J-PARCでのハイパー核ガンマ線分光 実験に向けたHyperball-Jの建設状況 東北大理、 KEK、 セイコーEG&G、 富士電機システムズ 白鳥昂太郎、 田村裕和、 小野浩、 笠見勝裕、 小池武志、 竹内孝行、 千賀信幸、 春山富義、 保川幸雄 and the Hyperball-J collaboration Contents Hyperball-J Design Mechanical cooling system Radiation damage R&D Summary 2007 JPS in Hokkaido University 2 Hyperball-J E13 experiment at J-PARC Several light hypernuclear g-ray spectroscopy experiments are planned. (4LHe, 7LLi, 10LB, 11LB, 19LF ) Ge detector×32 70% relative efficiency N-type Transistor reset type LN2 cooling ⇒Mechanical cooling ~6% photo peak efficiency @ 1 MeV from geant4 simulation Hyperball-J (half) 2007 JPS in Hokkaido University 4 Hyperball-J design : “Wall-type” configuration Wall-type Large photo-peak efficiency Compact detector size Low cost of PWO crystal Flexibility Counting rate Target and Inner detector Experimental requirements Hyperball 1st 2007 JPS in Hokkaido University 5 Hyperball-J design : “Wall-type” configuration Wall-type Beam Large photo-peak efficiency Compact detector size Low cost of PWO crystal Flexibility Counting rate Target and Inner detector Experimental requirements Hypernuclear g-ray spectroscopy mode Hyperball-J (half) 2007 JPS in Hokkaido University 6 Hyperball-J design : “Wall-type” configuration Wall-type Beam Large photo-peak efficiency Compact detector size Low cost of PWO crystal Flexibility Counting rate Target and Inner detector Experimental requirements X atom X-ray spectroscopy mode Hyperball-J (half) 2007 JPS in Hokkaido University 7 Hyperball-J design : Frame design Upper view As compact as possible Hyperball-J frame2007 JPS in Hokkaido UniversityDriving parts 8 Mechanical cooler -Suppression for Radiation damage- Requirements on Hyperball-J Beam intensity J-PARC ~10.0 MHz K beam (w/ contamination p) KEK 2.0 MHz p beam Severe radiation damage (~1 month experiment is the limit for KEK) at J-PARC High counting rate Full model change of Hyperball !! Mechanical cooler PWO background suppressor Waveform readout 2007 JPS in Hokkaido University 10 Radiation damage Effect of damage Energy resolution gets worse because the electron-hole pair is trapped by the damage of Ge crystal. ~109 neutron/cm2 : Visible effects @ KEK ~1010 neutorn/cm2 : Terrible effects @ J-PARC The effects can be suppressed by keeping the temperature of Ge crystal below ~85 K. ⇒Mechanical cooling FWHM LN2: >90 K Mechanical cooling : >75 K Energy resolution vs “Ge crystal Temperature” (damaged Ge) FWTM E. Hull and R. H. Pehlet al., IUCF Ann. Rep. 143,2007 (1993) JPS in Hokkaido University 11 Mechanical cooler Requirements ﾊﾞｯﾌｧﾀﾝｸ ｲﾅｰﾀﾝｽﾁｭｰﾌﾞ 提供 富士電機 ﾊﾟﾙｽﾁｭｰﾌﾞ ｶﾞｽﾋﾟｽﾄﾝ 冷却端 Large cooling power Low vibration Compact size Long term stability 蓄冷器 膨張機 ⇒ Pulse tube refrigerator 圧縮機 ﾋﾟｽﾄﾝ 圧縮機 Sterling cooler Pulse tube cooler （Mechanical piston） （Gas piston） 放熱機 蓄冷器 膨脹機 圧縮機 放熱機 蓄冷器 膨脹機 ﾊﾟﾙｽﾁｭｰﾌﾞ ｶﾞｽﾋﾟｽﾄﾝ ｲﾅｰﾀﾝｽﾁｭｰﾌﾞ Conventional Ge detector + Refrigerator ⇒How to achieve ? 2007 JPS inthose Hokkaidorequirements University ﾊﾞｯﾌｧﾀﾝｸ 12 Mechanical cooler 提供 富士電機 Requirements Large cooling power Low vibration Compact size Long term stability ⇒ Pulse tube refrigerator 圧縮機 Phase shifter (Buffer tank, inertance tube) Pressure wave generator (sterling) Sterling cooler Pulse tube coller （Mechanical piston） （Gas piston） 放熱機 蓄冷器 膨脹機 圧縮機 放熱機 蓄冷器 Pulse Tube Regenerator 膨脹機 ﾊﾟﾙｽﾁｭｰﾌﾞ ｶﾞｽﾋﾟｽﾄﾝ ｲﾅｰﾀﾝｽﾁｭｰﾌﾞ Conventional Ge detector + Refrigerator ⇒How to achieve ? 2007 JPS inthose Hokkaidorequirements University ﾊﾞｯﾌｧﾀﾝｸ 13 R&D Ge Three difficulties 1. Electric noise • Insulation 2. Microphonic noise by mechanical vibration • Flexible joint 3. Cooling power • Small heat resistance • Water cooling Straight heat rod Flexible joint Insulation Pulse Tube Temperature of Ge crystal : ~76 K Energy resolution @ 60Co 1.3 MeV : 2.2 keV (FWHM) (2.1 keV @ cooler power off) 2007 JPS in Hokkaido University Water cooling Cold head 14 Tohoku University, May 2007 Ge detector Electric power meter Mechanical cooler power supply DAQ PC Mechanical cooler 2007 JPS in Hokkaido University 15 The first test… LN2 60Co 1.3 MeV Mechanical cooler ~2 keV g-ray energy [keV] 2007 JPS in Hokkaido University >10 keV g-ray energy [keV] 16 Energy resolution : LN2 60Co 2.1 keV Pulser 2007 JPS in Hokkaido University g-ray energy [keV] 17 Energy resolution : Mechanical cooler 60Co 2.2 keV Pulser 2007 JPS in Hokkaido University g-ray energy [keV] 18 Final design The first Ge detector will be delivered in October. Ge Cooler 13 cm ~110 cm In-line mechanical cooler Water-cooling （regenerator, compressor） 2007 JPS in Hokkaido University 19 Summary Hyperball-J Wall-type configuration Position-adjustable frame designed Mechanical cooling Suppression of severe radiation damage at J-PARC Required Ge crystal temperature (<85 K) and energy resolution (~2 keV) achieved The first Ge detector delivery in October 2007 JPS in Hokkaido University 20
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