Experimental Study of Stellar Reactions at CNS Shigeru KUBONO ( 久保野茂 ) Center for Nuclear Study (CNS) University of Tokyo 1. Nucleosynthesis under Explosive Conditions + CNS-RIKEN AVF-Upgrade Project 2. Direct Study of the Stellar Reactions 3. High Resolution Spectroscopy for Proton Resonances 4. Scope
Nucleosynthesis Scenarios pp-chain H-burning @small M Proton Number @Novae, X-burst H-burning Hot pp-chain αpprocess rpprocess CNO Cycle H-Burning @large M @Giants s-process Explosive Phenomena α- process Neutron Number 90 Th, 92 U r-process n-reactions @SN, Unstable Nuclei @low energies
Low Energy RI Beam Production
How to Produce RI Beams? Low Energy High Energy ISOL LLN none -based TRIUMF Method ORNL TRIAC, Not much developed! In-flight Notre Dame GSI, MSU Method ANL RIKEN, Beijing Lanzhou, CRIB/CNS GANIL
RI Beams by In-Flight Method RIB intensities reaction type 10 4 pps Resonant scattering w/thick target method eg. 22 Mg+p 10 6 pps Rearrangement reactions eg. (α,p), (α,n), (d,p),... 10 8 pps (p,γ), (α,γ),... Total system development; 1. Ion source 2. Accelerator 3. Beam transport 3. Production target 5. Separator
CNS Facilities at RIKEN (Under CNS-RIKEN joint venture) RIBF PA Another Facility in RIKEN AVF-BT Campus CRIB Ge Parallel processor system (Theory/Otsuka) CNS-BT AVF /HyperECR CSM AVF Upgrade Project
F1: Momentum Dispersive Focal Plane -MomentumSlit - Degrader (thin foil) Degrader Low-Energy in-flight RI Beam F1 RIB ~ 10 3-6 pps at F3 ΔE/E ~ 0.5 1 % Purity ~ 90-100 % Q RI Beam 0 5 m Separator CRIB F0 Production target F0: Production Target Gas target with window foils Primary Beam (Low-Energy HI) F2 From RIKEN AVF Cyclotron F2:Achromatic Focal Plane Experimental setup Q Q Q Q B E Wien Filter System (under construction) Wien Filter F3 F3 From AVF
Beam Size of 14 O at F3 Wien Filter -> 100 % 14 O of > 10 6 aps Y (mm) ~ 7 x 6 mm 2 Without a degrader Small spot size Higher order correction X (mm) Smaller RI beam spot size!
7 Be Beam Production at CRIB 4-MeV 7 Be beam of 6x10 6 aps available! (w/ 0.5 pμa) More beam available! ( > 50 pμa) (Limited by the production target) 7 Be(p,γ) 8 B Reaction: ; Solar model, first generation stars
RIB Intensity to Be Reached at CRIB Production target Liq. N 2 cooling target Primary beam intensity SuperC. ECR/Tsukuba U. Upgrade the cyclotron Central region/ Dubna Z 10 8 pps direct measurement of (p,γ) reactions 2 10 8 available 10 7 10 6 N 105
Direct Study of the Stellar Reactions
Nuclear Reactions in the Sun - pp-chain High energy neutrino 8 B 8 Be+e + +ν Proton numbers Neutron numbers
8B Structure? Nuclear structure of 8B Solar Model First generation stars Supernovae
Elastic Resonant Scattering of p + A(RIB) (Thick target method) Y( E) = I( E) σ( E E+ Δ E/ 2 i E ΔE/ 2 ε( Ei ) ) de i I(E) : Number of beam particles ε(e) : Stopping cross sections
Q F0: Production Target Gas target with window foils Primary Beam (Low-Energy HI) 7 Be+p: Setup il) From RIKEN AVF Cyclotron F2:Achromatic Focal Plane Experimental setup 7 Li from AVF cyclotron Q Q Q Q B E F3 RI Beam Wien Filter System (under construction) Primary beam: 7 Li 3+, 61.9 MeV (8.76 MeV/u), ~100 pna. Production target: Hydrogen gas (0.67 mg/cm 2 ), 7 Li(p, n) 7 Be. Secondary beam: 7 Be 4+, 53.8 MeV (@ secondary target), 5 x 10 5 pps, 100% pure.
Direct Measurement of the αp-process Reaction
High T rp-process (e.g. X-ray burst, SN) 14 O(α,p) 17 F
14 O(α,p) Stellar Reaction Both 6.15 and 6.29 important Transition to 17 F*(0.495) important Branching ~ 1/2
Astrophysical Reaction Rate 14 O+α 18 Ne * (7.05,(4+)) 17 F * +p 6.15 +6.29 New transitions enhance the reaction rate through the 7.05- MeV level This implies the temperature at cross point of 6.15- and 7.05-MeV curves reduced. B. Harss et al., PRC65 p035803 (2002)
Proton Resonance Search for rp-process Nuclei
Early Stage of rp-process Breakout process from NeNa Cycle Production of 22 Na Studied recently.
