SAMURAI (Superconducting Analyzer for MUlti-particles with RAdio-Isotope beams) 超伝導スペクトロメータ 　大ギャップ  複数粒子同時計測 多様な用途 Coulomb Breakup ( ,n) ( ,p) Nuclear Astrophysics (p,2p) missing mass pol-d induced reaction　for 3NF Nuclear matter ….. 超伝導双極電磁石 7Tm bending power Large gap 80cm Weight ～600 ton RI ビーム （from BigRIPS ） ポール（直径2m.) コイル 2011年夏　 稼働開始に向けて Project Manager ・ 契約関連業務 39契約の統括、物品管理 ・ 共同研究の旗振り 東北大、東工大、京大… 標的 n 中性子 陽子 重イオン

RIBF030 “In-beam gamma spectroscopy of the doubly magic nucleus 78Ni and its vicinity” approved for 10 days In collaboration with gamma group … waiting for high enough uranium beam intensity Coulomb breakup for nuclear astrophysics Coulomb breakup (g,p) – inverse of resonant capture (p,g) 23Al Coulomb breakup paper – to be finalized In charge of proton detector in SAMURAI collaboration silicon strip detector with 5000 dynamic range – Togano for details ANC measurement with breakup reaction in collaboration with Texas A&M RIBF13 “Breakup of loosely bound nuclei at intermediate energies for nuclear astrophysics” approved for 3 days DOE proposal “Breakup of loosely bound nuclei at intermediate energies for nuclear astrophysics and the development of a position sensitive microstrip detector system and its radout electronics using ASICs technologies” notified to be approved

重イオン – 陽子 breakup 測定による 天体核反応の研究 理化学研究所 仁科加速器研究センター 米田健一郎 ２００９年３月２７日 日本物理学会 第６４回年次大会 シンポジウム「SAMURAI スペクトロメータで拓く核物理」

Outline Introduction RIBF BigRIPS と SAMURAI スペクトロメータ Nucleosynthesis と 不安定核の (p,g) 反応 RIPS での Coulomb breakup 測定 RIBF BigRIPS と SAMURAI スペクトロメータ さらに重い不安定核領域へ 想定している実験セットアップ Breakup 反応によるANC測定の試み まとめ

陽子過剰側での元素合成過程：rp-process Nova, g-ray burst などの 　　　　　　　　　高温高圧環境下 爆発的水素燃焼 陽子捕獲反応 b 崩壊 が連鎖的に起こり重い元素を合成 理解することは重要 元素の天然存在比（特にp-nuclei） cosmic g-rays from 　　　ongoing nucleosynthesis Energy production in stars ….. 不安定核の陽子捕獲断面積が必要 { Ne nova M.Wiescher et.al. Phil. Trans. R. Soc. Lond. (1998)

ネットワーク計算には多数の不安定核の反応レートが必要 短寿命核　– 実験研究が困難であった 核理論ベースの計算　 常に正しいわけではない 　c.f. 不安定核での殻構造の変化、変形領域の発現  実験情報に基づくことが望ましい 最近の重イオン加速器、 　　　　　　　　　不安定核施設の発達 　　 短寿命核の反応研究の絶好機 これまで我々のグループでは 　間接測定による研究 　14N(p,g)15O 22Mg(p,g)23Al 26Si(p,g)27P 30S(p,g)31Cl ….. Thielemann et al., Prog. Part. Nucl. Phys. 46 (2001) 5.

クーロン分解反応 -- (p,g) 反応の逆過程 -- γ Cross section far larger 22Mg 23Al* p Incident beam 22Mg + p 23Al High-Z target (Pb) 22Mg(p,g)23Al 23Al(g,p)22Mg 26Si(p,g)27P 27P(g,p)26Si s ~ 60nb s ~ 4mb Inverse reaction Cross section far larger Detailed valance + virtual photons

共鳴捕獲反応 -- Gg の重要性 -- ~ Gg Gg を決定することが重要 クーロン分解反応で測定する断面積  B(E2)  Gg 共鳴捕獲強度 wg GgGp 2j+1 Gp wg = Gg (2j1+1)(2j2+1) Gg+Gp 22Mg + p ~ Gg when Gg << Gp 23Al Gg を決定することが重要 クーロン分解反応で測定する断面積  B(E2)  Gg

Experimental Setup -- RIPS -- “Old” part of RIKEN Accelerator facility Primary beam Energy on target Rate Purity 23Al 28Si 135 AMeV 50 AMeV 7x103 ~7% 27P 36Ar 115 AMeV 57 AMeV 2.8x103 ~1% 9

Experimental setup - Detectors for Heavy Ion and proton - 22Mg Energy Angle Heavy Ion Proton of 不変質量を導出, 相対エネルギースペクトル

相対エネルギースペクトル - 23Al  22Mg + p - 1st excited state (objective state) Higher excited state continuum component: E1 , constant astrophysical S -factor Counts /150keV 1000 2000 3000 4000 Relative energy [keV] ・ energy resolution 170 keV (Erel = 400 keV) ・ identify reaction through the first excited state clearly.

