Gain, Multiplication factor, Gain Stability
•Summary
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Introduction Introduction A new type of GEM was successfully developed using a dry etching technique.
CERN
wetwet etching
Bi-conicalBi-conical
SciEnergy Co., Ltd
drydry etching
CylindricalCylindrical
Etching technique
The cross section of a hole
Hole shape
Basic properties were measured to evaluate the performance of SciEnergy-GEM.
•P/T dependence, Gain Stability ,VGEM dependence.
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Setup for MeasurementsSetup for Measurements
• ED = 0.5kV/cm
• ET = EI
• VT = VI = VGEM
•Moisture % < 10ppm
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Measurement of basic properties−P/T dependence of Gain
−Gain Stability
−VGEM dependence of Gain
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Ar/CO2
Longitudinal axis : Gain
Horizontal axis : P/T [Torr/K]
Range : 2.50~2.65
It was observed that Gain decreases exponentially as P/T increases.
A change of A change of 1%1% in in P/T value causes a P/T value causes a gain variation of gain variation of 9%9% (Ar/CH(Ar/CH44) and of ) and of 11%11%
(Ar/CO(Ar/CO22).).
P/T Dependence of Gain ①P/T Dependence of Gain ①
Ar/CH4
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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533.2749.3exp
4Ar/CH T
PR
533.2553.4exp
2Ar/CO T
PR
Base point in Gain
•P=760.0Torr
•T=300.0K
→P/T=2.533 [Torr/K]
Both results of SciEnergy-GEM and CERN-GEM are in good agreement with the unique exponential function.
The results with different P/T can be normalized to the same condition using the obtained function.
P/T Dependence of Gain ②P/T Dependence of Gain ②
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Gain Stability ①Gain Stability ①
It was reported that gain of CERN-GEMCERN-GEM increases (or decreases) as a function of illumination time.
A. Orthen et al., NIM A 512 (2003) 476
Known problem in gain stability
1. Due to shape of a GEM hole• Charge up of the insulator surface
inside the hole.2. Due to nature of insulator3. Due to surface conditions
Possible reason Possible reason
Measurement condition
•VGEM is kept constant during the measurement.
•Rate of signals is 3Hz for all measurements.
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Gain Stability ②Gain Stability ②All results are normalized to the condition of P/T=2.533 [Torr/K] using the obtained relation between Gain and P/T.
Gain variation
•SciEnergy-GEM
•within 0.5% (both case)
•CERN-GEM
•Increase 15% (Ar/CH4)
•Increase 45% (Ar/CO2)
Without charge-up
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Gain Stability ③Gain Stability ③SciEnergy-GEM has a much better gain stability than CERN-GEM.
10m from hole edge
SciEnergy-GEMCERN-GEM
The electric field near the hole edge is distorted due to a bulge of a insulator for CERN-GEM.
→Probability of charging-up is higher for CERN-GEM than SciEnergy-GEM.
Drift direction of electron
E [V/cm]
Electric field inside a GEM hole
VGEM=350V
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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VVGEMGEM Dependence of Gain Dependence of GainSciEnergy-GEM can attain 20% (Ar/CH4) and 50% (Ar/CO2) higher gain than CERN-GEM at the same VGEM.
→SciEnergy-GEM has larger effective area in multiplication than CERN-GEM.
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Development of 150m-GEM−Feature of 150m-GEM
−Electric field of 150m-GEM
−Gain of 150m-GEM
−Multiplication factor
−Gain Stability
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Feature of 150Feature of 150m-GEMm-GEMThe dry etching technique can allow to fabricate a thicker GEM (Thick-GEM) than Standard-GEM (insulator thickness:50m).−150m-GEM is comparable to a triple layer structure of Standard-GEM with respect to the total length of a hole.
•Larger effective path length for multiplication
•Less effect of transmission efficiency
Advantage of 150m-GEM 150150m-GEM is expected m-GEM is expected to multiply electrons to multiply electrons more effectively than more effectively than triple layer structure of triple layer structure of Standard-GEM.Standard-GEM.
150m
70m
140m
• Cu(8m) + LCP(150m) + Cu(8m)
• = 70m
• hole pitch = 140m
Structure of 150m-GEM
*LCP:Liquid Crystal Polymer
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Electric Field of 150Electric Field of 150m-GEMm-GEMVGEM/50m=250V/50m
>0
The electric field of Thick-GEM is much stronger than that of Standard-GEM.
→Especially, 150m-GEM reaches plateau for about 50m.150150m-GEM should have a better multiplication ability m-GEM should have a better multiplication ability
than Standard-GEM.than Standard-GEM.
● 150m-GEM VGEM=750V
● 100m-GEM VGEM=500V
● Standard-GEM (50m) VGEM=250V
Electric field through the hole center
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Gain of 150Gain of 150m-GEM m-GEM
Standard-GEM
100m-GEM
150m-GEM
Gainat 300V/50m
Magnification Ratio
3.9 x104
1.0 x103
30
3.6 x102
1.3 x103
1.0
→(Gain100m-GEM)3/2
Tamagawa-san’s result
•150m-GEM had a continuous discharge at 270V/50m.(Gain~4000)
150150m-GEM can attain much higher Gain than m-GEM can attain much higher Gain than Standard-GEM at the same VStandard-GEM at the same VGEMGEM/50/50m.m.
