Experimental setup Silicon Detector Radon Box (N flushing) Deuterium inlet Alpha beam Ge Detector HPGe Detector Deuterium exhaust Calorimeter Pipe Crown Lead shield - Germanium detector close to the beam line to increase the detection efficiency - Pipe to reduce the path of scattered deuterium, to minimize the d(d,n)3he reaction yield - Target length optimized - Copper removal - Silicon detector to monitor the neutron production through the d(d,p)3h reaction - Lead, Radon Box to reduce and stabilize Natural Background - Borated polyethylene envelope to reduce neutron contamination
Some Results What should we observe? A single γ-ray with Eγ = 173.8 + Ecm ± Edoppler 00 kev 80 kev P(D) = 0.3 mbar, Q(00) = 515 C, Q(80) = 5 C minimisation using Mukhamedzhanov angular distribution The shape of Beam Induced Background spectra weakly depends on the beam energy
Astrophysical S-factor 10-3 D(α,γ) 6 Li S [kev barn] 10-10 -5 Hammache 010 (Coulomb Dissociation) 10-6 BBN energies Mukhamedzhanov 011 (theory) 0.1 1 E [MeV] S( 9 kev) =.6 +1. -1.3 (stat) ±0.3 (syst) ± 0.5 (model) 10-6 kev b S(13 kev) = 3.5 +0.6-1.3 (stat) ±0.5 (syst) ± 0.5 (model) 10-6 kev b 6 Li/ 7 Li =1.5±0.3 10-5 much lower than adopted value (P.D.Serpico 00 and A.Coc 01) and value obtained from 6 Li detection in metal-poor stars (J.C.Howk 01) M.Anders et al.: Accepted for publication in PRL
LUNA 00 kv - Future program 13 C(α,n) 16 O neutron source (LUNA MV) 1 C(p,γ) 13 N and 13 C(p,γ) 1 N relative abundance of 1 C- 13 C in the deepest layers of H-rich envelopes of any star H(p,γ) 3 He H production in BBN Ne(α,γ) 6 Mg competes with Ne(α,n) 5 Mg neutron source (LUNA MV) 6 Li(p,γ) 7 Be improves the knowledge of 3 He(α,γ) 7 Be key reaction of p-p chain (LUNA MV) A bridge toward the LUNA - MV accelerator
A new accelerator underground Limits of a 00 kv accelerator Solar fusion reactions Stellar Helium and Carbon burning Neutron sources for astrophysical s-processes A new, higher energy underground accelerator is needed proposed solutions: LUNA-MV at Gran Sasso National Laboratory (Italy) CANFRANC (Spain) Felsenkeller (Germany) <-- shallow underground DIANA (formerly part of DUSEL) (United States) China South America
LUNA - MV project April 007: a Letter of Intent (LoI) was presented to the LNGS Scientific Committee (SC) containing key reactions of the He burning and neutron sources for the s-process 1 C(α,γ) 16 O 13 C(α,n) 16 O and Ne(α,n) 5 Mg (α,γ) reactions on 1,15 N and 18 O 3 He(α,γ) 7 Be on a wide energy range These reactions are relevant at higher temperatures (larger energies) than reactions belonging to the hydrogen-burning studied so far at LUNA Single ended 3.5 MV positive ion accelerator
Stellar Helium burning: 1 C(α,γ) 16 O 1 C/ 16 O abundance ratio Subsequent stellar evolution and nucleosynthesis Composition of White Dwarfs Mechanism of Supernovae Oxygen-16 σ tot [nb] 10000 1000 100 10 1 0.1 0.01 1E-3 1E- 1E-5 1E-6 E0 ~ 300 kev, σ(e0) ~ 10-8 nb 1E-7 0.0 0.5 1.0 1.5.0.5 3.0 3.5.0.5 5.0 E cm [MeV] 3α 1 C and 1 C(α,γ) 16 O Creation and Destruction of 1 C even with Accurate measurements at low and high energy extrapolation to E0 are needed
Data Relevant to 1 C(α,γ) 16 O E E1 1 C+α 16 O Complex level scheme Several 1 - and + Resonances Sub-threshold resonances dominate the S-factor at low energy Cascade transitions Direct capture + Interference effects Experimental data needed 1 C(α,γ) 16 O cross section data ground and excited states of 16 O wide range of energies 1 C(α,α) 1 C elastic scattering data 16 N β-delayed α spectrum Bound-state spectroscopy (Ex, Γ x, ) Transfer reactions To obtain the S-factor with an uncertainty < 10%
