Presentation on theme: "Identifying key studies in nuclear astrophysics through the CARINA network Carmen Angulo CARINA network and CRC Louvain-la-Neuve,"— Presentation transcript:
Identifying key studies in nuclear astrophysics through the CARINA network Carmen Angulo CARINA network and CRC Louvain-la-Neuve, Belgium EURISOL workshop ECT* TrentoJanuary 16-20, 2006 The CARINA network in the I3 EURONS CARINA = Challenges and Advance Research In Nuclear Astrophysics I3 = Integrated Infrastructure Initiative (FP6) EURONS = EURopean Nuclear Structure
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€
Which are the EURONS LSF ? The world-class facilities, agreed by the EC, that constitute the backbones of EURONS are: CRC/UCL (B) ECT* (EUR) CERN-ISOLDE (EUR) GSI (D) GANIL (F) JYU-JYFL (FIN) INFN-LNL (I) RUG-KVI (NL) JYFL KVI CRC GANIL ISOLDE LNL GSI ECT*
What is the role of CARINA? Who is involved in 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 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.
CARINA Tasks (I) Task 1: Setup activity 1.1 Four working groups have been established (January 2005): 1."Theory" - nuclear and astrophysical models Conveners: Alain Coc (CSNSM)/ Jordi José (Barcelona) 1."Instrumentation" Conveners : Tom Davinson (Edinburgh)/ Giacomo de Angelis (INFN LNL) 1.“Link to the EURONS LSF” Conveners : Alberto Mengoni (CERN) / Klaus Sümmerer (GSI) 1.“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
CARINA Tasks (II) Task 2: Actions 2.1 Workshops The first CARINA workshop held on June 8-10, Co-organized by the IEEC/UPC Barcelona and the CARINA coordinator. Announced in the CARINA webpage at end of January Announced in the NuPECC website: Information sent to the coordinators of all EURONS activities. First Circular sent in February 3 rd, Report on the First workshop: November 2005.
CARINA: milestones and deliverables
The goal of the first workshop 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 ? Perspectives in European nuclear astrophysics
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
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)
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: FAIR Both have nuclear astrophysics in their agenda…. but: How much beam 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.
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 ? CARINA proposes a three-tiered intermediate step: 1.To identify and to secure the long-term availability of: – Key facilities for specific experiments – Key theoretical institutes 2.To combine in a network these key facilities/institutes to assure the coherence of the scientific activities and to secure: – Technical know-how – Manpower
How to fulfil the needs in the near future? (II) 3.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): I. CRC at Louvain-la-Neuve (Belgium) or II. REX-ISOLDE (CERN) or, III. SPIRAL at Caen (France) The main constraint of this ‘flagship’ ISOL-type facility: 1.Sufficient financial investment 2.Major commitment towards the field of nuclear astrophysics
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.
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
Stellar processes and sites Big Bang Main sequence stars Helium burning 3- process, 12 C( ) 16 O, other ( , ) and ( ,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 ?? Hydrogen burning pp – chains CNO cycle Ne-Na chain Mg-Al chain
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 -decay lives): nuclear reactions rates ↔ -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)
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>10 8 K, >10 3 g/cm 3 ) or NS (T>10 9 K, >10 6 g/cm 3 ) generating a sudden increase of the star luminosity. Critical T and 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)
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 -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.
