takeshi fujiwara, hiroyuki takahashi, kaoru fujita, naoko iyomoto department of nuclear engineering...
TRANSCRIPT
Takeshi Fujiwara, Hiroyuki Takahashi, Kaoru Fujita, Naoko Iyomoto
Department of Nuclear Engineering and Management, The University of Tokyo, JAPAN
Study on transparent electrode ITO-MSGC for Gas Proportional Scintillation Counter
MPGD’09 June 13th 2009@Crete, Greece
Outline
Introduction Multi-Grid MSGC (M-MSGC) Active scintillation method Fabrication of transparent M-MSGC (ITO) Test results in X-ray Summary
1. Introduction
J-PARC (Japan Proton Accelerator Research Complex)
400MeV Lineac
Mercury target
3GeV synchrotron
MLF
MLF (Material and Life Facility)MLF (Material and Life Facility)Facility for material analysis and life scienceFacility for material analysis and life science
Overview
MLF spectrometers
And more is being developed
MLF spectrometers
A facility to analysis materials with reflection of neutrons
MirrorTarget
Dete
ctor
Neutron beam (Various wave length)
Diffraction
Diagrammatic sketch of RefelctrometerDiagrammatic sketch of Refelctrometer
Θ
2. Multi-Grid MSGC (M-MSGC)
Anode
Cathode• Micro-strip electrodes patterned on glass plate• <100µm between anode & cathode• Up to 1600V between each strips• Electron is multiplied with avalanche and produces charge• Charge division readout method for 1D position detection• 2D position detection by layering 2 plates
Diagrammatic sketch MSGC (Micro Strip Gas Counter)
Avalanche
Electron
• Charge up causes decrease of gas gain• Damage caused by sudden discharge• Bad in stability
• High count rate• Low cost• Could be used with high pressure gas
MSGC (Micro Strip Gas Counter)
Good
BadAnode Cathode
Anode Cathode...
Separation of two strong electric fields
Small surface charge Low surface resistance
Grid1 Grid2
Multi-grid-type MSGC (M-MSGC)
Avoid charge-up and sudden discharge
Vanode > Vgrid1 > Vgrid2 > Vcathode
AG1
G2G3
G4 C
4 cm x 4 cm active areaAnode width: 5 µm4 grids(20,25,35,42.5µm) and 10 µm gaps
400m
A test plate consists of 4 grids + anode + cathode
Obtained energy resolution was 14.6% FWHM.(Gas gain =3000)
6keV
Ar escape
Pulse Height Spectrum for 6keV X-rays
Experiment is done with 6keV X-ray (@KEK Photon Factory)
0.1mmϕ beam, 400cps/mm2
Ar(30) + CH4(70%) ＠１ atm
Neutron Image by Floating Pad Charge Division Method6mm
6mm
1mm
Spatial resolution 0.6mm FWHM
3. Active scintillation
Active scintillator method (proposed in MILAND)
Incident neutron
MSGC
Photo Multiplier
Electron drift
Primary light
Position Measurement at T=Gap/Vdrift
d
Primary light signal enables to calculate the depth of interaction information, and reduce parallax error
Tcharge signal
Tprimary light
Problems of conventional method
Photo Multiplier
Unwanted diffraction
Incident neutron
Stop
Primary light
MSGC
Incident neutron
Since neutrons have to go through the MSGC, unwanted diffractions and stops can be caused.
Problems of conventional method
Photo Multiplier
MSGC
Incident neutron
In order to avoid unwanted diffraction or stop, MSGC should be under the conversion area. However, since ordinary MSGC’s are not transparent, primary light cannot get to PMT.
Primary light
Electron drift
Problems of conventional method
Photo Multiplier
MSGC
Incident neutron
But if the MSGC is transparent…,
Primary light
Electron drift
Problems of conventional method
Photo Multiplier
MSGC
Incident neutron
Primary light
Electron drift
But if the MSGC is transparent…, primary light signal enables to calculate the depth of interaction information, and reduce parallax error without worrying about the unwanted diffraction
d
4. ITO - The transparent MSGC
ITO MSGC
ITO(Indium Tin Oxide) is known as a transparent conductive material used for LCD display.
