Experimental studies using radioactive beams at European large-scale facilities

Transcription

1 Experimental studies using radioactive beams at European large-scale facilities Klaus Sümmerer, GSI Darmstadt (Germany) European large-scale facilities: 1. CERN Isolde and n_tof CH ISOL+postacc., sec.neutrons 2. CRC/UCL Louvain-la-Neuve B ISOL+postacc. 3. GANIL Caen F fast sec. beams, ISOL+postacc. 4. GSI Darmstadt D fast sec. beams 5. JYFL Jyväskylä FIN IGISOL 6. KVI Groningen NL fast stable beams 7. LNL Legnaro I stable beams

2 Astrophysical activities at European large-scale facilities General remarks: there is no clear distinction between nuclear-structure research and nuclear-astrophysics studies; many activities at LSF to measure masses, half-lives, level schemes, spin assignments etc. with relevance for astrophysics not presented in this overview; overview is given by a non-specialist comments and clarifications welcome! Presentation of each facility: overview over the facility, beams, equipment; summary of astro-related activities; presentation of selected example(s); future plans to be discussed in the round-table discussion.

3 1. CERN-ISOLDE implantation and decay no astro activities so far with postaccelerated REX-ISOLDE beams

4 Astrophysical activities at CERN: ISOLDE 1. Decay spectroscopy of mass-separated nuclei to study level schemes e.g.: 12 Be β - 12 B β - 12 C* ααα relevant for triple-α process 2. Decay spectroscopy (β-, γ-, βn-decay) of mass-separated p- and n-rich nuclei to obtain Q β -values, half-lives, P n values, and level schemes e.g. properties of 130 Cd, 129 Ag waiting points relevant for rp- and r-process path, isotopic anomalies 3. ISOLTRAP mass measurements of mass-separated nuclei relevant for r- and rp-process path

5 12 C from the β-decays of 12 N and 12 B ISOLDE (15.3) (2 + ) (11.5) (2 + ) 0, JYFL fynbo@phys.au.dk 0 0 +

6 Combined fit of 12 B and 12 N 1. Select 8 Be 0 + channel 2. Divide by different detection efficiency 3. Divide by different β-phase space 4. Normalize fynbo@phys.au.dk

7 Implications for the triple-α rate interference of 0 MeV with Hoyle res. NACRE no 2 + res. at 9.1 MeV fynbo@phys.au.dk C. Diget

8 The n_tof facility at CERN proton beam momentum intensity (dedicated mode) repetition frequency pulse width n/p 300 lead target dimensions cooling & moderation material moderator thickness in the exit face neutron beam dimension in EAR-1 (capture mode) 20 GeV/c 7 x protons/pulse 1 pulse/2.4s 6 ns (rms) 80x80x60 cm 3 H 2 O 5 cm 2 cm (FWHM) alberto.mengoni@cern.ch

9 n_tof beam Neutron intensity

10 Priority (n,γ) measurements Target Motivations & Notes 24,25,26 Mg Isotopic abundance ratios in stellar grains. Importance of 22 Ne(α,n) 25 Mg for the s-process neutron balance. Light nuclei, small cross sections. 90,91,92,93,94,96 Zr s-process branching at A=95 & observed abundance patterns in stellar grains. Sensitivity to neutron flux during the s-process. 93 Zr(τ 1/2 = 1.5 Myr) to be measured in La Bottleneck in the s-process flow. N=82 neutron shell closure. 151 Sm s-process branching at A Sm is radioactive (τ 1/2 = 93 yr). 186,187,188 Os Nuclear cosmochronology (Re/Os clock). 204,206,207,208 Pb, 209 Bi s-process branching at A 185. Termination of the s-process. Small σ γ /σ el. alberto.mengoni@cern.ch

11 The s-process s path at 151 Sm Gd Eu 152 Gd 153 Gd 154 Gd 155 Gd 156 Gd 157 Gd 151 Eu 152 Eu 153 Eu 154 Eu 155 Eu 156 Eu 151 Sm is radioactive with a half-life of 93 years The β-decay rate of 151 Sm depends on T Sm 150 Sm 151 Sm 93 a 152 Sm 153 Sm 154 Sm s-process path MACS-30 = 3100 ± 160 mb new cross section plus realistic s-process modelling can explain 71% of solar 152 Gd yield; missing yield provided by p-process; main uncertainty: T-dependent half-life of 151 Sm. alberto.mengoni@cern.ch

