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Takeshi Fujiwara, Hiroyuki Takahashi, Kaoru Fujita, Naoko
IyomotoDepartment of Nuclear Engineering and Management, The
University of Tokyo, JAPAN
Study on transparent electrode ITO-MSGC for Gas Proportional
Scintillation CounterMPGD09 June 13th 2009@Crete, Greece
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OutlineIntroductionMulti-Grid MSGC (M-MSGC)Active scintillation
methodFabrication of transparent M-MSGC (ITO)Test results in
X-raySummary
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1. Introduction
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J-PARC (Japan Proton Accelerator Research Complex)400MeV
LineacMercury target3GeV synchrotron MLFMLF (Material and Life
Facility)Facility for material analysis and life
scienceOverview
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MLF spectrometersAnd more is being developed
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MLF spectrometersA facility to analysis materials with
reflection of neutrons
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2. Multi-Grid MSGC (M-MSGC)
- AnodeCathode Micro-strip electrodes patterned on glass
plate
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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)GoodBadAnodeCathode
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AnodeCathode...Separation of two strong electric
fieldsMulti-grid-type MSGC (M-MSGC)Avoid charge-up and sudden
dischargeVanode > Vgrid1 > Vgrid2 > Vcathode
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AG1G2G3G4C400mmA test plate consists of 4 grids + anode +
cathode
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Obtained energy resolution was 14.6% FWHM.(Gas gain =3000)6keVAr
escapePulse Height Spectrum for 6keV X-raysExperiment is done with
6keV X-ray (@KEK Photon Factory)0.1mm beam, 400cps/mm2
Ar(30) + CH4(70%)atm
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Neutron Image by Floating Pad Charge Division
Method6mm6mm1mmSpatial resolution0.6mm FWHM
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3. Active scintillation
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Active scintillator method (proposed in MILAND)Incident
neutronMSGCPhoto MultiplierPosition Measurement at
T=Gap/VdriftPrimary light signal enables to calculate the depth of
interaction information, and reduce parallax error
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Problems of conventional methodPhoto MultiplierUnwanted
diffractionIncident neutronStopPrimary lightMSGCIncident
neutronSince neutrons have to go through the MSGC, unwanted
diffractions and stops can be caused.
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Problems of conventional methodPhoto MultiplierMSGCIncident
neutronIn order to avoid unwanted diffraction or stop, MSGC should
be under the conversion area. However, since ordinary MSGCs are not
transparent, primary light cannot get to PMT.Primary lightElectron
drift
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Problems of conventional methodPhoto MultiplierMSGCIncident
neutronBut if the MSGC is transparent,Primary lightElectron
drift
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Problems of conventional methodPhoto MultiplierMSGCIncident
neutronPrimary lightElectron driftBut 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
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4. ITO - The transparent MSGC
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ITO MSGCITO(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
substrate170nm thick ITO layerUse with Ar/CF4 gas for efficient
GSPC
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This is ITO MSGCIf you have super excellent eyes, may be you can
see
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Picture of ITO MSGCITO version of M-MSGC Electrode pattern is
same as our conventional M-MSGC
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Transmissivity of ITO
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5. Test results with X-rays
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Experimental SetupAr(70%) + CH4(30%)atm
PMTR5600USensitive Area300nm650nmOptical SignalCharge Signal
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Test of operation as a proportional counterANODE signalCATHODE
signalAr 70% + CH4 30%
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LIGHTCHARGE100ns
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Obtained energy spectraITO
M-MSGCFWHM25.4%FWHM27.4%ChargeLight
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ANODE HVAMPLITUDEGas gain & PMT Spectra
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5.2. Position Scan with 6keV X-ray beam
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Test of position readoutExperimental setupPS PMT R-2486Sensitive
wave length300nm650nmAr(90%) + CF4(10%)atm
Position ReadoutORTEC 4646keV X-rayOptical SignalCharge
Signal
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Position measurementHamamatsu R2486-02 PSPMT
ITO-MSGCX1X2Y2Y1Ar/CF4 90:10ORTEC 464
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Schematic of Hamamatsu PS-PMT R-2486-2
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5mm Position scanned result obtained with PSPMTChannel6keV
collimated X-ray beam (scanned in 25mm * 25mm
area)Count5mm2.5mm(FWHM)Experiment is done with 6keV X-ray (@KEK
Photon Factory)0.1mm beam, 400cps/mm2Hamamatsu PS-PMT R-2486-2 +
Ortec 464 Position Detection module
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Results of position scan by 5mm5mm5mmY Axis (Peak channel)X Axis
(Peak channel)Experiment is done with 6keV X-ray (@KEK Photon
Factory)0.1mm beam, 400cps/mm2Hamamatsu PS-PMT R-2486-2 + Ortec 464
Position Detection module
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Future workITO-MSGCSiPM arrayITO-MSGCCharge signal (Y)Normal
PMTLight signal (X)Optical mask(position modulation)He3 + CF4He3 +
CF4Use both of charge/optical signal for position detection
Transmissivity
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Future workHe3 + CF4 Anger cameraITO-MSGCPMT
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SummaryITO 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 resolutionOptics for better light collection should be
considered.
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Thank youTakeshi [email protected]
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2D Multi-Grid-Type MSGC by induced charge sensingPlace FLOATING
pads close to cathodePositive Ions stay on padsPad charge can be
read out through substrate
Material and life faciity*The place where neutron conversion can
be measured by sensing the primary light and count the time of the
electron drift.****