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Identifying key studies in nuclear astrophysics through the CARINA network

Carmen Angulo angulo@cyc.ucl.ac.be CARINA network and CRC Louvain-la-Neuve, Belgium. Identifying key studies in nuclear astrophysics through the CARINA network. The CARINA network in the I3 EURONS CARINA = Challenges and Advance Research In Nuclear Astrophysics

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Identifying key studies in nuclear astrophysics through the CARINA network

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  1. Carmen Angulo angulo@cyc.ucl.ac.be CARINA network and CRC Louvain-la-Neuve, Belgium Identifying key studies in nuclear astrophysics through the CARINA network The CARINA network in the I3 EURONS CARINA = Challenges and Advance Research In Nuclear Astrophysics I3 = Integrated Infrastructure Initiative (FP6) EURONS = EURopean Nuclear Structure EURISOL workshop ECT* Trento January 16-20, 2006

  2. Main goals of the CARINA network • To carry out mapping studies of the European situation in terms of projects, facilities and teams in order to identify the available instrumentation and human potential. • To develop the research capabilities of existing Large Scale Facilities (LSF) and of smaller laboratories and enhance involvement in the future RIB facilities. • To record the needs for new instrumentation and techniques; look for existing “solutions” in other fields. • To coordinate research efforts by defining and proposing common research goals and by encouraging new collaborations and new R&D projects. Date of beginning: 1 January 2005 Date of end: 31 December 2008 Budget: 35 k€

  3. What is the role of CARINA? • To provide coherence to the research activities in nuclear astrophysics in Europe by: • Identifying the key forefront studies • Providing guidance to laboratories • Assuring best development and usage of the facilities Who is involved in CARINA? • Representatives of the EURONS experimental LSF. • Representatives of other European laboratories involved in nuclear astrophysics that answered to the call. • CARINA is also (and mainly) intended as a forum of discussion.

  4. CARINA Tasks (I) • Task 1: Setup activity • 1.1 Four working groups have been established (January 2005): • "Theory" - nuclear and astrophysical modelsConveners: Alain Coc (CSNSM)/ Jordi José (Barcelona) • "Instrumentation" Conveners : Tom Davinson (Edinburgh)/ Giacomo de Angelis (INFN LNL) • “Link to the EURONS LSF”Conveners : Alberto Mengoni (CERN) / Klaus Sümmerer (GSI) • “Link to non-EURONS LSF labs working on nuclear astrophysics” • Conveners : Michael Heil (KFZ Karlsruhe) / Endre Somorjai (ATOMKI) • 1.2 The CARINA webpage is launched on January 2005

  5. CARINA Tasks (II) Task 2: Actions 2.1 Workshops The first CARINA workshop held on June 8-10, 2005. Co-organized by the IEEC/UPC Barcelona and the CARINA coordinator. Announced in the CARINA webpage at end of January 2005. Announced in the NuPECC website: www.nupecc.org/calendar Information sent to the coordinators of all EURONS activities. First Circular sent in February 3rd, 2005. 2.2 Report on the First workshop: November 2005.

  6. CARINA: milestones and deliverables

  7. The goal of the first workshop Perspectives in European nuclear astrophysics • Questions to be answered: • What is the European situation in terms of projects, facilities and teams? • What is the present available instrumentation and human potential? • What are the research capabilities of the existing LSF and of the other laboratories ? How to enhance involvement in the future RIB facilities? • What are the needs for new instrumentation and techniques; for existing solutions in other fields? • Does this network sound meaningful to European research ?

  8. Program of the first workshop Perspectives in European nuclear astrophysics • (39 registered) 37 participants from 10 EC countries and Associated states • Program: review talks, working group sessions (all plenary) • 5 review talks: • Astrophysical models – explosive burning (M. Hernánz, Barcelona) • Astrophysical models – quiescent burning/AGB (M. Busso, Perugia) • Nuclear models for astrophysics (P. Descouvemont, Brussels) • Experiments using RIB at European LSF (K. Sümmerer, Darmstadt) • Experiments at European non-EURONS facilities (M. Heil, Karlsruhe) • Working group sessions: short talks + round table discussions • Summary • Election of the Steering Committee

  9. Quests in Nuclear Astrophysics • Large variety of problems large variety of methods • Beams of electrons, neutrons, light and heavy ions (stable and unstable). • Energies: from ten of keV to multi-GeV. • Facilities: university and small labs accelerators, “table-top” underground labs, large-scale facilities… • Specific tools: • Big Bang nucleosynthesis, pp-chain, CNO cycle… • Recoil separators, forward magnetic spectrometers, high-efficiency gamma detectors • Explosive scenarios (hot CNO, rp process, etc…) • Low-energy, intense & pure radioactive beams (ISOL-type) • High beam energies, purity and speed of separation (fragmentation + in-flight)