Optical transmission is 80-90%. We fabricated a multi-grid-type MSGC
using ITO. OA10 glass substrate 170nm thick ITO layer Use with Ar/CF4 gas for efficient GSPC
This is ITO MSGC
If you have super excellent eyes, may be you can see…
Picture of ITO MSGC
ITO version of M-MSGC Electrode pattern is same as our conventional M-MSGC
Transmissivity of ITO
5. Test results with X-rays
Experimental SetupAr(70%) + CH4(30%) ＠１ atm
HV(2ch out put)ORTEC 456
TektronixDPO 4034
Oscilloscope
- 800V
PMTHamamatsu
R5600U
55Fe
3mm
PMT or ANODE
Pocket MCA8000A
PC
Chamber inside
Cathode Anode
ORTEC 570
HV (4ch out put)ORTEC 710
Socket
E5780
PMT R5600USensitive Area300nm ～ 650nm
Anode
Cathode
Grid 1
Grid 2
Active area2.7 cm
3.0cm
8.0mm
Optical Signal
Charge Signal
Test of operation as a proportional counter
ANODE signal
CATHODE signal
Ar 70% + CH4 30%
LIGHT
CHARGE
100ns
Obtained energy spectra
ITO M-MSGC
FWHM25.4%
FWHM27.4%
Charge Light
ANODE HV
AM
PLI
TU
DE
Gas gain & PMT Spectra
5.2. Position Scan with 6keV X-ray beam
Test of position readoutExperimental setup
HV(2ch out put)ORTEC 456
TektronixDPO 4034
Oscilloscope
- 1100V
HamamatsuR2486-02
PSPMT
3mm
PMT or ANODE
MPA
PC
Chamber inside
Cathode Anode
ORTEC 570
HV (4ch out put)ORTEC 710
PS PMT R-2486Sensitive wave length300nm ～ 650nm
Ar(90%) + CF4(10%) ＠１ atm
Position ReadoutORTEC 464
6keV X-ray
Optical Signal
Charge Signal
Position measurement
Hamamatsu R2486-02 PSPMT
ITO-MSGC
X1
X2
Y2
Y1
Ar/CF4 90:10
PS M
odule
ORTEC 464
Schematic of Hamamatsu PS-PMT R-2486-2
5mm Position scanned result obtained with PSPMT
Channel
6keV collimated X-ray beam (scanned in 25mm * 25mm area)
Cou
nt
5mm5mm
≈2.5mm(FWHM)≈2.5mm(FWHM)
Experiment is done with 6keV X-ray (@KEK Photon Factory)
0.1mmϕ beam, 400cps/mm2
Hamamatsu PS-PMT R-2486-2 + Ortec 464 Position Detection module
Results of position scan by 5mm
5mm
5mm
Y A
xis
(Pea
k ch
anne
l)
X Axis (Peak channel)
Experiment is done with 6keV X-ray (@KEK Photon Factory)
0.1mmϕ beam, 400cps/mm2
Hamamatsu PS-PMT R-2486-2 + Ortec 464 Position Detection module
Future work
ITO-MSGC SiPM array
ITO-MSGCCharge signal (Y) Normal PMT
Light signal (X)
Optical mask(position modulation)
He3 + CF4 He3 + CF4
Use both of charge/optical signal for position detection
Transmissivity
Future work
He3 + CF4
Anger camera
ITO-MSGC
PMT
Summary
ITO M-MSGC has been fabricated and tested with 6keV X-rays.
Position sensing by optical signal has been demonstrated.
Active scintillation could be a solution for higher spatial resolution
Optics for better light collection should be considered.
2D Multi-Grid-Type MSGC by induced charge sensing Place FLOATING pads close to cathode Positive Ions stay on pads Pad charge can be read out through
substrateA G Pad C
ReadoutStrips
Charge stay on pads
Avalancheregion