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MEG 実験用液体 Xe scintillation detector の 40MeV γ 線を用いた性能評価 II

MEG 実験用液体 Xe scintillation detector の 40MeV γ 線を用いた性能評価 II. 東京大学　久松康子. 東大素セ、早大理工総研 B 、阪大理 C 、高エ研 D 、 BINP-Novosibirsk E , INFN-PISA F , PSI G 岩本敏幸、大谷航、小曽根健嗣、菊池順 B 、 久野良孝 C 、澤田龍、鈴木聡 B 、寺沢和洋 B 、道家忠義 B 、西口創、 服部紘二 B 、春山富義 D 、真木晶弘 D 、真下哲郎、三原智、 森俊則、八島純 D 、山口敦史 B 、山下了、

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MEG 実験用液体 Xe scintillation detector の 40MeV γ 線を用いた性能評価 II

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  1. MEG実験用液体Xe scintillation detector の40MeV γ線を用いた性能評価II 東京大学　久松康子 東大素セ、早大理工総研B、阪大理C、高エ研D、 BINP-NovosibirskE, INFN-PISAF, PSIG 岩本敏幸、大谷航、小曽根健嗣、菊池順B、 久野良孝C、澤田龍、鈴木聡B、寺沢和洋B、道家忠義B、西口創、 服部紘二B、春山富義D、真木晶弘D、真下哲郎、三原智、 森俊則、八島純D、山口敦史B、山下了、 山下雅樹B、山田秀衛、吉村浩司D、吉村剛史B、 A.A.GrebenukE, D.GrigorievE I.IoudineE, D.NicoloF, S.RittG, G.SignorelliF 2003年9月12日　日本物理学会秋季大会

  2. The current status and schedule of MEG experiment Outline • Development of MEG Experiment Detectors ＊Gamma beam test @PSI ＊Liq. Xe Calorimeter -Filler study for the Liq. Xe calorimeter ＊COBRA Magnet • Schedule of MEG experiment • Summary 東大素セ、早大理工総研B、阪大理C、高エ研D、 BINP-NovosibirskE, INFN-PISAF, PSIG 久松康子、岩本敏幸、大谷航、小曽根健嗣、菊池順B、 久野良孝C、澤田龍、鈴木聡B、寺沢和洋B、道家忠義B、西口創、 服部紘二B、春山富義D、真木晶弘D、真下哲郎、三原智、 森俊則、八島純D、山口敦史B、山下了、山本明D、槙田康弘D、 山下雅樹B、山田秀衛、吉村浩司D、吉村剛史B、 A.A.GrebenukE, D.GrigorievE I.IoudineE, D.NicoloF, S.RittG, G.SignorelliF

  3. Development of MEG Detectors

  4. Gamma beam test @ PSI ＊π-p→π0 n π0(28MeV/c)→γγ ＊π-p→nγ E(γ)=129MeV Beam test using the monochromatic gamma beam at PSI πE1 beam line. *monochromatic γ beam the Energy Calibration *2γ from the reaction: π0→2γ the absolute timing measurement

  5. kinematics Eγ γ θ γ θ 2 gamma rays emitted back to back in lab. frame: 55 & 84 MeV δEγ/Eγ < 1% θ<5° 5°=87mrad=8.7cm@1m

  6. piE1 beam line @ PSI Beam properties: Max. momentum: 280 [MeV/c] Solid angle 32[msr] Momentum acceptance 7.8% Momentum resolution 0.8 % π-flux: 8 * 105 /sec @ 1.6 mA expected Dipole Magnet Vertical & horizontal slits Graphite target Quadruple Magnet

  7. -- beam T A Experimental Setup NaI counter Timing Counter Veto counter degrader Trigger : coincidence 2 Counters & Timing counter & Liq.Xe target Liq. Xe

  8. Experimental Setup Cont’d Liq. H2 target • Target • NaI • Timing Counter Target cell: 41mm dia. 103mm length 64bars NaI (assembled to form an 8×8array) 63.5×63.5×406 mm3 Position resolution (radial) : σr=4.8 cm @100MeV Installed in front of NaI detector 2plastic scintillators over lapped (5×5cm2) Lead plate (6mm thick)

  9. Prospects • γ beam from π0→2γ will be used to calibrate the Liq. Xe calorimeter in MEG experiment @ piE5, PSI • Resolution required in MEG experiment • Beam Time : Sep. 24th to Dec. 10th

  10. MEG experiment detectors • Liq. Xe calorimeter Design of liq.Xe calorimeter has almost completed. The start of the construction: 2004 Subjects to be solved: Stress, Deformation, Heat Load, Need of filler

  11. Filler study for the Liq.Xe detector Some incident photons lose their energy in Liq.Xe, which fills space between the detector wall and PMTs. To fill the space with materials of long radiation length (“Filler”) will improve the efficiency of this detector. Signal cable Honeycomb (SUS314) vacuum γ PMT Liq.Xe Incident window PMT holder (G10) PMT cover (acrylic)

  12. Filler study Requirement for Filler: Long radiation length Do not contaminate liq.Xe The same expansion coefficient as the glass used in Stem A mixture of Epoxy resin and glass. Filler is attached directly to the PMT.

  13. Cooling Test PMTs with Filler are cooled down to 150K. The temperature of PMT is controlled by Liq.N2, a cold finger (Cu pipe) and a heater. PMT heater

  14. Now studying… The difference between the thermal expansion rate of epoxy resin and of SUS. Stress on the PMT cover

  15. COBRA Magnet Construction finished! Superconducting coil in cryostat. Compensation coil potentiometer Support frame COBRA Magnet: Solenoid magnet for positron spectrometer Gradient field for high rate events

  16. On the axis Final Excitation Test completed. ＊Magnetic field inside the SC was measured. →Good Agreement with the calculation! ＊Fringe field around the photon detector region was measured. →Suppressed by compensation coils. On the axis Really graded!!

  17. The Schedule of MEG experiment Photon detector : Large prototype @PSI background estimation The construction start in 2004. COBRA magnet : Shipping to PSI on Sep. 26th Installation & Engineering runs in piE5 Beam line : Ready by the spring of 2004 Positron tracker : The construction start in 2004. Electronics & DAQ system : Start assembling in 2004. All the detectors will be installed in piE5 beam line by 2005. Engineering runs will start in 2005. MEG experiment starts at the beginning of 2006.

  18. Summary • Beam test using monochromatic gamma beam starts on Oct. 2nd. • The design of the photon detector has almost completed and now studying details. (Filler problems and so on) • The construction of COBRA Magnet has finished. (Good performance! ) • Engineering runs will start in 2005, and MEG experiment at the beginning of 2006.

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