  10. Facilities for Nuclear Astrophysics • Large number of small- and medium-scale facilities which are beneficial to the field (attract students, act as ‘feeders’ to large-scale facilities). • A few important reactions in quiescent burning: still to be investigated. But the scientific interest will move towards astrophysical sites involving radioactive species. • In the future, two large-scale radioactive beam facilities: • ISOL-type: EURISOL • Fragmentation: Super-FRS @ FAIR Both have nuclear astrophysics in their agenda…. but: • How muchbeam time can be devoted to nuclear astrophysics at these large and expensive facilities that cater to a very broad range of physics interest? • The long time-span until they become fully operational does matter.

  11. How to fulfil the needs in the near future? (I) • How to fulfil the needs of the European NA community, at least in the years of about 2008-2015? • CARINA proposes a three-tiered intermediate step: • To identify and to secure the long-term availability of: • Key facilities for specific experiments • Key theoretical institutes • To combine in a network these key facilities/institutes to assure the coherence of the scientific activities and to secure: • Technical know-how • Manpower

  12. How to fulfil the needs in the near future? (II) • To establish a ‘flagship’ ISOL-type facility providing: • High-intensity, high-purity light- to medium-mass radioactive beams. • Equipped with a full range of experimental tools (more on that later). • It could be established cost-efficiently at one of the existing European ISOL-facilities (or their upgrades): • CRC at Louvain-la-Neuve (Belgium) or • REX-ISOLDE (CERN) or, • SPIRAL at Caen (France) • The main constraint of this ‘flagship’ ISOL-type facility: • Sufficient financial investment • Major commitment towards the field of nuclear astrophysics

  13. Instrumentation for nuclear astrophysics • A survey of instrumentation available in present-day laboratories active in experimental nuclear astrophysics suggests the following required devices: • Gas targets(recirculation for rare gases; continuous luminosity monitoring) • A multi-stage fusion-product recoil separator(high leak-beam suppression, high rate focal plane detectors) • A high-resolution magnetic forward spectrometer(high rate focal plane detectors) • Large-area, fine-granularity solid-state detectors or telescopes (on sharing basis; standard electronics and DAQ systems) • A dedicated high-resolution, high-efficiency gamma-ray detection system The ‘flagship’ ISOL type facility must have these tools available for the nuclear astrophysics community.

  14. Theory for nuclear astrophysics • A tentative list of theoretical models of interest to nuclear astrophysics: • Shell model • Hauser – Feshbach • Microscopic models, • Indirect methods (Trojan Horse, ANC, ..) • R-matrix • … • Plus astrophysical models A tentative list of stellar processes and sites

  15. Stellar processes and sites • Hydrogen burning • pp – chains • CNO cycle • Ne-Na chain • Mg-Al chain • Big Bang • Main sequence stars • Helium burning • 3-a process, 12C(a,g)16O, • other (a,g) and (a,n) reactions • Red Giants stars • Asymptotic branch stars • Explosive burning • Hot CNO • rp – process (rapid p capture) • Novae • Supernovae • X-ray burst • Nucleosynthesis beyond Iron • s – process (slow neutron-capture) • r – process (rapid neutron capture) • p – process (p capture) • AGB stars • Supernovae II • ??

  16. Nuclear reactions at extreme conditions • Under extreme stellar conditions of T and density: any nucleus can undergo a series of light particle captures forming a nucleus far from stability (loosely bound, short b-decay lives): nuclear reactions rates ↔b-decay intrinsic rates or photodissociation (balance) • Hundreds of different reactions involving unstable nuclei may lie on the reaction path • What nuclear information is needed in the astrophysical models? • nuclear masses, • excited state properties, • decay properties and lifetimes, • electron capture rates, • neutrino and photon interaction rates, • light particle reaction rates. • But our current knowledge is very incomplete…Experimental challenge ! • Information inaccessible for many years to come (specially on the r-process path)