12 2. The RIB facility at Louvain-la-Neuve Production & acceleration of isobarically pure and intense low-energy radioactive ion beams specially suitable for nuclear astrophysics Intense 30 MeV proton beam CYCLONE110 CYCLONE30 I < 300 μa CYCLONE44 E: MeV/A M/Q: 4 to 14 LEDA beam line ARES RIB intensities up to pps on target angulo@cyc.ucl.ac.be

13 Experimental equipment at CRC/UC Louvain-la-Neuve 7 Be(d,p)2α (2-10) x 10 6 /s 7 Be beam CD 2 target p, α, p FC Cup (4-6) x 10 6 /s LEDA type 16 strips in θ 300 μm or 500 μm d( 18 F,pα) 15 N Solid angle: 10% of 4π angulo@cyc.ucl.ac.be

14 ARES recoil separator at CRC/UC Louvain-la-Neuve beam rejection factor: 5x x10-7 ΔE-E Detector Slits 0 1m Slits Quadrupole triplet Quadrupole doublet Wien filter CYCLONE44 Quadrupole doublet CH Target Monitors 2 Dipole magnet solid CYCLONE44 E = MeV/A, intense RIB ( pps) angulo@cyc.ucl.ac.be

15 Astrophysical activities at CRC/UC Louvain-la-Neuve (non-exhaustive...) 1. Direct measurements of fusion reactions with radioactive beams detected with ARES recoil separator e.g.: 19 Ne(p,γ) 20 Na relevant for hot-cno rp process 2. Direct measurements of fusion reactions with radioactive beams detected in kinematic coincidences (LEDA,LAMP) e.g.: 18 F(p,α) 15 O relevant for γ-astronomy on 18 F e.g.: 7 Be(d,p)2α relevant for 7 Li abundance used as a baryometer 3. Elastic-scattering reactions with radioactive beams e.g.: 7 Be(p,p) 7 Be relevant for 7 Be(p,γ) 8 B etc.

16 BBN nuclear reactions affecting 7 Li production? An interesting case: 7 Be(d,p)2α t(α,γ) 7 Li and 7 Li(p,α)α 3 He(α,γ) 7 Be(n,p) 30% angulo@cyc.ucl.ac.be

17 7 Be(d,p)2α S-factor measured at BBN energies total BBN energies p 0 +p 1 but: no solution for the 7 Li problem!

18 3. The GANIL/SPIRAL radioactive beam facility

19 The GANIL/SPIRAL-1 radioactive beam facility

20 Astrophysical activities at GANIL 1. Decay spectroscopy (β-, γ-, βn-decay) of stopped nuclei after in-flight separation Q β -values, half-lives, P n values, level schemes... e.g. nuclear structure around N=28 relevant for r-process, isotopic anomalies GANIL 2. Study of (n,γ) cross sections on unstable isotopes via HI(d,p) e.g. 40,44,46 Ar(d,p) relevant for r-process, isotopic anomalies SPIRAL 3. Study of fusion reactions via resonant elastic scattering (RES) e.g. 18 F+p 19 Na* 18 F+p, 15 O+α 19 Ne* 15 O+α relevant for hot CNO rp-process SPIRAL

21 40,44,46 Ar 11A.MeV (d,p) reactions with 40,44,46 Ar beams 8 modules MUST p CD 2 380μg.cm -2 10cm. SPEG sorlin@ganil.fr GANIL/SPIRAL 170 CATS 41,45,47 Ar 110 BEAM : ~ parallel optics (Angular aperture < 2mrad; φ = 2 cm) MUST : -Si Strip detector. -Proton impact localisation. -Proton energy measurement. - 60mm x 60mm. - X,Y resolution : 1 mm. -Intrinsic resolution : 50 KeV. CATS : -gas filled beam-tracking detector - Proton emission point. - 70mm x 70 mm. - X,Y resolution : ~0.6 mm. Identification detectors SPEG : Energy loss spectrometer : recoil ion identification (background suppression)