Reaction path: the hot CNO and beyond unstable stable 12 C 13 N 14 N 15 O 14 O 15 N 13 C 16 O 17 O 18 O HCNO 23 Mg 21 Mg 22 Mg 25 Al 24 Al 24 Mg 25 Mg 26 Al 26 Mg 27 Al 27 Si 28 Si rp-process onset 17 F 18 F 18 Ne 20 Ne 19 Ne 21 Na 22 Na 20 Na 19 F 21 Ne 22 Ne 23 Na breakout from HCNO NeNa cycle (,)(,) (p, ) (+)(+) (p, ) ( ,p) (exact path depends on given stellar conditions) 15 O( ) 19 Ne 14 O( ,p) 17 F 19 Ne(p, ) 20 Na 18 Ne( ,p) 21 Na 30 P(p, ) 31 S heavy nuclei beyond S
Experimental Challenge One of the main difficulty in experiments related to explosive burning is the implications of instable nuclei. Experiments on reactions involved on explosive burning requires radioactive beam production. Methods : ISOL Projectile fragmentation IN-FLIGHT hot CNO, escape to rp-process 13 N (10 m), 15 O (122 s), 17 F (65 s), 18 F (110 m), 19 Ne (17 s) … r-process neutron-rich nuclei, far from stability
ISOL (Isotope Separation On Line): a radioactive beam is produced practically at rest in a thick target bombarded with a primary beam and post- accelerated. CERN Ganil, Oak Ridge National Lab TRIUMF, Vancouver Two major projects: RIA in the USA and EURISOL in Europe Projectile fragmentation: typically a very high energy beam is used and fragmented in a low Z target. From the many reaction products, the desired one is selected in mass, charge and momentum via a fragment separator and transported to the experimental area without acceleration. Darmstadt Flerov MSU Lanzhou Two major projects: GSI, RIKEN (under construction) IN-FLIGHT: a heavy ion at low energy (typically just above the Coulomb barrier) induce single neutron transfer reactions. Argonne Nat. RIKEN Texas AMUNotre Dame Radioactive beam facilities
Experimental quests and tools Facilities Accelerators and beams Targets Detectors Ground-state properties Masses, -decay rates Capture reactions Resonant and non-resonant capture Coulomb dissociation Transfer reactions: type (p, ) and ( ,p) Resonant properties Elastic and inelastic scattering Transfer reactions Fusion evaporation
13 C+p 13 N+p Cross section (in barn/sr) versus c.m. energy at lab =17º Resonant properties: the elastic scattering method in inverse kinematics With the acceleration of the first radioactive beam at Louvain-la-Neuve (1990), it was necessary to develop a technique to study in one step low-energy resonances using: Projectile: a RIB of a few pps (should be enough) Target: a proton-rich foil of very simple handling The first elastic scattering experiment in inverse kinematics with a stable and a RIB and a quantitative analysis, was performed in 1991 at Louvain-la-Neuve: “One-step energy scanning of wide low lying 1 - resonances in 13 C+p and 13 N+p scattering” Th. Delbar et al., Nucl. Phys. A542 (1992) 263. Resonance width (keV) Resonant energy (keV) 37.0 ± ± 1.0p + 13 N 33.7 ± ± 1.0p + 13 C
The method Yield (rel. units) beam recoil protons target energy (rel. units) detector system Typical spectrum for a ℓ =0 resonant state Beam important energy loss in the target spectacular changes in the recoil proton spectra Recoil protons negligible energy loss in the target sensitivity to presence of a resonant state Proton spectra information on the resonance energy, orbital momentum, and proton width Main features Inverse kinematics: large laboratory proton energy Interference effects are reflected in the spectrum shape:
The choice of the target A very thick target, that will stop the beam, can be used to obtain a general overview of a nuclei level scheme A thinner target must be used if precise information on energy, width and spin of one or of a few states are searched The target thickness must be adapted to the experimental goal the experimental conditions: beam energy, detection angle… Example: 13 C(p,p) using a 13 C beam … on a 20 m target E cm (MeV) … or on a 2.1 m target 0 20 m m SRIM2003 Energy straggling of the beam in the target: Do not swat a fly with a hammer!
On-line spectra and data analysis: (i) from raw spectra… The energy resolution is limited: the resonance widths must be larger than a few keV Above a certain large value of the width, the spectra are independent of the energy resolution For very thick targets, only the detection at small angles is appropriate Limitations protons 15 O 18 F 12 C J.S. Graulich et al., Phys. Rev. C63, (R)(2000). An example: 1 H( 18 F,p) 18 F
… to the theoretical analysis A.N. Lane and R.G. Thomas, Rev. Mod. Phys. 30 (1958) The R-matrix formalism The R-matrix R(E) The differential cross section The collision matrix U l The phase shift l An alternative parameterization to easily switch between “formal” and “experimental” parameters is presented in C. Angulo and P. Descouvemont, Phys. Rev. C61 (2000) (A generalization of this procedure is in C.R. Brune, Phys. Rev. C 66 (2002) ) The usual procedure to related these quantities is not direct Pole parameters (calculated or formal) Resonance parameters (observed or experimental) ! With the R-matrix for poles defined as:
Capture reactions: (p, ) and ( ) Involved in quiescent and explosive burning Most of the important capture reactions involving stable isotopes have been studied using intense p and 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 Louvain-la-Neuve Daresbury Recoil Oak Ridge TRIUMF Bochum Argonne Nat. Lab.