  17. Explosive burning - astrophysical sites • In explosive astrophysical sites such as the binary systems novae and X-ray bursters, nucleosynthesis [ up to A ~ 60 (nova) and A ~ 80 – 100 (X-ray burst) ] is thought to be provided by hydrogen and helium burning at high temperatures and densities. [J.José et al. ApJ (1999), H., Schatz et al., Phys. Rep. (1998) ] • Hydrogen and helium rich material from a companion aging main sequence star piles up onto the surface of a white dwarf (WD in nova) or neutron star (NS in X-ray burst) forming an accretion disk. • The temperature and density increase in the surface of the WD (T>108 K, r>103g/cm3) or NS (T>109 K, r>106 g/cm3) generating a sudden increase of the star luminosity. • Critical T and r values: reactions involving H and He on nuclei ranging from C to Ca releasing energy in a runaway thermonuclear explosion. Snapshots of a Classical Nova Outburst (cortesy of J. José)

  18. Identification of the key nuclei and reactions • The most important reactions can be identify by studying the sensitivity of the models. • For example, at very high T: capture rate ↔ photodissociation rate (equilibrium) • The reaction path is insensitive to individual reaction rates. • The material concentrates at the so-called ‘‘waiting-point’’ nuclei (and the most important parameters are the masses and b-decay rates). [H., Schatz et al., Phys. Rep. (1998).] • However, many individual reaction rates are of critical importance: • The statistical model can be used as an estimation, BUT : • Q-value is low for nuclei far from stability • Level-density is lower • Often, only 1 or 2 states contributing: there is no alternative to the study of the resonance properties. • Some innovative experimental techniques (ex. ANC and TH methods) to indirectly determine level information, but often direct measurement is needed.

  19. 27Si 28Si 27Al 24Al 25Al 26Al rp-process onset 21Mg 22Mg 23Mg 24Mg 25Mg 26Mg 23Na 20Na 21Na 22Na NeNa cycle breakout from HCNO 18Ne 19Ne 20Ne 21Ne 22Ne 17F 18F 19F 14O 15O 16O 17O 18O (p,) (,) (,p) HCNO 13N 14N 15N (p,) (b+) 13C 12C Reaction path: the hot CNO and beyond 30P(p,g)31S (exact path depends on given stellar conditions) heavy nuclei beyond S 19Ne(p,g)20Na 18Ne(a,p)21Na 15O(a,g)19Ne 14O(a,p)17F stable unstable

  20. Experimental Challenge • One of the main difficulty in experiments related to explosive burning is the implications of instable nuclei. hot CNO, escape to rp-process 13N (10 m), 15O (122 s), 17F (65 s), 18F (110 m), 19Ne (17 s) … r-process neutron-rich nuclei, far from stability • Experiments on reactions involved on explosive burning requiresradioactive beam production. • Methods : • ISOL • Projectile fragmentation • IN-FLIGHT

  21. Experimental quests and tools • Facilities • Accelerators and beams • Targets • Detectors • Ground-state properties • Masses, b-decay rates • Capture reactions • Resonant and non-resonant capture • Coulomb dissociation • Transfer reactions: type (p,a) and (a,p) • Resonant properties • Elastic and inelastic scattering • Transfer reactions • Fusion evaporation

  22. Capture reactions: (p,g) and (a,g) • Involved in quiescent and explosive burning • Most of the important capture reactions involving stable isotopes have been studied using intense p and a beams. • Main disadvantages of direct measurement: • Low efficiency of gamma detectors • Radioactivity of the target material • Background sources • Use inverse kinematics and detect the recoiling reaction products in recoil separators • ARES @ Louvain-la-Neuve • Daresbury Recoil Separator @ Oak Ridge • DRAGON @ TRIUMF • ERNA @ Bochum • FMA @ Argonne Nat. Lab.

  23. The ARES recoil separator • First 19Ne radioactive beam from CYC44 • Study of the 2.643 MeV level in 20Na wg≤ 15.2 eV (90% c.l.) Tough job ! M. Couder, PhD Thesis, 2004

  24. Targets • Gas cells, windowless gas targets, polyethylene foils • New alpha-implanted targets [F. Vanderbist et al., NIM (2004)] • Requirements: • Low Z substrate • Thick enough • Self-supporting • High 4He concentration • Homogeneity and uniform concentration

  25. RBS spectrum Alpha-implanted targets • 1st campaign • Test of substrate resistance during implantation (C, Al, Ni, Cu, Si, Sn): best results with Al • Study of evolution of content versus dose • 2nd campaign • Study of implantation profile : Analysis of homogeneity (ERDA) and content (RBS) • Implantation of very thing Al foils to study (a,g) resonances: 50 & 100 µg/cm2

  26. Typical spectrum of 15N+a elastic scattering. counts • R-matrix fit using: Ga = 8 keV • It does not work ! Use of alpha implanted targets • First experimental approach to 15O+a and 15N+a elastic scattering using solid alpha implanted targets • Final goal: Study of 15O(a,g)19Ne with ARES Study of a state Jp = 1/2+, Ex = 6.250 MeV state in 19F by 15N+a elastic scattering • Ga= 8 keV[Smotrich et al., PR(1961); re-analysis (R-matrix): Bardayan et al., PRC (2005)].

