J-PARC ハイパー核実験での ビーム Tracking Detector 高橋俊行（ KEK ） J-PARC 施設の概要 実験方法 考えうる検出器 0.5mm spacing MWPC Silicon Strip Detector まとめ

J-PARC Facility Linac (350m) 3 GeV Synchrotron (25 Hz, 1MW) 50 GeV Synchrotron (0.75 MW) Neutrino to Kamiokande Nuclear and Particle Experimental Facility (HD-Hall) Materials and Life Science Experimental Facility Nuclear Transmutation J-PARC = Japan Proton Accelerator Research Complex

Phase 1 & Phase 2 30 GeV – 9  A 50 GeV – 15  A

1 K1.8 K1.8BR K1.1/0.8 T1 Primary Beam 30GeV-9  A (180MeV LINAC) 30GeV-15  A (400MeV LINAC) flat-top 0.7sec duration 3.64sec Phase2 50GeV-15  A flat-top 0.7sec duration 3.52sec

Experimental Method Beam Spectrometer Target Scattered Particle Spectrometer Decay Particle Detectors (Opt.) Measure trajectories, mom. of beam & scattered particles event by event. Missing Mass (Hypernulcear states) tracking detectors Single Reaction Spectroscopy Coincidense with DPD tagging hypernuclear states Position resolution 200  m – 1mm Secondary Beam , K (K ,K + )  -hypernuclei (K ,  )  -hypernuclei

Beam Intensity (30GeV-9  A) K1.8K1.8BRK1.1/0.8 Max. Mom. [GeV/c] K  Intensity [ppp] 1.8 GeV/c 1.1 GeV/c 0.8 GeV/c 2.0x x x x x x10 5 K/K/ 2.6 (1.8GeV/c)12 (1.1GeV/c)4.7 (1.1GeV/c) Beam Rate [/sec]4.6x x x10 6

PS-K6 Beam Chamber 5mm spacing DC 2.4mm between anode wires and cathode planes Ar:iso-C 4 H 10 = 80:20 2.5mm drift length <100ns drift time Single-hit TDC  ~250  m K6 beam 3.3x10 6 [  /pulse] 1.7sec flat top ~2.0x10 6 [/sec] J-PARC Phase1 では、充分使える。 Multi-hit TDC upgrade of pre-amp. & discriminator

Beam Intensity (50GeV-15  A) K1.8K1.8BRK1.1/0.8 Max. Mom. [GeV/c] K  Intensity [ppp] 1.8 GeV/c 1.1 GeV/c 0.8 GeV/c 9.6x x x x x x10 6 K/K/ 2.3 (1.8GeV/c)10 (1.1GeV/c)4.3 (1.1GeV/c) Beam Rate [/sec]2.3x x x10 7

High rate への対応 Fine spacing wire chamber – 0.5mm MWPC Semiconductor device –Silicon Strip Detector Fine segment scintillator hodoscope Channel 当たりの計数率を下げる。 Channel 数の増大 低コスト化

0.5mm-Spacing MWPC (1998 東北大） incident angle 10 deg. Efficiency Anode 12  m  1.7mm 0.5mm mm x 50mm ClusterSize =2/CS=1 Ar:iso-C 4 H 10 =7:3 Plateau: kV CS2/CS1: 120% Cathode

0.5mm MWPC – effect of freon - Plateau 特性 Ar:iso-C 4 H 10 =7:3 Cluster Size CBrF 3 1.5% で（安定）動作 Plateau 幅 300V Cluster Size も許容範囲 製造中止 代替 Freon Gas の必要

SSD as focal plane detector at J-Lab E scattered electron spectrometer of (e,e’K + ) experiment 2x10 8 electrons /sec /10 SSDs’ 0.5mm pitch Single-sided 144 strips/board 50mm x 74mm t~300  m binary readout with multi-hit TDC 2x10 -7 /sec/20mm は充分可能 Double-sided structure を２面以上 －＞ Track 再構成可能 Radiation Damage ? bulk conversion p/cm 2

物質量と分解能への影響 [g/cm 2 ] X 0 unit  E [MeV]  0 [mrad] Gas Chamber Ar 30cm Al 0.02mm 5.1 x 10  5.4 x 10  1.05 x 10  2.6 x 10  2.3 x 10  5 x 10  SSDSi 0.5mm x x 10  1.1 x 10  Pla. Scin. Hodoscope 2cm x 10  Eneagy loss stragling ~1/10 of  E Position resolution 0.3mm Pla. Scin. Hodo は 分解能の必要な実験には 向かない。

まとめ 東海に建設中の J-PARC で K ビームを利用したハ イパー核の実験が計画されている。 Phase1 でのビーム強度では、既存の技術で対応 可能。 Phase2 のフル性能では、新たな技術が必要。 – Fine spacing wire chamber (0.5mm MWPC) CBrF3 に代わる Freon Gas, さらなる R&D – Semiconductor Device ( SSD ) 物質量と放射線耐性 回路系の低コスト化が必要