22 18 F(p,α) 15 O studied via 15 0+α RES 15 O beam from SPIRAL E/A = 1.74 MeV I > 10 7 /s run in April 2005 sorlin@ganil.fr

23 4. SIS/FRS at GSI as a radioactive beam facility stable and secondary beams 100 < E/A < 1500 MeV ALADIN/LAND production target SIS FRS ESR SIS FRS: high-resolution zero-degree spectrometer ALADIN: large-acceptance spectrometer ESR: 11 Tm storage ring k.suemmerer@gsi.de

24 Astrophysical activities at GSI 1. Coulomb-dissociation at relativistic energies KaoS: A + Pb -> B + p +Pb LAND: C + Pb -> D + n +Pb relevant for pp and r-, p-process 2. In-ring β-decay of stored bare nuclei e.g. bound-state β-decay of 163 Dy and 187 Re relevant for s-process and cosmo-chronometer 3. Introduction of realistic fission-fragment distributions into r-process calculations relevant for r-process

25 Coulomb-dissociation of 8 B to study 7 Be(p,γ) Coulomb dissociation of 254 A MeV 8 B in complete kinematics at FRS/KaoS at GSI Theory: P. Descouvemont's cluster model of 8 B Seattle (p,γ) data: S 17 (0) = 21.2 ±0.6 ±0.6 evb GSI-2 CD data: S 17 (0) = 20.6 ± 1.3 ± 1.5 ev b k.suemmerer@gsi.de

26 In-ring detection of bound-state β decay ( 187 Re 75+ ) stored 187 Re 75+ ions 10 8 'lifetime' 2.5 hours 187 Os 75+ β b -daughters/hour N d = λ βb <N m > 200 storage times: hours stripping off the electron of H-like 187 Os 75+ in a N 2 gas jet (10 13 p/cm 2 ) switched-on for about 2 minutes recording the bare 187 Os 76+ ions as function of storage time T 1/2 ( 187 Re 75+ ) = ( ) yr T 1/2 ( 187 Re 0+ ) = 42.5 Gyr f.bosch@gsi.de

27 Bound-state β-decay and branching points in the s-process: the case 163 Dy/ 163 Ho p process Er Ho Dy s-process at T s 30 kev: pathway determined by: neutron flux n n, n-capture cross-sections ρ e, β - decay probabilities λ s process r process branching points: for λ λ(t s ) n n for λ = λ (T s ) T s, ρ e from Dy-, Ho-, and Er- abundances and from λ βb ( 163 Dy 66+ ) = 1.72 x 10-7 s -1 at the A = 163 branching point*: T s = ( ) 10 8 K; ρ e = ( ) cm -3 *F. Käppeler et al., Ann. Rev. Nucl. Part. Sc. 48 (1998) 175 f.bosch@gsi.de

28 r-process nucleosynthesis and fission S. Wanajo fission - ν-induced fission - n-induced fission - β-delayed fission - spontaneous fission Fission plays an important role in the r-process - yields of transuranium isotopes and age of the universe - may have a strong influence on the formation of the majority of heavy nuclei due to fission recycling - r-process end point a.kelic@gsi.de

29 A- and Z-distributions of fission fragments - ν-induced fission is irrelevant for r-process progenitors in the mass range A ~ , but becomes more and more important with increasing mass number. - The calculated mass and charge distributions show pronounced peaks coming from symmetric and asymmetric fission. These peaks are in agreement with patterns observed in the r-process abundance distributions in metal-poor stars at mass numbers A ~ 90 and ~ 135. a.kelic@gsi.de

30 5. JYFL Accelerator Jyväskylä5 K130 MeV Cyclotron ECR & light-ion sources IGISOL RITU ari.s.jokinen@phys.jyu.fi

