Flow of rp process around 56 Ni

Transcription

1 Flow of rp process around reaction rates for the (p,γ) Cu, Cu(p,γ) 58 Zn, ( (n,p) Co, 64 (n,p) 64 Ga) reactions Naohito Iwasa Department of Physics, Tohoku Univ.

2 Heavier elements than Fe heavier elements than Fe s process r procrss (n,γ) & β - Arnould 003 Arnould, Goriely, Phys.Rep. 384,1 Fig.3 p nuclides (stable) s process r procrss Z p p s s,r process+γ process proton rich region:s p >S n large abundance of 9,94 Mo and 96,98 Ru cannot be explained r r N

3 rp process Schatz et al Proton-rich region (p,γ) & β + (EC) Nova, Xray bursts 0.4GK: A<110 Super Nova 1-3GK: up to 64 waiting points ( ), 64, 68 Se, 7 Kr long life time negative or small Q value for (p,γ) Phys. Rev. Lett. 86 (001) 3471

4 rp process Cu reaction rate : T 1/ = 6 days Q (p,γ) = 0.7MeV As reaction rate 64 : T 1/ = 64 s Q (p,γ) = 0.18MeV Zn 58 Zn 66 Se 65 Se 67 Se Cu Cu 58 Cu 65 As 66 As Co 54 Co 55 Co Co Co 61 Ga 6 Ga 63 Ga 64 Ga : double magic supernova:stop at Zn X ray bursts etc.: up to A=110

5 νp process p + ν n + e e n Ga + p + n Co + p Zn 58 Zn 66 Se 65 Se 67 Se Cu Cu 58 Cu 65 As 66 As Co 54 Co 55 Co Co Co 61 Ga 6 Ga 63 Ga 64 Ga Problem on overabundance of P nuclides may be solved Experimental determination of reaction rates precise predictions of p nuclides Reactions with smaller reaction rates determines reaction rate of the process (p,γ) Cu, ( Cu(p,γ) 58 Zn,) (n,p) Co, 64 (n,p) 64 Ga, 68 Se(n,p), 7 Kr

6 (p,γ) Cu S p =0.695(19),T 1/ =196ms DC component is negligible 1 H( 58, Cu γ): Zhou excited states (1.08, 1.106,.398 MeV) Γ γ are not determined. H(,p) : Rehm Zhou et al.,phys. Rev. C53, 98 Fig.

7 (p,γ) Cu S p =0.695(19),T 1/ =196ms DC component is negligible 1 H( 58, Cu γ): Zhou excited states (1.08, 1.106,.398 MeV) Γ γ are not determined. H(,p) : Rehm C S of same C S was used for Cu assuming the charge symmetry. C S(5/ - )= 0.91 C S(1/ - )= 0.90 Rhem et al.,phys.rev.lett. 80,676 Fig.1 Rhem et al.,phys.rev.lett. 80,676 Fig. Rhem et al.,phys.rev.lett. 80,676 Fig

8 (p,γ) Cu S p =0.695(19),T 1/ =196ms DC component is negligible 1 H( 58, Cu γ): Zhou excited states (1.08, 1.106,.398 MeV) Γ γ are not determined. H(,p) : Rehm C S of same C S was used for Cu assuming the charge symmetry. More reliable determination is necessary Rhem et al.,phys.rev.lett. 80,676 Fig.4 Rhem et al.,phys.rev.lett. 80,676 Table 1

9 Cu(p,γ) 58 Zn No experimental data Forstner, Phys. Rev. C64, , 001 Experimental determination of E x, Γ p and Γ γ is necessary. + >1GK 0 + not AP GK 1 + not AP p + <0.4GK Sp=.8(5) 4 + not AP 3/ - 196ms Cu 58 Zn ms Forstner, Phys. Rev. C64, Table 5 Forstner, Phys. Rev. C64, Fig. 3

10 Coulomb dissociation method The Coulomb dissociation method is powerful tool to deduce radiative capture cross sections relevant to nuclear astrophysics. RIB + Pb γ Doppler corrected γ energy RI beam A Excitation virtual photon Pb breakup B protons, neutrons, charged particles invariant mass energy of excited states A+Pb B+p+Pb Virtual photon theory dσ de CD B+p(n) A = σ πλ πλ (p, γ ) n πλ (I p + 1)(I (I B Be + 1) + 1) μc E ( E + Q) 3 A+γ B+p Detailed valance B+p A+γ

11 Coulomb dissociation studies on (p,γ) reactions Γ p >> Γ γ σ v = Γ p 3 π μkt Γ γ h ΓpΓ ω Γ γ E exp R kt Γ p << Γγ σv 3 π μkt h ω Γ γ exp E R kt 3 π E x (inv. Mass & E γ ) σ v μkt reaction rate Energy (E γ ) h ω Γ p exp E R kt E x (inv. mass) Γ γ reaction rate reaction rate difficult? CB cross section is too small. Alternative method?