The ARES recoil separator ≤ 15.2 eV (90% c.l.) Tough job ! First 19 Ne radioactive beam from CYC44 Study of the MeV level in 20 Na M. Couder, PhD Thesis, 2004
ARES-II ( ) Improvements on the ARES beam-line CYCLONE 44 beam Installation of a beam monitoring system and an additional analyzing magnet. ARES efficiency New simulations including all beam line elements; modifications of some elements along the beam line. ARES rejection power Installation of an additional dipole magnet. Reactions: 19 Ne(p, ) 20 Na 13 N(p, ) 14 O 11 C(p, ) 12 N 15 O( ) 19 Ne 7 Be( ) 11 C
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 4 He concentration Homogeneity and uniform concentration
Alpha-implanted targets 1 st campaign Test of substrate resistance during implantation (C, Al, Ni, Cu, Si, Sn): best results with Al Study of evolution of content versus dose 2 nd campaign Study of implantation profile : Analysis of homogeneity (ERDA) and content (RBS) Implantation of very thing Al foils to study ( ) resonances: 50 & 100 µg/cm 2 RBS spectrum
Use of alpha implanted targets First experimental approach to 15 O+ and 15 N+ elastic scattering using solid alpha implanted targets Final goal: Study of 15 O( ) 19 Ne with ARES Study of a state J = 1/2 +, E x = MeV state in 19 F by 15 N+ elastic scattering = 8 keV [Smotrich et al., PR(1961); re-analysis (R-matrix): Bardayan et al., PRC (2005)]. counts R-matrix fit using: = 8 keV It does not work ! Typical spectrum of 15 N+ elastic scattering.
Some key reactions 18 F(p, ) 15 O The competition between the 18 F(p, ) 15 O and the 18 F -decay has consequences regarding a possible observation of the 511 keV -ray from novae (ex. INTEGRAL): - rays from novae have not been detected yet. Many experiments…. (more recent works: see later) 17 O(p, ) 18 F, 17 O(p, ) 14 N 17 O (and perhaps 19 F): galactic chemical evolution; it is believed that 17 O 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 12 C/ 13 C and 14 N/ 15 N are observed in pre-solar grains that originated from nova explosions Recent experiments at NC (Iliadis, Champagne et al.); Orsay (Tatischeff et al.)
Some key reactions 14 O( ,p) 17 F 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 14 O (t 1/2 = 70.6 s) in the hot CNO cycle or as a starting point to break out the cycle through the subsequent 17 F(p, ) 18 Ne( ,p) 21 Na reactions. Recent experiment at RIKEN; project at LLN 15 O( ) 19 Ne One of the main breakout reaction from the hot CNO cycle. No direct measurement ever performed: Very low cross section: very intense 15 O beam needed (< pps) Presently, 15 O beam intensity is ~ 10 7 pps.
Some key reactions 22 Na(p, ) 23 Mg Peak fluxes for the 1275 keV -ray line ( 22 Na decay) might be detectable by near future -ray satellites (i.e. INTEGRAL) if an ONe nova explodes within a distance of less than ~ 0.5 kpc. 30 P(p, ) 31 Si 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 30 P(p, ) 31 S influence Si yields (relevant for the identification of presolar nova candidate grains) and the nuclear activity beyond S (J. José, 2004)
The role of 18 F(p, ) 15 O in the nova nucleosynthesis [J.S. Graulich et al. Phys. Rev. C63, (R) (2001), and references therein.] 19 F 19 Ne 18 F+p ? Influence of the low-energy levels? Interferences ? MeV (3/2+) MeV (1/2-) MeV (3/2+) other states below threshold ? The 18 F(p, ) 15 O rate is largely uncertain: up to 300 on the -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 19 Ne states: MeV (3/2+) MeV (3/2-)