  27. 15N+a with alpha implanted targets Ga= 4.0 ± 0.7 keV Ga= 3.2 ± 0.7 keV

  28. Some key reactions 18F(p,a)15O • The competition between the 18F(p,a)15O and the 18F b-decay has consequences regarding a possible observation of the 511 keV g-ray from novae (ex. INTEGRAL): g-rays from novae have not been detected yet. • Many experiments…. (more recent works: see later) 17O(p,g)18F , 17O(p,a)14N • 17O (and perhaps 19F): galactic chemical evolution; it is believed that 17O on earth or in our bodies was made in novae • C, N, O elemental abundances are observed in emission spectra of nova ejecta; isotopic ratios 12C/13C and 14N/15N are observed in pre-solar grains that originated from nova explosions • Recent experiments at LENA @ NC (Iliadis, Champagne et al.); CSNSM @ Orsay (Tatischeff et al.)

  29. Some key reactions 14O(a,p)17F • The reaction is thought to play an important role in advanced stages of hydrogen burning, either as: a way of bypassing the slow positron decay of 14O (t1/2 = 70.6 s) in the hot CNO cycle or as a starting point to break out the cycle through the subsequent 17F(p,g)18Ne(a,p)21Na reactions. • Recent experiment at RIKEN; project at LLN 15O(a,g)19Ne • One of the main breakout reaction from the hot CNO cycle. • No direct measurement ever performed: • Very low cross section: very intense 15O beam needed (< 1012 pps) • Presently, 15O beam intensity is ~ 107 pps.

  30. Some key reactions 22Na(p,g)23Mg • Peak fluxes for the 1275 keV g-ray line (22Na decay) might be detectable by near future g-ray satellites (i.e. INTEGRAL) if an ONe nova explodes within a distance of less than ~ 0.5 kpc. 30P(p,g)31Si • Nuclear activity in the Si-Ca region is powered by a leakage from the NeNa-MgAl region, where the activity is confined during the early stages of the outburst. This is the main reaction that drives nuclear acitivity towards heavier species beyond S. • Uncertainties affecting 30P(p,g)31S influence Si yields (relevant for the identification of presolar nova candidate grains) and the nuclear activity beyond S (J. José, 2004)

  31. 18F+p ? 19F 19Ne The role of 18F(p,a)15O in the nova nucleosynthesis • The 18F(p,a)15O rate is largely uncertain: up to300 on the g-ray flux due to the unknown low-energy resonance strengths (A. Coc et al. A&A 2000) • Previous studies at Louvain-la-Neuve, Oak Ridge and Argonne concentrated mainly on two 19Ne states: • 7.066 MeV (3/2+) • 6.742 MeV (3/2-) • Influence of the low-energy levels? Interferences ? • 6.449 MeV (3/2+) • 6.437 MeV (1/2-) • 6.419 MeV (3/2+) • other states below threshold ? [J.S. Graulich et al. Phys. Rev. C63, 011302(R) (2001), and references therein.]

  32. The 18F(p,a)15O S-factor Need to determine the proton widths of the 3/2+and 1/2-states below 0.2 MeV

  33. 18F(d,pa)15N: an indirect way to investigate 18F(p,a)15O Experimental set up: 19Ne levels of interest • A 14 MeV 18F beam (2 x106 pps) on a CD2 target • Coincidences p (LAMP) and 15N or a (LEDA) Study theanalog levels in19Fby thetransfer reaction d(18F,p)19F(a)15N

  34. 18F(d,p)19F*(a)15Ne: results Two 3/2+ astrophysical levels isolated (but not resolved: FWHM  100 keV). Coincidence spectrum DWBA analysis  Spectroscopic factors: S(6.528) + S(6.497)  0.2

  35. present / WK82 present Coc et al. A&A 2000 T (109 MK) N. de Séréville, Ph.D Thesis, 2003. Uncertainty reduced by a factor of about 5 in the nova temperature range 18F(d,pa)15O also investigated at Oak Ridge at higher beam energies [Kozub et al., PRC (2005)] (a bit different conclusions). 15N(a,a)15N scattering data from Smotrich et al, (1961) re-analized by Bardayan et al., PRC (2005).