12 Experimental setup in RIBF We are planning to perform measurements of reactions in the rp and r processes in RIBF. rp process (γ,p) proton DC+ plastic DC+ IC+plastic, Cu BigRIPS Cu, 58 Zn γ-detectors γ 6xSSD SAMURAI B+p(n) A

13 Cu(p,γ) 58 Zn >1GK not AP GK 1 + not AP p + <0.4GK Sp=.8(5) 4 + not AP 3/ - Cu + Γ p Γ p Γ p >> Γ γ /10 Γ γ << Γ γ Excitation energy, reaction rate Excitation energy, reaction rate branching ratio Excitation energy 196ms 58 Zn ms The reaction rate will be determined from an experiment of the Coulomb dissociation of 58 Zn. Forstner, Phys. Rev. C64, Fig. 3

14 (p,γ) Cu Rehm et al., Phys. Rev. Lett. 80, 676, 1998 Rhem et al.,phys.rev.lett. 80,676 Table 1 g.s. 3/ and MeV states Γ p <<Γ γ : CD Γ p <<.398 MeV states: M1/E mixture CD angular distribution M1/E ratio? branching ratio.50 MeV states: E CD Γ γ Rhem et al.,phys.rev.lett. 80,676 Fig.4 Reaction rate for T>1.GK can be determined. For T<1.1GK,?

15 To determine Γ p from experiments Γ p <<1 ev: Transfer reaction Γ p = C SΓ SP p S: determined from experiments stripping reaction (d,n) in reverse kinematics energy and scattering angle of neutron should be measured, precisely to select ex. states. thermal neutron? scattering? efficiency? Rehm et al. +d Cu+n +p +d Cu+n+γ at ~50AMeV Rehm +d *+p 8AMeV σ tot ~0mb Cu+n+γ at 40AMeV assuming 1mb? 5mm Liq. (Sol.) D target (energy deposit: 17AMeV) beam 100 cps, gamma eff.~0% Cu eff.~80% 35 counts/day? Separation of the 1.08 and MeV state? feeding from higher excited states?

16 ( 3 He,d) reaction in reverse kinematics ( 3 He,d) reaction Iliadis and Wiescher, PRC69, (004) dσ = N dω J f dσ C S J + 1 j + 1 dω i DWBA N = 4.4 for ( 3 He,d) by P.D. Kunz 3 He(,d Cu) (p,γ) Cu 108, 1106 kev states Γ p <<Γ γ C S~0.9 estimated by Rehm σ DWBA A MeV Hale et al. PRC70, 04580(004) 3 Na( 3 He,d) 4 Mg (p,γ), (p,α) Reverse kinematics & RI?

17 A example of experimental setup MCP 0.5μm Silicon PSD 4 ( , pitch 5) d 3 He gas SSD 10μm SSD reaction: ( 3 He,p), ( 3 He,d), ( 3 He,p) Back scattering ( 3 He,d), ( 3 He,p), Cu 6AMeV Beam? 10 4 cps 5mm t3 He gas 1mb Efficiency 50% Ed ΔE-E Ed 0 10 ( 3 He,d) Cu ( 3 He,p) g.s E in =5 AMeV 1.08 ~5 event/day Higher energy? θ θ lab CM

18 To determine the (n,p) cross section (n,p), 64 (n,p), 68 Se(n,p), 7 Kr(n,p) reactions are of crucial importance to determine reaction rate of the νp process Q=-0.0MeV Q=-0.71(10)MeV 70 Q=0.70MeV Q=0.18MeV Kr t 1/ =36s 7 Kr t 1/ =17.s t 1/ =6days t 1/ =64s Cu 65 As 70 Br 7 Br Se 69 Se 7 Kr 73 Kr S. Ota Co 64 Ga 68 As Determination with the direct method is impossible because both, 64 and neutron are not stable (radioactive). Beta decay: σ (n,p) (0) B(GT), B(F) Alternative method is desired to determine the (n,p) cross section. To study B(GT), (d,p) reactions in reversed kinematics. 7 Br

19 (d,p) reaction in reverse kinematics n p Co Co H He E He [MeV] He+ Co+ He E( )=10AMeV Ex:0,1,,5,10 MeV E He [MeV] E( )=50AMeV θ He θ He

20 A example of experimental setup PPAC Silicon PSD+CsI(Tl) p PA / SHARAQ p, Se, 7 Kr Co, 64 Ga 68 As, 7 Br collaboration with S. Ota s group detectors for proton will be discussed Se 7 Kr Problem: charge states of Co, Ga, As, Br E He [MeV] He+ Co+ He E( )=10AMeV Ex:0,1,,5,10 MeV σ(0) θ He

21 まとめ (p,γ) Cu Cu(p,γ) 58 Zn 反応率の実験的導出クーロン励起 ( 分解 ) 反応 : 強力な道具 (Γ p >>Γ γ, Γ p ~Γ γ :SN) reaction rate, branching ratio Γ p <<Γ γ (nova): 逆運動学の ( 3 He,d) 反応 6AMeV,10 4 cps 以上の ビーム 実験可能 (n,p) Co, 64 (n,p) 64 Ga, 68 Se(n,p) 68 As 逆運動学の (d, He)? (t, 3 He)? charge state 問題 Heが標的中に停止 薄い標的 (t, 3 He): 放射性同位体標的 (t,pd)(t,np) と分離可能か?