31 IGISOL floor plan Ion Guide Stopping in gas mostly 1+ Fast, universal Refractories U target proton beam He inlet Stopping volume p [mbar] 250 Neutral atom Ion V 4 10 kv 30 kv Ion Guide Technique Fission reaction Light-ion reactions Heavy-ion fusion reactions Transfer reactions Singly charged DC 40 kv Energy spread even 100 ev cooling and bunching in RFQ RFQ Laser Spectroscopy JYFLTRAP Nuclear Spectroscopy ari.s.jokinen@phys.jyu.fi

32 Astrophysical activities at JYFL/IGISOL 1. Decay spectroscopy (γ-, βp, βα-decay) of mass-separated nuclei to study level schemes/resonance strengths e.g.: 12 N β + 12 C* ααα relevant for triple-a process e.g.: 23 Al βγ/βp 23 Mg to study 22 Na(p,γ) 23 Mg 31 Cl βγ/βp 31 S to study 30 P(p,γ) 31 S relevant for nova nucleosynthesis 2. Decay spectroscopy (γ-decay, βn-decay) of mass-separated n-rich nuclei to obtain half-lives and P n values relevant for extrapolation to r-process path 3. Mass measurements in JYFLTRAP of short-lived fission products relevant for extrapolation to r-process path

33 BREAKOUT OF THE NeNa CYCLE THROUGH THE 22 Na(p,γ) 23 Mg CAPTURE REACTION STUDIED BY BETA DECAY OF 23 Al 23 Al 470 ms 24 Al 2.1 s Mg Al cycle t 1/2 = 470(30) ms Q EC = (25) MeV 5/2 + β + 22 Mg 3.9 s 23 Mg 11.3 s 24 Mg 21 Na 22.5 s 22 Na 2.6 a 23 Na Na IAS MeV 20 Ne 21 Ne 22 Ne 5/ MeV stable isotope (p, γ) 3/ Mg (β +, ν) K. Peräjärvi et al., Phys. Lett. B 492 (2000) 1

34 Beta-delayed protons and gammas observed in the β decay of 23 Al DE DE SE SE COUNTS ENERGY [kev] K. Peräjärvi et al., Phys. Lett. B 492 (2000) 1

35 6. The AGOR + BBS facility at KVI Big Bite Spectrometer (BBS): dp/p = ± 9.5% focal plane detectors: 4π coverage, particle id high resolution: FWHM 90 kev AGOR cyclotron (K=600): light and medium-heavy stable beams plus tritium beams ( 2x10 7 /s) E/A < 90 MeV/nucleon berg@kvi.nl

36 Astrophysical activities at KVI 1. Transfer reactions in inverse kinematics e.g.: p( 21 Ne,t) 19 Ne to study 15 O(a,γ) 19 Ne p( 24 Mg,t) 22 Mg to study 21 Na(p,γ) 22 Mg relevant for hot CNO rp process 2. Probing GT + strength with HI(d, 2 He) high resolution data! relevant for EC in supernova

37 Studying 15 O(a,γ) 19 Ne via p( 21 Ne,t) 19 Ne at KVI α-branching is very small: 15 O(α,γ) 19 Ne is too slow to feed the rp process

38 Studying EC on 58 Ni via 58 Ni(d, 2 He) 58 Co at KVI 58 Ni(d, 2 He) 58 Co E=85A MeV 58 Ni(n,p) 58 Co E=198 MeV 10 0 Strong influence of GT strength on calculated EC rate! berg@kvi.nl

39 Conclusions, Topics to be discussed Contributions to astrophysics from all methods available (ISOL, ISOL+postacceleration, fast fragmentation); High degree of networking! (Nuclear theory, stellar theory, and Improvements? experiment) Competitive instrumentation? (Recoil separator, Si arrays,...) Combine forces? Small-scale vs. large-scale facilities? Future developments at LSF? REX-ISOLDE, n_tof, SPIRAL-II, FAIR...

40 Special thanks to... Luis Fraile, CERN-ISOLDE; Hans Fynbo, CERN-ISOLDE/Aarhus; Alberto Mengoni, CERN-n_TOF; Carmen Angulo, CRC/UC Louvain-la-Neuve; Olivier Sorlin, GANIL; Fritz Bosch, Hans Geissel, Aleksandra Kelic, GSI; Ari Jokinen, JYFL; Ad van den Berg, KVI.