Spectrum of 22 Mg+p Scattering C ounts / 35 k ev b in 100 80 60 40 20 o @ θlab 0 Ex: 3.13 3.29 (inelastic) E (MeV) cm (elastic) 3.00 (inelastic) 3.98 0.5 1.0 1.5 2.0 2.5 3.0 22 Mg(2 + 1 ) + p 23 16 0 Expt. Calc. (inelastic) Calc. (elastic) E= x 3.13,3.29,3.00,3.98 2.0 2.5 3.0 3.5 E (MeV) cm
23 Al Level Scheme in 23 Al Present; 22 Mg+p + (7/2 ) + + (7/2,5/2 ) + + (7/2,5/2 ) (3/2 + ) Present 22 Mg+p 3.95(30) 3.26(30) 3.14(30) Shell-model + 7/2 3 3/2-1 5/2+ 3 3/2+ 3 7/2+ 2 1/2+ 2 3/2+ 2-1/2 1 + 9/2 1 + 5/2 2 + + 4.394 4.178 3.826 3.778 3.605 3.494 3.237 2.828 2.516 2.183 1.767 1.759 24 7 8 Mg( Li, He) 3.699(24) 3.204(21) 2.575(34) 1.773(35) 23 Al( γ, p) 2.0 1.37; 2 + + 1/2 1 0.991 0.12; 0 + 22 Mg+p 0 + 5/2 1 0 0.550(20) (1/2 + ) 0 (5/2 + ) 0 0.5 23 Al
Comparisons E x J π expt J π calc l Γ p,(p ) exp Γ p,(p ) cal 0.55 (1/2 + ) 1/2 1 + 0 0.074 1.77 (3/2 + ) 3/2 1 + 2 1.0 Good tool to study weak-coupled 32(5), 17(3) structure! 3.00 (3/2 +, 5/2 + ) 3/2 2 + 2 3.14* (7/2 +, 5/2 + ) 7/2 2 + 2 30(20) 6 3.26* (7/2 +, 5/2 + ) 5/2 3 + 0 30(20) 10 3.95* (7/2 + ) 7/2 3 + 2 30(20) 18 * Their widths are for the decay branches to the 1 st ex. state in 22 Mg. (Ex. energy in MeV and width in kev) 44
High-Resolution Spectrograph PA and the Activities
High-resolution magnetic spectrograph PA beams A target Focal Plane Det. (X1, X2, Y1,Y2 ΔE, E, TOF)
RILAC RIKEN Ring Cyclotron Beam Line for PA 120 MeV α Slit For high resolution mode. E2 PA
Elastic scattering at 10 degrees Target : Mylar (t~1.5um) Beam : 4 He 2+ (K.E.~120MeV) E Lab (α) = 120 MeV 12 C (g.s.) 16 O (g.s.) PA angle : 10 degrees PA slit : 0.1 msr Counts 12 C (1 st ) FWHM~ 40 kev Beam transportation : dispersion mode Beam slit width ~ 0.3 mm Relative momentum (ch)
(1.8-MeV γ by COMPTEL) New Astronomy by satellites and high resolution telescopes (like by SUBARU) =Observation of Isotopes (not elements) Mapping of 26 Al Gamma Rays Our Galaxy 25 Al(p,γ) 26 Si(3 +?) T 1/2 =0.74 My Galactic plane
Scope
RIBF Project at RIKEN CRIB 2 Linac 3 Ring Cyclotron 1 Ion Source Present facility 0 50 m 4 frc Highest-energy cyclotron Highest intensity RI beam factory r-process rp-process p-process 5... IRC CNS-SHARAQ Under construction (2006 first beam!) 6 SuperCond.RC (8000 tons)
Available RI Beams at RIBF RI Beam Intensity at the RI Beams Factory 100 Primary beam of 1 pµa is assumed. Calculated by Intensity II By Nakamura 82 Proton numbers Z 50 St able Unst able limit of Tachibana 50 126 Production rate ~ 10-5 /s 8 8 20 28 20 28 82 50 50 N Neutron numbers 0 10 0.0 10.0 10 10 No. of particles per second 100 Nuclear Chart 1993 by Chiharu Tanihata (from Tanihata)
Subjects Understanding of the r-process: - Evolution of the Early Universe Cosmo-chronology, Mechanism of Supernovae Pathway Second, third peaks Details around the waiting points The time dependence - Mass (separation energy), Magicity, Half-life, resonances, fission process,..
Low-Energy RIB intensity to be reached at CRIB 10 8 pps direct measurement of (p,γ) reactions Beam size < 5 x 5 mm 2 Z Another Intensive facility at RIKEN N available 2 10 8 10 7 10 6 105
Major part of AVF operation will be available for CRIB (& PA) now on CNS-PAC ; early December, every year Catania, Hanoi, McMaster, Kyushu, RIKEN, Korea, Canberra,... 46 days ; 2006 Maybe more time in near future. on Nuclear Astrophysics, Nuclear Physics Material Science,... http://www.cns.s.u-tokyo.ac.jp/crib/crib-intro.html (or mail to KUBONO@cns.s.u-tokyo.ac.jp)
Summary 1. Small machine facility can produce low-energy RIB of 10 8 pps. 2. Direct approach with low-energy RIB for - primordial NS, rp-process, hot pp-chain, early stage of SN, r-process will be possible in near future. 3. The r-process nuclei with very short-half-lives can be investigated with SHARAQ at RIBF.