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

2007 JPS in Hokkaido University 2 Contents  Hyperball-J  Design  Mechanical cooling system  Radiation damage  R&D  Summary

Hyperball-J

2007 JPS in Hokkaido University 4 E13 experiment at J-PARC Several light hypernuclear  -ray spectroscopy experiments are planned. ( 4  He, 7  Li, 10  B, 11  B, 19  F ) ~6% photo peak 1 MeV from geant4 simulation Ge detector×32  70% relative efficiency  N-type  Transistor reset type LN 2 cooling ⇒ Mechanical cooling Hyperball-J (half)

2007 JPS in Hokkaido University 5 Hyperball-J design : “ Wall-type ” configuration Wall-type  Large photo-peak efficiency Compact detector size Compact detector size  Low cost of PWO crystal  Flexibility Counting rate Counting rate Target and Inner detector Target and Inner detector Experimental requirements Experimental requirements Hyperball 1st

2007 JPS in Hokkaido University 6 Hyperball-J design : “ Wall-type ” configuration Wall-type  Large photo-peak efficiency Compact detector size Compact detector size  Low cost of PWO crystal  Flexibility Counting rate Counting rate Target and Inner detector Target and Inner detector Experimental requirements Experimental requirements Hypernuclear  -ray spectroscopy mode Beam Hyperball-J (half)

2007 JPS in Hokkaido University 7 Hyperball-J design : “ Wall-type ” configuration  atom X-ray spectroscopy mode Beam Wall-type  Large photo-peak efficiency Compact detector size Compact detector size  Low cost of PWO crystal  Flexibility Counting rate Counting rate Target and Inner detector Target and Inner detector Experimental requirements Experimental requirements Hyperball-J (half)

2007 JPS in Hokkaido University 8 Hyperball-J design : Frame design Hyperball-J frame Upper view Driving parts As compact as possible

Mechanical cooler -Suppression for Radiation damage-

2007 JPS in Hokkaido University 10 Requirements on Hyperball-J Full model change of Hyperball !!  Mechanical cooler  PWO background suppressor  Waveform readout Severe radiation damage (~1 month experiment is the limit for KEK) High counting rate at J-PARC KEK 2.0 MHz  beam J-PARC ~10.0 MHz K beam (w/ contamination  Beam intensity

2007 JPS in Hokkaido University 11 Radiation damage Energy resolution gets worse because the electron-hole pair is trapped by the damage of Ge crystal.  ~10 9 neutron/cm 2 : Visible KEK  ~10 10 neutorn/cm 2 : Terrible J-PARC The effects can be suppressed by keeping the temperature of Ge crystal below ~85 K. ⇒ Mechanical cooling Effect of damage Energy resolution vs “Ge crystal Temperature” (damaged Ge) E. Hull and R. H. Pehlet al., IUCF Ann. Rep. 143, (1993) LN2: >90 K Mechanical cooling : >75 K FWHM FWTM

2007 JPS in Hokkaido University 12 Sterling cooler （ Mechanical piston ） Sterling cooler （ Mechanical piston ） 圧縮機 蓄冷器 膨脹機 放熱機 膨脹機 蓄冷器 ﾊﾟﾙｽﾁｭｰﾌﾞ 放熱機 ｶﾞｽﾋﾟｽﾄﾝ ﾊﾞｯﾌｧﾀﾝｸ ｲﾅｰﾀﾝｽﾁｭｰﾌﾞ 圧縮機 ﾊﾞｯﾌｧﾀﾝｸ ﾊﾟﾙｽﾁｭｰﾌﾞ ｲﾅｰﾀﾝｽﾁｭｰﾌﾞ 圧縮機 ｶﾞｽﾋﾟｽﾄﾝ 膨張機 冷却端 ﾋﾟｽﾄﾝ 蓄冷器 Requirements  Large cooling power  Low vibration  Compact size  Long term stability ⇒ Pulse tube refrigerator Conventional Ge detector + Refrigerator ⇒ How to achieve those requirements ? Pulse tube cooler （ Gas piston ） Pulse tube cooler （ Gas piston ） Mechanical cooler 提供富士電機

2007 JPS in Hokkaido University 13 圧縮機 蓄冷器 膨脹機 放熱機 膨脹機 蓄冷器 ﾊﾟﾙｽﾁｭｰﾌﾞ 放熱機 ｶﾞｽﾋﾟｽﾄﾝ ﾊﾞｯﾌｧﾀﾝｸ ｲﾅｰﾀﾝｽﾁｭｰﾌﾞ 圧縮機 Requirements  Large cooling power  Low vibration  Compact size  Long term stability ⇒ Pulse tube refrigerator Conventional Ge detector + Refrigerator ⇒ How to achieve those requirements ? Pulse tube coller （ Gas piston ） Pulse tube coller （ Gas piston ） Mechanical cooler Sterling cooler （ Mechanical piston ） Sterling cooler （ Mechanical piston ） Phase shifter (Buffer tank, inertance tube) Pressure wave generator (sterling) Regenerator Pulse Tube 提供富士電機

2007 JPS in Hokkaido University 14 R&D Three difficulties 1.Electric noise InsulationInsulation 2.Microphonic noise by mechanical vibration Flexible jointFlexible joint 3.Cooling power Small heat resistanceSmall heat resistance Water coolingWater cooling Temperature of Ge crystal : ~76 K Energy 60 Co 1.3 MeV : 2.2 keV (FWHM) : 2.2 keV (FWHM) (2.1 cooler power off) Ge Pulse Tube Cold head Water cooling Flexible joint Insulation Straight heat rod

2007 JPS in Hokkaido University 15 Tohoku University, May 2007 Ge detector Mechanical cooler DAQ PC Mechanical cooler power supply Electric power meter

2007 JPS in Hokkaido University 16 LN 2 The first test … Mechanical cooler  keV  keV 60 Co 1.3 MeV  -ray energy [keV]

2007 JPS in Hokkaido University 17  -ray energy [keV]  keV Energy resolution : LN 2 60 Co Pulser

2007 JPS in Hokkaido University 18 Energy resolution : Mechanical cooler  keV 60 Co Pulser  -ray energy [keV]

2007 JPS in Hokkaido University 19 In-line mechanical cooler Water-cooling （ regenerator, compressor ） Cooler Ge 13 cm ~110 cm The first Ge detector will be delivered in October. Final design

2007 JPS in Hokkaido University 20 Summary  Hyperball-J Wall-type configuration Wall-type configuration Position-adjustable frame designed Position-adjustable frame designed  Mechanical cooling Suppression of severe radiation damage at J-PARC Suppression of severe radiation damage at J-PARC Required Ge crystal temperature (<85 K) and energy resolution (~2 keV) achieved Required Ge crystal temperature (<85 K) and energy resolution (~2 keV) achieved The first Ge detector delivery in October The first Ge detector delivery in October