a new design of mpgd: micro-mesh micro pixel chamber (m 3 -pic)
DESCRIPTION
A new design of MPGD: Micro-Mesh Micro Pixel Chamber (M 3 -PIC). A.Ochi *, Y.Homma , T.Dohmae , H.Kanoh , T.Keika , S.Kobayashi , Y.Kojima , S.Matsuda , K.Moriya , A.Tanabe , K.Yoshida Kobe University. Introduction. Introduction to m -PIC Design of new M 3 -PIC - PowerPoint PPT PresentationTRANSCRIPT
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A new design of MPGD:Micro-Mesh Micro Pixel Chamber
(M3-PIC)
A.Ochi*, Y.Homma, T.Dohmae, H.Kanoh, T.Keika, S.Kobayashi, Y.Kojima, S.Matsuda, K.Moriya, A.Tanabe,
K.YoshidaKobe University
2nd RD51 Paris 14th Octber 2008
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Introduction
2nd RD51 Paris 14th Octber 2008
Introduction to m-PIC Design of new M3-PIC Advantages using micro mesh
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Introduction to m-PICM3-PIC is based on m-PIC
m-PIC : micro pixel gas chamberLarge area with PCB tech.pitch :400μmhigh gas gainsmall discharge damage
4%
150001700(with capillary)
Maximumgain
~35%uniformity ( σ)
400μm(300μm possible)
200μmPitch
30×30cm210×10cm2Area>30 daysLong time 70001000Stable Gain
m-PICMSGC
Invented by A.Ochi and T.Tanimori ( NIMA 471 (2001) 264) Application: X-ray imaging, Gamma camera, Medical RI tracing, etc.
2nd RD51 Paris 14th Octber 2008
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Gaseous TPCwith micro-electrodes
Scintillation Camera
Recoil Electron : 3D Sequential Track ->Direction, Energy
Less cost than semiconductorScattered Gamma-ray : Energy, Direction
Tanimori, et al, 2004
α
Introduction to m-PIC (cont’d) Applications --- Micro TPC Gamma ray camera
(ETCC: Electron-Tracking Compton Camera)
3 D Track
X, Y from m-PIC+Z from timing
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Design of M3-PIC Micro pixel chamber (m-PIC) + With micro mesh
Higher gain in stable operation (~5x104)
Low ion backflow (<1%)
400mm
100mm70mm230mm
165mm
AnodeCathode
Support wire
Micro Mesh
1cmDrift/detection area(Filled by gas)
Drift plane
2nd RD51 Paris 14th Octber 2008
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Higher gas gain will be attained safely (104-5) High electric field is
formed larger area around the anode
Without increase of e-field near cathode edge Electron emission from
cathode edge is reduced Streamer from anode is
quenched
Reduction of positive ion backflow m-PIC: ~30% M3-PIC: < 1%
Advantages usingmicro mesh
AnodeAnodeSubstrat
e
Mesh
Cathode
AnodeSubstrate
Cathode
E-field strength on m-PIC
E-field strength on M3-PIC
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Setup and operation tests
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Setup Gas gain measurements Ion backflow measurements
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0.5mmMicro scope picturesfor same place(different focus point)
Micro mesh mounted on m-PIC by hand.Size of m-PIC = 3cm x 3cm.
Setup
14th Octber 20082nd RD51 Paris
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Gas gain measurements Gain dependency on
Anode voltage (=Va) Mesh voltage (=Vm) Drift field (=(Vd-Vm)/1cm)
165 mm
100mm
Drift Plane
CathodeAnode Signal
Vd
Va
MeshVm
2nd RD51 Paris 14th Octber 2008
1cm
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Gain dependence of drift field Higher drift field
Lower electron collection efficiency on anode
Gain decrease Energy resolution
worseNo escape peak found
in 2kV/cm Maximum gain
100V/cm < E_d < 500V/cm
E_d below 100V/cm Ion-electron
recombination
E_drift = 300V/cm
E_drift = 1kV/cm
E_drift = 2kV/cm
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Electron drifts toward anode (simulation)
Electrons are absorbed in the mesh or cathodes when electric field in drift region is higer.
E_drift = 300V/cm E_drift = 1kV/cm
anode anodecathode cathode
meshmesh
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Gain dependence on Vm and Va E_drift = 300V/cm Maximum gain : 5 x 104
Va- gain
1000
10000
100000
610 630 650 670 690 710Va(V)
gain
Vm=-300VVm=-200V Vd=Vm-300Vm=-100V
Gap of mesh: 165mmMesh thickness: 5mmGas: Ar:C2H6 = 50:50
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Ion backflow (IBF) Ion backflow: The fraction of total avalanche-generated
ions reaching to drift region. Serious problem for TPC readout
m-PIC (no mesh) M3-PIC
Low IBF
Simulation Simulation
2nd RD51 Paris 14th Octber 2008
Ion drift lines from anodes
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Setup for ion backflow measurements Pico-ammeter is
inserted in Drift and Anode line
IBF = ( I_drift/I_anode)
Wireless data taking for keeping insulation
100mm
Drift Plane
Cathode
Anode
Vd (-100V~-1kV)
Va(~500V)
Mesh (5mm or 20mm) Vm
(-150V~350V)
A
A
Pico ammeter
Pico ammeter
Data collectionby wireless
b (Sr90)
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IBF of M3-PIC IBF dependence on
drift field and mesh thickness
IBF dependence on mesh voltage
Gas: Ar 90% + C2H6 10% Gain = 104 for these tests Liner dependence of IBF on drift field Small IBF for thicker mesh Optimum point of mesh voltage
Minimum IBF = 0.5%2nd RD51 Paris 14th Octber 2008
Vm = -250V E_drift = 100V/cmMesh 20 micron
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Discharge studies for MPGD
2nd RD51 Paris 14th Octber 2008
Carbon dissociated on surface Number of discharges and HV drop
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Carbon dissociated from ethane deposits on polyimide surface
5 sparks 50 sparks 150 sparks
200 sparks300 sparks
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Correlation between number of discharges and voltage drop after the test
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Summary New MPGD design: M3-PIC was developed
Combined with m-PIC and micro mesh Ideal electrical fields are formed around anodes for gas avalanche
Prototype was manufactured and tested Maximum gain of 5 x 104 has been attained at present
A few time larger than the gain of simple m-PIC Minimum IBF of 0.5% has been attained at present
Future Prospects Optimization of structure parameters (mesh gap, mesh
thickness … etc.) and operation parameters (HV, gas etc.) Combination with existence large area m-PIC
Testing imaging and tracking capabilities Long term operation test
2nd RD51 Paris 14th Octber 2008