The 18 F(p, ) 15 O S-factor Need to determine the proton widths of the 3/2 + and 1/2 - states below 0.2 MeV
18 F(d,p ) 15 N: an indirect way to investigate 18 F(p, ) 15 O 19 Ne levels of interest A 14 MeV 18 F beam (2 x10 6 pps) on a CD 2 target Coincidences p (LAMP) and 15 N or (LEDA) Experimental set up: Study the analog levels in 19 F by the transfer reaction d( 18 F,p) 19 F( ) 15 N
present Coc et al. A&A 2000 T (10 9 MK) present / WK82 N. de Séréville, Ph.D Thesis, F(d,p ) 15 O also investigated at Oak Ridge at higher beam energies [Kozub et al., PRC (2005)] (a bit different conclusions). 15 N( ) 15 N scattering data from Smotrich et al, (1961) re-analized by Bardayan et al., PRC (2005). Uncertainty reduced by a factor of about 5 in the nova temperature range
3 events Interference effects Between the two 3/2+ resonances (at E cm = 38 and 665 keV) can significantly alter the rate of 18 F destruction in novae. Data from Bardayan et al 2002, resonance strength from de Séréville et al Remaining nuclear uncertainties: -width for low energy resonances Interference sign between 3/2 + states Missing states ? A new experiment at the CYCLONE RIB facility
The RIB facility at Louvain-la-Neuve Production & acceleration of isobarically pure and intense low-energy radioactive ion beams – specially suitable for nuclear astrophysics CYCLONE44 ARES LEDA beam line CYCLONE30CYCLONE110 E: MeV/A M/Q: 4 to 14
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…) Solid angle: 10% of4 “LEDA” type 16 strips in 300m or 500 m 16 strips x 4 DSSD 50 m or 500 m 4 x PAD 1.5 mm “CD” type Davinson et al., NIM A 2000Ostrowski et al., NIM A 2002
A new 18 F(p, ) direct measurement May 17 – 25, Louvain-la-Neuve Experimental setup: CH 2 18 F 15 O 2 LEDA detectors in coincidence nominal 18 F beam energy: 13.8 MeV beam intensity ~ 10 6 pps a 70 g/cm 2 CH 2 target several energies using degraders: Al foils (of different thickness) total efficiency (incl -15O coinc.) 30% Also: a proposal at TRIUMF on 18 F(p, ) 15 O (A. Laird, A. Murphy), standing by for 18 F beam development.
18 F beam production and acceleration at LLN We got: 17 bunches of 18 F over 1.5 week and continuous 18 O over the night 18 F (T 1/2 = 110 min): CYCLONE30: production 18 O(p,n) 18 F with a intense p 30 MeV UCL / PET group: chemical extraction 45 minutes process, CH 3 18 F CYCLONE110: acceleration and mass separation 1 bunch of 18 F every 2 h (0.5 to 1 Ci) (almost) free of 18 O contamination
18 F beam purity Degrader 670 g/cm g/cm 2 95 g/cm 2 nominal beam 18 O / 18 F different energy loss 18 O / 18 F < 1% Measurement at 0 degree (PIPS) check degrader thickness determine beam energy profile at target entrance
Preliminary results Objective: sign of interference between 3/2 + states 18 F 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 ~ – pps
14 O( ,p) 17 F The rate is dominated by the resonant contribution from the 1 -, 6.15 MeV state in 18 Ne, contributions from states in the energy range 7 – 8 MeV possible. 18 Ne Indirect studies: By transfer reactions (Garcia et al. 1991, Hahn et al. 1996, Park et al. 1999) By the inverse reaction 17 F(p, ) 14 O at Argonne (Harss et al. 1999, 2004) and Oak Ridge (Blackmon et al – preliminary) Contribution of the first excited state in 17 F?
