(g, n) (g, p) experiment at SAMURAI RIKEN Nishina Center Ken-ichiro YONEDA 22 Dec, 2009 Detector Workshop for RIBF experiments

SAMURAI (Superconducting Analyser for MUlti-particles with Radio-Isotope beams) Spectroscopy of Unbound States e.g. (g,n) (p,2p) Missing Mass Nucl. Astrophys. (p,g) Deuteron expts for 3NF Nucl. Matter Bending Magnet Superconducting Large B・L (7Tm) Large pole gap (80cm) Weight ~ 600 ton Neutron Tokyo Tech. Group (Prof. Nakamura) in charge d setup TPC Heavy Ion (not shown in picture) Proton (not shown in picture)

Invariant Mass Method 12Be 14Be 14Be* n n 12C target 2+ Erel Ex 12Be+n+n S2n=1.26(13)MeV 0+ Scattering angle q T.Sugimoto et al.PLB654,160(2007). 3

Coulomb Breakup Inelastic Scattering 19C+p→18C+n+X 17C+p→17C+n+X 11Li+Pb→9Li+n+n+X T.Nakamura et al., PRL 96, 252502 (2006) Y.Satou,TN et al., PLB 660, 320 (2008).

Physics of Neutron-rich Nuclei via Invariant Mass Method (@SAMURAI/NEBULA) Structures and reactions of r-process nuclei Giant and Pigmy resonances of Neutron-skin nuclei Neutron Star/Nuclear Matter 82 r-process 126 50 82 28 20 50 Drip-Line Physics Giant Halos? 2n, 4n-correlation? New Cluster/Molecular States? States beyond drip-lines? (4n,28O, and more) 8 28 20 2 8 2

NEBULA Typical Setup Detectors: To be installed in the vertical direction To cover more acceptance in the horizontal direction 1.8m (12cm thick x 2 layers) X 4 Walls 3.6m

NEBULA Modules Neutron Detector Module Veto Detector Module 32cm 12cm Plastic Scintillator (BC408) 12cm(H)x180cm(H)x12cm(D) Coupled to 2 PMT’s (HAMAMATSU R7724ASSY) Veto Detector Module Plastic Scintillator (BC408) 32cm(H) x 190cm(H) x 1cm(D) Coupled to 2 PMT’s (HAMAMATSU R7724ASSY) 180cm 190cm VETO Module Neutron Module

Typical Setups of NEBULA 1n + core fragment 1-stack configuration 4n + core fragment 4-stack configuration 3.6m ~1m gap 10 m @250MeV/u

Acceptance 2n acceptance 1n acceptance Acceptance is dictated by neutron Basic setup Horizontal -10deg~+10deg, Vertiacl -5deg~+5deg 1n acceptance 1n acceptance 2n acceptance Smooth dependence and sufficient acceptance up to Erel=10MeV(40%) 2n acceptance has nearly identical E-dependence to that of 1n acceptance

Intrinsic efficiency for neutron Estimation of Resolution 96cm 48cm 12cmx12cm dimension is o.k. In terms of the energy resolution Thickness: 96cm  ~66% (Thickness of 2m does not enhance the efficiency very much) Current (Half is funded)~40%

Current Status and Schedule Half the neutron detector modules(120) +Full Veto Modules (48) are funded 1n efficiency~40%, 2n efficiency ~10% (170 M JPY ~1.6M USD, 1MJPY/1module) For the funded part, Plastic Scintillators+PMT’s are available by the end of March 2010 (Modules for 1Layer already installed) Electronics modules are available by the middle of 2011

Reaction Study for Nuclear Astrophysics Very hot dense enviroment particle capture b decay occurs sequentially Important to understand Natural abundance Ongoing nucleosynthesis from cosmic g-rays Energy production in stars ….. { Ne nova M.Wiescher et.al. Phil. Trans. R. Soc. Lond. (1998)

Nuclear Astrophysics Studies with Radioactive Isotope Radioactive Isotopes are included Short-life nuclei – hard to study Structure theories are used – not always valid change of shell structure, shape,…  Experimental information is desired Recent development of RI beams In-flight fragmentation (fission)  providing great opportunities to study short-life RI reactions

Coulomb Breakup Reaction -- Inverse of (p,g) reaction -- 22Mg 23Al* 23Al γ 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

Experimental setup - Detectors for Heavy Ion and proton - 22Mg Energy Angle Heavy Ion Proton of Invariant mass, Relative energy spectrum

Relative Energy Spectrum - 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 = (7.0 ±1.3) × 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.

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  NEXT Talk by Kurokawa san for more technical details T. Ohsugi et al., NIM A541 (2005) 29

Summary (gamma, n) experiment (gamma, p) experiment Invariant mass spectroscopy of neutron-rich isotopes NEBULA detector 40% efficiency (Full volume), 100% coverage up to Erel ~ 3MeV Half volume ready in March 2010 (gamma, p) experiment Mainly for nuclear astrophysics interests Silicon strip detector Readout requires 1:5000 dynamic range 2500 ch high dense signal prosessing  NEXT Kurokawa san’s talk