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

OutlineIntroductionMulti-Grid MSGC (M-MSGC)Active scintillation methodFabrication of transparent M-MSGC (ITO)Test results in X-raySummary

1. Introduction

J-PARC (Japan Proton Accelerator Research Complex)400MeV LineacMercury target3GeV synchrotron MLFMLF (Material and Life Facility)Facility for material analysis and life scienceOverview

MLF spectrometersAnd more is being developed

MLF spectrometersA facility to analysis materials with reflection of neutrons

2. Multi-Grid MSGC (M-MSGC)

AnodeCathode Micro-strip electrodes patterned on glass plate

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

AnodeCathode...Separation of two strong electric fieldsMulti-grid-type MSGC (M-MSGC)Avoid charge-up and sudden dischargeVanode > Vgrid1 > Vgrid2 > Vcathode

AG1G2G3G4C400mmA test plate consists of 4 grids + anode + cathode

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

Neutron Image by Floating Pad Charge Division Method6mm6mm1mmSpatial resolution0.6mm FWHM

3. Active scintillation

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

Problems of conventional methodPhoto MultiplierUnwanted diffractionIncident neutronStopPrimary lightMSGCIncident neutronSince neutrons have to go through the MSGC, unwanted diffractions and stops can be caused.

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

Problems of conventional methodPhoto MultiplierMSGCIncident neutronBut if the MSGC is transparent,Primary lightElectron drift

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

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4. ITO - The transparent MSGC

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

This is ITO MSGCIf you have super excellent eyes, may be you can see

Picture of ITO MSGCITO 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%)atm

PMTR5600USensitive Area300nm650nmOptical SignalCharge Signal

Test of operation as a proportional counterANODE signalCATHODE signalAr 70% + CH4 30%

LIGHTCHARGE100ns

Obtained energy spectraITO M-MSGCFWHM25.4%FWHM27.4%ChargeLight

ANODE HVAMPLITUDEGas gain & PMT Spectra

5.2. Position Scan with 6keV X-ray beam

Test of position readoutExperimental setupPS PMT R-2486Sensitive wave length300nm650nmAr(90%) + CF4(10%)atm

Position ReadoutORTEC 4646keV X-rayOptical SignalCharge Signal

Position measurementHamamatsu R2486-02 PSPMT

ITO-MSGCX1X2Y2Y1Ar/CF4 90:10ORTEC 464

Schematic of Hamamatsu PS-PMT R-2486-2

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

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

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

Future workHe3 + CF4 Anger cameraITO-MSGCPMT

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.

Thank youTakeshi Fujiwarafujiwara@n.t.u-tokyo.ac.jp

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.****