核天體物理組工作匯報革新版

1、Progress of Experimental Nuclear Astrophysics in CIAE,Wei-ping Liuwpliu@iris.ciae.ac.cnChina Institute of Atomic Energy (CIAE)CCAST symposium on physics of isospin and nuclear phase transitionAugust 19-21, Beijing,N

2、uclear Astrophysics,From macro to microNuclear physics in energy production and element synthesisProcess, time scales, environment, isotope abundanceAstrophysical model,Some of the great discovery of astrophysics in 2

3、0th and 21th century,3K microwave background radiation,1965, experimental support for Big-Bang theoryDetection of solar neutrino, 1960, message from solar interiorElement distribution anomaly in metal starDetection of

4、 26Al g-ray, 1980, direct support of explosive nuclear synthesis, development of g-ray astronomyDetection of SN1987A supernova explosion,1987Experimental explanation of solar neutrino missing, 2003,,Exp,The,Nuclear dat

5、a,Astro Obs,,Astro Model,Exp,The,,,,,,,,,The interplay between nuclear physics and astrophysics,,AbundanceEstimation,,Nuclear physics plays role,®RIA white paper 2001,®RIKEN proposal,Important NP data,S-factor

6、, focus on NP, down to astrophysicsReaction rates, direct input to network calculationDirect capture, direct reactionsResonance, level scheme, level width, and partial width,Where is reaction and decay data in network

7、 calculation,Extra low energies,11C(p,?)12N,General idea,Production of RIB ( In-flight method)Measurement of (d,n) or (d,p) angular distribution Fit the distribution by DWBAGet ANC or spec factorUse ANC or spec factor

8、 to deduce (p,g) astrophysical S-factor or (n,g) reaction rate,H. M. Xu, PRL 73(1994)2027,More basics,For peripheral transfer reaction: B(d,n)A,two virtual captures:,B + p ? A n + p ? d,two ANC’s :,and,known va

9、lue,can be obtained from,The Cross Section for E1 capture,,is the kinetic factor,eeff = eN/A for Protons -eZ/A for Neutrons,ANC or spec factor,,BRIF,Tandem: 15 MVCyclotron: 100 MeV p, 200 mA,RIBs expected,B

10、IRFII,,,,,,,,,,,,Inverse kinematics,GIRAFFE,Target,Dipole,Quadrapoles,Reaction,Wien filter,W. Liu, NIMB 204(2003)62,Unstable beams produced,,Secondary beams summary,Now, with velocity filter the new beam and beam purity

11、enhancement:7Be, purity > 99 %17F, 15O, 13N, purity > 90 %10C, new beam, purity > 90 %With the future new beams of 14O and 8B etc by using 3He gas target,15 years of research in CIAE,,,9520002005,,,,,,

12、7Be(d,n)8B, CIAE, PRL96, CPL2000,6He(p,n)6Li, CIAE, PLB2002,11C(d,n)12N, CIAE, NP2003,8Li(d,p)9Li, PRC2005,11C(p,g)12N, TRIUMF,17F(d,n)18Ne, CIAE,,Physics of 7Be,The astrophysical S factor for the 7Be(p,g)8B reaction at

13、solar energies is a crucial nuclear physics input for the “solar neutrino problem”. It was proposed that the S factor can be indirectly determined through the asymptotic normalization constant (ANC) extracted from the p

14、roton pickup reactions of 7Be, with an accuracy comparable to that from direct radiative capture or Coulomb Dissociation reaction.,Results－7Be,W. LiuPRL77(1996)611NPA 616(1997)131c,Physics of 11C,Proton- and a-capture

15、reactions on proton-rich unstable nuclei of A≤13 involved in the hot pp chains are thought to be another alternative way to the 3a process for transforming material from the pp chains to the CNO nuclei in the peculiar as

16、trophysical sites where the temperature and density are high enough so that the capture reaction becomes faster than the competing β decay These linking reactions between the nuclei in the pp chains and the CNO nuclei m

17、ight be of immense importance for the evolution of massive stars with very low metallicities.One of the key reactions in the hot pp chains is the 11C(p,g)12N which is believed to play an important role in the evolution

18、of Pop Ⅲ stars.,From (d,n) to (p,g),Results－11C,W. Liu, NPA728(2003)275,Network calculation,N. Shu, Nucl. Phys. A 758 (2005) 419c,E983@DRAGON,Wei-ping Liu, E983 Proposal,Physics of 8Li,Inhomogeneous model predict that s

19、hort-lived isotopes are created which allow for more reaction pathways to the heavier elementsReactions involving short-lived radioactive nucleus 8Li, 7Be and 8B play key role8Li generating reactions: 7Li(n,g)8Li and 7

20、Li(d,p)8Li，8Li destroying reactions: 8Li(a,n)11B, 8Li(n,g)9Li, 8Li(d,p)9Li, 8Li(d,t)7Li, 8Li(d,n)9Be, etc. 8Li(a,n)11B and 8Li(n,g)9Li are key of them8Li has short half life of 0.83 s, so indirect approach is the onl

21、y way to get (n,g) rates,APJ429(1994)499,Results－8Li,Z. H. Li, W. P. Liu et al., Phys. Rev. C 71, 052801(R) (2005),Some details of calculation 1,In agreement with ANL results, A. H. Wuosmaa et al., PRL94(2005)082502, w

22、hich is 0.90+ - 0.13,Some details of calculation 2,1,Fitted by experimental known 6,7Li and 12C (n,g) reactions,Results for (n,g) rate,Z. H. Li, W. P. Liu et al., PHYSICAL REVIEW C 71, 052801(R) (2005),Application to mi

23、rror system,Angular distribution 8Li(d,p)9Lig.s. @ Ecm = 7.8 MeV ANC of 9Li ?8Li + n is 1.33 +-0.27 fm-1 Charge symmetry, ANC for 9C?8B + p is 1.10 +-0.23 fm-1.S-factor and reaction rate for direct capture in 8B(p,g

24、)9C using the ANC,B. Guo et al., Nucl. Phys., in press,Summary,,,,,,,,Summary of experiments,1.33+-0.27,3970+-950,Summary,GIRAFFE, a tandem based one stage unstable beam facility proved to be effective to produce seconda

25、ry beams suitable for the study of nuclear astrophysics reactions. Angular distribution measurements of transfer reaction in inverse kinematics, together with DWBA/ANC theoretical approach have been used to study the as

26、trophysical reactions indirectly. The astrophysical S-factors and/or reaction rates for 7Be(p,g)8B, 11C(p,g)12N, 8Li(n,g)9Li were deduced by using the measurements of 7Be(d,n)8B ,11C(d,n)12N, and 8Li(d,p)9Li reactions a

27、t the energies of astrophysical interest.,Research Team and support,Bing Guo,Gang Lian,Weiping Liu, wpliu@iris.ciae.ac.cn,Xixiang Bai,Baoxiang Wang,Sheng Zeng,Yun Lu,Zhihong Li,Shengquan Yan,Yongshou ChenNengchuan ShuK