14 O( ,p) 17 F: direct measurement A recent experiment at RIKEN (Notani et al. 2004) using a 43 MeV 14 O beam produced by the 14 N(p,n) 14 O reaction and a novel 4 He gas target at 30 K (ten times more density than at room temperature). Set up: Known-states New state Results:
14 O( ,p) 17 F: direct measurement at LLN A new proposal (LEDA coll.) has been accepted to study this reaction. A low-energy 14 O beam (expected intensity 5 x10 5 particles per second) to be produced using a new cyclotron configuration: CYCLONE110 to produce the beam by the 12 C( 3 He,n) 14 O reaction CYCLONE44 to accelerate the 14 O beam ARES beam line with a new LEDA chamber and a 4 He gas cell Gas cellLEDA 14 O
17 O(p, ) 14 N, 17 O(p, ) 18 F Of special interest is the branching ratio at 17 O: the probability that this nucleus is destroyed during thermonuclear burning via the (p, ) reaction as opposed to the (p, ) reaction. (p, ) and (p, ) rates are uncertain by several order of magnitude. The branching ratio (p, )/(p. ) varies by almost 5 orders of magnitude at the novae temperatures ( GK). Consequently, 17 O and 18 F abundance predictions based on the current 17 O+p reaction rates are highly uncertain. Coc et al. 2000; Iliadis et al O+p NACRE rates:
17 O+p: two recent results Observation of a new resonance at E lab,R = 190 keV in 17 O(p, ) 18 F Measured resonance strength = (1.2 ± 0.2) eV Temperature (GK) Uncertainties: Uncertainties: from a few orders of magnitude to…30% a factor 2.5 a factor 10 Important consequences in Important consequences in final abundances of CNOF isotopes 1) Experiment at LENA facility at TUNL, North Carolina
17 O+p: two recent results Observation of a new resonance at E lab,R = ±0.6 keV in 17 O(p, ) 18 F Measured resonance strength = (1.6 ± 0.2) meV Important consequences in Important consequences in nova nucleosynthesis 2) Experiment at CSNSM, Orsay Physical Review Letters, in press
The problem of primordial 7 Li abundance ( = ratio of the baryon number to the photon number, equivalent to the baryonic density) A problem of the rates of the reactions involved in SBBN ? From nucleosynthesis calculations (cross sections) From primordial abundances observations (old objects), extrapolated to time 0 (BB) From very recent (2003) satellite observations Coc et al., Fields et al, …
The 12 main reactions involved in SBBN DAACV (2004) Others (theory) Publication: P. Descouvemont, A. Adahchour, C. Angulo, A. Coc, E. Vangioni-Flam, ADNDT 88 (2004) A new BBN Compilation R-matrix method R-matrix method Statistical treatment of uncertainties Statistical treatment of uncertainties Update and supersede the NACRE compilation for the reactions: Website:
Other nuclear reactions affecting 7 Li production? t( ) 7 Li and 7 Li(p, ) 3 He( ) 7 Be(n,p) ≤ 30% An interesting case: 7 Be(d,p)2 7 Be(d,p)2
What do we know about 7 Be(d,p) 8 Be ? No data at BBN energies! How to extrapolate?
The 7 Be+d reactions
New experiment – set up 7 Be beam FC Cup Only high energetic protons (g.s., 1 st excited state in 8 Be) will pass through the first LEDA and stop in the second LEDA p Si detector p, , … Low energy protons (higher energy states in 8 Be), ’s, scattered particles will be stopped in the first LEDA
7 Be beam: energy and isobar contamination
Proton spectra g.s. and first excited state in 8 Be Higher energy excited states in 8 Be: 40% of the counting rate 26 hours
Results : astrophysical S-factor Kavanagh 1960: measurement at a lab angle of 90 O above the BBN energies Louvain-la-Neuve experiment 2004: measurement at BBN at 16 angles High energy levels (about 40% of total events) – not observed previously Angular distribution: isotropic C. Angulo et 17, Astrophysical Journal Letters 630 (2005) L105-L108 Negligible effect in BBN: 7 Li problem persists
Effective energy Integral 1 Integral 2
Conclusions - I Nuclear reactions involved in explosive astrophysics scenarios is one of the most exciting research subjects in nuclear astrophysics nowadays. Lot of effort has been and is currently dedicated to the development of: Highly intense and isobarically pure radioactive beams Specific detection systems New techniques (indirect methods, …) New facilities (recoil separators, …) Only a few cases discussed here. Many more reactions already investigated, some examples: 17 F(p, ) 18 Ne: Blackmon et al., Bardayan et al (Oak Ridge) 21 Na(p, ) 22 Mg: S. Bishop et al (TRIUMF), B. Davids et al., 2003 (KVI Groningen) 15 O( ) 19 Ne: B. Davids et al., 2003 (KVI Groningen) 22 Na(p, ) 23 Mg: D.G. Jenkins et al (Argonne) new forthcoming experiments….
Conclusions - II Large variety of problems large variety of methods Specific tools for experiments in each astrophysical scenario Energies from a few keV to several hundred of MeV High beam intensities: better than 10 6 pps and certainly up to pps in some cases. Instrumentation: recoil separators, forward magnetic spectrometers, high- efficiency gamma detectors, multi-strip particle detector systems RIB development involving physics + chemistry Low-energy, intense & pure radioactive beams (ISOL-type) High beam energies, purity and speed of separation (fragmentation + in-flight) CARINA: we are working on !!