  36. 3 events Interference effects Between the two 3/2+ resonances (at Ecm = 38 and 665 keV) can significantly alter the rate of 18F destruction in novae. • Remaining nuclear uncertainties: • a-width for low energy resonances • Interference sign between 3/2+ states • Missing states ? A new experiment at the CYCLONE RIB facility Data from Bardayan et al 2002, resonance strength from de Séréville et al. 2003.

  37. The RIB facility at Louvain-la-Neuve Production & acceleration of isobarically pure and intense low-energy radioactive ion beams – specially suitable for nuclear astrophysics CYCLONE110 CYCLONE30 CYCLONE44 E: 0.2 - 0.8 MeV/A M/Q: 4 to 14 LEDA beam line ARES First RIB in 1989

  38. Particle detector arrays at Louvain-la-Neuve • Large area, highly segmented silicon strip detector arrays LEDA and CD-PAD: they can be used in many configurations to cover the required angular range • Developed and largely used at Louvain-la-Neuve • Use at present at many laboratories worldwide (Oak Ridge, TRIUMF, REX-ISOLDE…) “LEDA” type “CD” type 16 strips in q 300 mm or 500 mm 16 strips x 4 DSSD 50 mm or 500 mm Solid angle: 10% of4p 4 x PAD 1.5 mm Davinson et al., NIM A 2000 Ostrowski et al., NIM A 2002

  39. Experimental setup: 2 LEDA detectors in coincidence a 18F CH2 15O A new 18F(p,a) direct measurement May 17 – 25, 2005 @ Louvain-la-Neuve • nominal 18F beam energy: 13.8 MeV • beam intensity ~ 106 pps • a 70 mg/cm2 CH2 target • several energies using degraders: Al foils (of different thickness) • total efficiency (incl a-15O coinc.)  30% Also: a proposal at TRIUMF on 18F(p,a)15O (A. Laird, A. Murphy), standing by for 18F beam development.

  40. 18F beam production and acceleration at LLN 18F (T1/2 = 110 min): CYCLONE30: production 18O(p,n)18F with a intense p beam @ 30 MeV UCL / PET group: chemical extraction 45 minutes process, CH318F CYCLONE110: acceleration and mass separation 1 bunch of 18F every 2 h (0.5 to 1 Ci) (almost) free of 18O contamination • We got: • 17 bunches of 18F over 1.5 week and continuous 18O over the night

  41. nominal beam Degrader 95 mg/cm2 500 mg/cm2 670 mg/cm2 18F beam purity • Measurement at 0 degree (PIPS) • check degrader thickness • determine beam energy profile at target entrance 18O / 18F different energy loss 18O / 18F < 1%

  42. Preliminary results Objective: sign of interference between 3/2+ states 18F beam energies: 13.8, 12.6, 9.1, 7.6 MeV For c.m. energy below 0.2 MeV: beam of less than 4 MeV But the cross section is order of magnitude lower !! Beam intensities ~ 1010 – 1012 pps

  43. From nucleosynthesis calculations (cross sections) From primordial abundances observations (old objects), extrapolated to time 0 (BB) From very recent (2003) satellite observations The problem of primordial 7Li abundance Coc et al., Fields et al, … A problem of the rates of the reactions involved in SBBN ? (h = ratio of the baryon number to the photon number, equivalent to the baryonic density)

  44. DAACV (2004) Others (theory) The 12 main reactions involved in SBBN • A new BBN Compilation • R-matrix method • Statistical treatment of uncertainties Update and supersede the NACRE compilation for the reactions: Publication: P. Descouvemont, A. Adahchour, C. Angulo, A. Coc, E. Vangioni-Flam, ADNDT 88 (2004) 203-236. Website: http://pntpm3.ulb.ac.be/bigbang

  45. An interesting case: 7Be(d,p)2a 3He(a,g)7Be(n,p) ≤ 30% t(a,g)7Li and 7Li(p,a)a Other nuclear reactions affecting 7Li production?

  46. What do we know about 7Be(d,p)8Be ? No data at BBN energies! How to extrapolate?

  47. The 7Be+d reactions

  48. p, a, … Si detector Low energy protons (higher energy states in 8Be), a’s, scattered particles will be stopped in the first LEDA p Only high energetic protons (g.s., 1st excited state in 8Be) will pass through the first LEDA and stop in the second LEDA New experiment – set up 7Be beam FC Cup

  49. 7Be beam: energy and isobar contamination

  50. Proton spectra Higher energy excited states in 8Be: 40% of the counting rate 26 hours g.s. and first excited state in 8Be

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