A modern experiment (Stuttgart Group) R.Kunz and M.Fey PhD Thesis Ion Beam Intensity 500 µa He + Stability Beam Induced Background EUROGAM Detectors Efficiency Background suppression Granularity GANDI Angular distribution but also: CalTech, Queens Univ., RUB Bochum, FZ Karlsruhe, and others ~ 1 data sets Targets Isotope separation Density ~. 10 18 atoms/cm Purity ( 1 C/ 13 C ~ 10 5 ) Omogeneity Standing Time
A modern experiment (some results) Ecm Ecm =.33 MeV 9.0 9.5 10.0 M.Fey PhD Thesis 00
A modern experiment (some results) Ecm? Ecm = 0.891 MeV 7.5 8.0 8.5 Limitation from Beam Induced or Natural Background? M.Fey PhD Thesis 00
A modern experiment (some results) Ecm = 1.0 MeV ϑ = 15 6 E c.m. = 0.891 MeV 8 E c.m. = 0.903 MeV ϑ = 30 ϑ = 5 ϑ = 60 0 0 30 60 90 10 150 180 6 0 0 30 60 90 10 150 180 ϑ = 75 ϑ = 90 ϑ = 110 ϑ = 110 35 30 5 0 15 10 E c.m. = 1.10 MeV 5 0 0 30 60 90 10 150 180 10 10 100 80 60 0 0 E c.m. = 1.5 MeV 0 0 30 60 90 10 150 180 ϑ = 110 ϑ = 110 ϑ = 15 ϑ = 10 8.0 8.5 9.0 E γ (MeV) bbildung C.9: Im Rahmen des Drehtisch-Experiments gemessene -Roh- 6000 5000 000 3000 000 1000 E c.m. = 09 MeV 0 0 30 60 90 10 150 180 7000 6000 5000 000 3000 E c.m. = 1 MeV 000 1000 0 0 30 60 90 10 150 180 Winkel angle ϑ Measurements at low energies are very difficult
A new measurement (wish list) Beam current Ibeam ~ 1 ma (pulsed?) Ultraclean Vacuum < 10-8 mbar BIB monitors (neutron and high resolution γ) Detection Efficiency 100 times higher (HPGe or Scintillator ball + GE monitor) Improved targets 13 C/ 1 C < 10-6 Better R-matrix and/or fitting codes
LUNA - MV project In a very low background environment such as LNGS, it is mandatory not to increase the neutron flux above its average value 13 C(α, n) 16 O α beam intensity: 00 µa Target: 13 C, 10 17 at/cm (99% 13 C enriched) Beam energy(lab) 0.8 MeV Study of the LUNA-MV neutron shielding by Monte Carlo simulations Ne(α, n) 5 Mg α beam intensity: 00 µa Target: Ne, 1 10 18 at/cm Beam energy(lab) 1.0 MeV 13 16 C(α, n) O from 1 C( α, γ ) α beam intensity: 00 µa Target: 13 C, 1 10 18 at/cm ( 13 C/ 1 C = 10-5 ) Beam energy(lab) 3.5 MeV B-node hypothesis: ruled out in September 013 Maximum neutron production rate : 000 n/s Maximum neutron energy (lab) : 5.6 MeV 16 O the estimated n-flux (Fluka & Geant simulations) will increase less than 1% of the LNGS natural flux
LUNA - MV project LUNA - MV (approved) Uterminal = 350-3500 kv Imax ~ 500 µa (on target) ΔE = 0.7 kev Beams: H +, He LUNA I (199-001) Uterminal < 50 kv LUNA II (000 - ) Uterminal = 50-00 kv Imax ~ 500 µa (on target) ΔE = 0.07 kev Beams: H +, He, ( 3 He) Hall C (south side) definitely assessed in early 01
LUNA - MV Accelerator Best shielding solution: 0 cm concrete + 0 cm water + 0 cm concrete Simulated neutron flux outside the shielding Φn ~ (0.39±0.13) 10-9 cm s -1 well below LNGS Limit Φn ~ 3.3 10-8 cm s -1
Grazie Atomki (Z. Elekes, Zs. Fülöp, Gy. Gyurky, E. Somorjai), Bochum (C. Rolfs, F. Strieder, H.P. Trautvetter), Dresden (D. Bemmerer, M. Takacs, T. Szucs), Edinburgh (M. Aliotta, C. Bruno, T. Davinson, D. A. Scott), Genova (F. Cavanna, P. Corvisiero, F. Ferraro, P. Prati), LNGS (A. Best, A. Boeltzig, A. Formicola, S. Gazzana, M. Junker, L. Leonzi), Milano (A. Guglielmetti, D. Trezzi), Napoli (G. Imbriani, A. Di Leva), Padova (C. Broggini, A. Caciolli, R. Depalo, R.M.), Roma (C. Gustavino), Teramo (O. Straniero), Torino (G. Gervino) New collaborators are welcome
Laboratori Nazionali del Gran Sasso