Gain for Standard-GEM is obtained by triple GEM structure.
Ar(70%)/CO2(30%)
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Multiplication FactorMultiplication Factor
layers ofNumber :
efficiencyon Transmissi:
factortion Multiplica:
/1
n
M
GainMMGain
T
T
nn
T
Simulation results of the transmission efficiency is used.
■150m-GEM (M150):T150=0.17
■100m-GEM (M1003/2):T100=0.34
■Standard-GEM (M503):T50=0.24
As expected from the electric field inside a hole, 150As expected from the electric field inside a hole, 150m-GEM m-GEM has the highest multiplication factor.has the highest multiplication factor.
EI is stronger than for Standard-GEM and 150m-GEM.
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Gain Stability of 150Gain Stability of 150m-GEMm-GEM
Ar(90%)/CH4(10%)
•The rate of signals = 2.5Hz
•VGEM=230V
Gain of 150Gain of 150m-GEM is stable within 1.0% for 9 hours.m-GEM is stable within 1.0% for 9 hours.→150150m-GEM has a good gain stability as well as m-GEM has a good gain stability as well as Standard-GEMStandard-GEM
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SummarySummary•The basic properties have been measured to evaluate the performance of SciEnergy-GEM.
−Gain decreases exponentially as P/T increases.
•A change of 1% in P/T value causes a gain variation of 9% (Ar/CH4) and of 11% (Ar/CO2).
−SciEnergy-GEM has a much better gain stability than CERN-GEM.
•Probability of charging-up is higher for CERN-GEM because of a distortion of electric field near the hole edge.
−SciEnergy-GEM can attain higher gain than CERN-GEM at the same VGEM.
•150m-GEM has been fabricated successfully using dry etching.
−Electric field of 150m-GEM is much stronger than that of Standard-GEM.
−150m-GEM has much higher gain and multiplication ability with a good gain
stability than a triple layer structure of Standard-GEM.
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Back up
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Applications Applications We are developing some detectors using GEMs.
•GEM-TPC
→S.X. Oda et al., NIM A 566 (2006) 312
•Photon detector
•Hadron Blind Detector (HBD) installed in PHENIX@RHIC.
→Please hear Ozawa-san’s talk (15:15~ in tomorrow session).
•Neutron Counter
→Development is now on going.
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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),(),(1
ion
ET
P
T
P
R
NENN A
dxx
T
P
T
P
R
NdxxGain A ),(exp)(exp
From the equation of state,
T
P
R
NN A
eTemperatur:
Pressure:
constant Gas:
ionizationfor section Cross:
number sAvogadro':
densitynumber Particle:
ionizationfor path freeMean :
tcoefficien TownsendFirst :
ion
T
P
R
N
N
A
The expected relation between Gain and P/T should be exponential.
Relation between Gain and P/TRelation between Gain and P/T
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Simulation of GEM structure
Aim of study
•To understand the behavior of electrons inside a GEM hole qualitatively and quantitatively.
•To search for optimum GEM structure.
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Potential Distribution of GEM holePotential Distribution of GEM holeThe electric field inside the GEM hole was calculated using Maxwell 3D.
Potential distributions are very similar in both cases.
The calculation was carried out for two type of GEM.
•Bi-conical (CERN-like)
•Cylindrical (SciEnergy-like)
VGEM=350V
Bi-conical Cylindrical
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Electric Field inside GEM holeElectric Field inside GEM holeHole center 10m from hole edge
Drift direction of electron
Although there is little difference between them at hole Although there is little difference between them at hole center, the electric field of Bi-conical near the hole edge is center, the electric field of Bi-conical near the hole edge is distorted due to a bulge of a insulator.distorted due to a bulge of a insulator.
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Simulation of AvalancheSimulation of AvalancheThe avalanche inside a GEM hole was simulated using Garfield.
•The calculation results from Maxwell 3D are the inputs to Garfield.
•Avalanche simulation ware carried out with two methods.
•True path integration
•Projected path integration
•Ar/CO2 (70:30) was used at P=760.0Torr, T=300.0K.
ions
electrons
Gain can be defined as a following equation.
layers ofNumber :
efficiencyon Transmissi:
factortion Multiplica:
n
M
MGain
T
nT
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Behavior of ElectronsBehavior of ElectronsCreated point of electron Number of created electron Lost point of electron
GEM
•There is a significant difference in multiplication near the hole edge.
•SciEnergy-GEM has better multiplication ability than CERN-GEM.
•More than 70% of secondary electrons are absorbed by the lower electrode of GEM.
Gain
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Gain Gain
Simulation results are qualitatively consistent with measured result, but they are quantitatively inconsistent.
3
1
triplesingle GainGain
It is needed to improve the calculation method It is needed to improve the calculation method in multiplication inside a GEM hole.in multiplication inside a GEM hole.
Most of electrons created near the hole edge are absorbed by electrode.
→There is not a big difference in gain as seen in multiplication factor.
01/26/2007 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)
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Setup for Measurements of 150Setup for Measurements of 150m-GEMm-GEM
• ED = 0.5kV/cm
• VI = VGEM/3
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Gain of 150Gain of 150m-GEM (Ar/CHm-GEM (Ar/CH44))