Cross sections - 23Al  22Mg + p - Coulomb + Nuclear l = 2 23Al 22Mg P 23Al * l = 1 “βC” = “βN” Small “Nuclear” component : 8 % l = 2 distorted-wave calculation optical potential : 17O+208Pb (84AMeV) collective (vibrational) model Coulomb ONLY Coulomb + Nuclear Coulomb and nuclear response is considered as same deformation parameter. Nuclear ONLY = (9.1 ±2.0) × 10-7 eV Compatible with the predicted value by J.A. Caggiano et.al. Phys. Rev. C 64 (2001) 025802. 5.49×10-7 eV

Competition with b decay Nucleosynthesis in explosive hydrogen burning (Novae, X-ray bursts) 0.1 0.2 0.5 1.0 2.0 T [GK] 106 104 102 100 ρ [g/cm3] Which? Nova Model M1 : J.Jose et al Astrophys. J. 520 347 (1999) M2 : C. Iliadis et.al. Astrophys. J. Supp. 142 105 (2002) Cosmic γ-emitter Ne nova M.Wiescher et.al. Phil. Trans. R. Soc. Lond. (1998) βdecay is favored

さらに重い領域へ Requirements 重い領域へ展開したい ・ 重い不安定核の生成 ・ 実験の分解能の向上 　　rp-process の waiting point となりうる所での反応レート 　　p-nuclei の起源、天然存在比の理解 Requirements ・ 重い不安定核の生成 RIPS　 RIBF + BigRIPS ・ 実験の分解能の向上 Silicon Telescope SAMURAI spectrometer resolution ~ 1/700 up to 100Sn Thielemann et al., Prog. Part. Nucl. Phys. 46 (2001) 5.

Production rates (fragmentation) SRC → BigRIPS Maximum All beams: E= 350AMeV, I=1pμA 136Xe 48Ca 86Kr 56Ni 64Ge 100Sn AVF + RRC

PI, momentum of Heavy ion low resolution mode high resolution mode PI, momentum of Heavy ion PI, momentum of proton(s) Strip Silicon Detectors emission angles of products Strip Silicon Detectors Simultaneous detection of HI and p (sometimes 2p) Small multiple scattering effect Position measurement for relative angle

Silicon Strip detectors for proton breakup at SAMURAI HEAVY ION A/Z ～ 2 Developments Required Broad Dynamic Range Both proton & HI (Z<50) hit the detector Low-noize (non-linear?) Preamplifier Low-noize circuit board & wire bonding Capability of high density signal processing signals of about 2500 ch in total Modify integrated ASD circuit HINP16C in collaboration with Texas A&M and Washington Univ. in St. Louis HINP16C – 16ch processing in 1 chip two output for energy and timing PROTON Silicon Strip (x, y, (diag)) x2 HPK “GLAST” silicon 87mm x 87mm, 228 mm strip RI Beam e.g. 64Ge T. Ohsugi et al., NIM A541 (2005) 29

Breakup反応によるANC測定 (in collaboration with Texas A&M) ANC in peripheral reactions: radiative proton capture, breakup and transfer breakup happens here (p,g) happens here Shape in asymptotic region given by Whittaker fct. Only normalization (ANC) unknown and needed!

Breakup reactions for nuclear astrophysics Momentum distributions → nlj Cross section → ANC (only!!!) Gamma rays → config mixing Need: Vp-target & Vcore-target and reaction mechanism model 　 stheory for a certain amplitude sexp/stheory  ANC

Summary Study of nucleosynthesis Important to understand our nature Processes involve RI reactions difficult to measure reaction rates RIBF – providing big opportunities for study of RI reactions relevant to nuclear astrophysics SAMURAI spectrometer Proton breakup reactions reachable up to 100Sn Silicon strip detector – readout to be developed Breakup reaction for ANC to be performed

Collaborators T. Motobayashi, M. Kurokawa, Y. Togano, H. Murakami – RIKEN Nishina Center N. Iwasa – Tohoku University We welcome your participation

Location of the reactions (p,γ) reaction sd-shell region Far from the stability p-shell region

Comparison with direct capture NA<sv>(cm3mole-1s-1)) 10-1 22Mg + p 23Al Which is dominant ? 10-10 Resonant capture Direct capture 10-19 0.1 1 T(GK) Resonant capture does not change the reaction rate significantly

Improvement in near future Increase of Radioactive Beam Intensities RARF RIPS  RIBF BigRIPS Improvement of the detector system Heavy Ion detector system Silicon telescope  SAMURAI Spectrometer Resolution 1/700 – up to A ~ 100

Improvement in near future Increase of Radioactive Beam Intensities RARF RIPS  RIBF BigRIPS Improvement of the detector system Heavy Ion detector system Silicon telescope  SAMURAI Spectrometer Resolution 1/700 – up to A ~ 100

SAMURAI (Superconducting Analyzer for MUlti-particles with Radio-Isotope beams) Superconducting magnet 7Tm bending power Large gap 80cm Weight ～600 ton RI beam （from BigRIPS ） Superconducting spectrometer for multi-particle detection Versatile usages Coulomb Breakup ( ,n) ( ,p) Nuclear Astrophysics (p,2p) missing mass pol-d induced reaction for 3NF study Nuclear matter ….. pole（2m dia.) coil target n Neutron Proton Heavy Ion

Silicon Strip detectors for proton breakup at SAMURAI HEAVY ION A/Z ～ 2 HPK “GLAST” silicon 87mm x 87mm, 410 mm thick 228 mm strip (384 strips / detector) PROTON Silicon Strip (x, y, (diag)) x2 RI Beam e.g. 64Ge T. Ohsugi et al., NIM A541 (2005) 29

Special Requirements for the readout circuits Broad Dynamic Range Both proton & HI (Z<50) hit the detector Low-noise (non-linear?) Preamplifier Low-noise circuit board & wire bonding Capability of high density signal processing signals of about 2500 channels in total integrated ASD circuit HINP16C in collaboration with Texas A&M and Washington Univ. in St. Louis by using US DOE Proposal

Breakup反応によるANC測定 (in collaboration with Texas A&M) Breakup 反応 X  Y + p ; A  B + n

Breakup reactions for nuclear astrophysics Peripheral Momentum distributions → nlj Cross section → ANC (only!!!) Gamma rays → config mixing Need: Vp-target & Vcore-target and reaction mechanism model