1. status and perspectives
Laboratory Underground Nuclear Astrophysics
LUNA & LUNA-MV
status and perspectives

2. The importance of going underground…
Sun:
kT = 1 keV
EC ≈ MeV
E0 ≈ 5-30 keV
for reactions of H burning
kT but also E0 << EC !!
Cross sections in the range of pb-fb at stellar energies
with typical laboratory conditions reaction rate R can be as low as few events per month

3. Background reduction – HPGe detectors - gamma
Cross section measurement requirem-ents
Overground
3MeV < Eg < 8MeV
0.5 Counts/s
Counts/s
Underground  
E<3MeVpassive shielding for environmental bck Pb Cu
Secondary gammas created by m interactions are reduced
underground passive shielding is more effective!

4. Laboratory for Underground
Nuclear Astrophysics
LUNA site
From an idea of E. Bellotti, G. Fiorentini & C. Rolfs
LUNA MV
(2015->...)
LUNA 1
( )
50 kV
LUNA 2
(2000…)
400 kV
Radiation
LNGS/surface
Muons
Neutrons
10-6
10-3
LNGS (1400 m rock shielding  4000 m w.e.)

5. LUNA 400kV accelerator E beam  50 – 400 keV
I max  500 A protons I max  250 A alphas
Energy spread  70 eV Long term stability  5eV/h

6. Hydrogen burning at LUNA
4p  4He + 2e+ + 2e MeV
p + p  d + e+ + ne
d + p  3He + g
3He +3He  a + 2p
3He +4He  7Be + g
7Be+e- 7Li + g +ne
7Be + p  8B + g
7Li + p  a + a
8B 2a + e++ ne
84.7 %
13.8 %
13.78 %
0.02 %
pp chain

7. BBN reaction network at LUNAHe 3 4 Be 7 Li H D p n 2 1 8 9 6 11 12 10 5 13
1. n p + e- + n
p + n  D + g
D + p  3He + g
D + D  3He + n
D + D  3H + p
3H + D  4He + n
3H + 4H  7Li + g
3He + n  3H + p
3He + D  4He + p
3He + 4He  7Be + g
7Li + p  4He + 4He
7Be + n  7Li + p
4He + D  6Li + g

8. LUNA 400 kV new program 2016-2019: a bridge toward LUNA MV
13C(a,n)16O – neutron source (LUNA MV)
12C(p,g)13N and 13C(p,g)14N – relative abundance of 12C-13C in the deepest layers of H-rich envelopes of any star
2H(p,g)3He – 2H production in BBN (feasibility test already performed)
22Ne(a,g)26Mg – competes with 22Ne(a,n)25Mg neutron source (LUNA MV)
6Li(p,g)7Be – improves the knowledge of 3He(a,g)7Be key reaction of p-p chain (LUNA MV)

9. 13C(a,n)16O experimental status of the art
Heil 2008
Big uncertainties in the R-matrix extrapolations. Presence of subthreshold resonances.
A low background environment is mandatory for any new study

11. LUNA MV project
LUNA MV accelerator will be installed in the south part
of Hall C of LNGS laboratory (OPERA location)
Provisionary dimensions of the hall: 27x11x5 m3
OPERA decommissioning started in Jan Should be finished by October 2016

12. LUNA MV Project- building and accelerator
Funded by the Italian Research Ministry as a “premium project” with 5 Meuro
The shielding should guarantee a neutron flux of the order of 1% of the LNGS neutron flux just outside it. Different configurations are under consideration

13. LUNA MV Project- Timeline
Accelerator tender:
Intense H+, 4He+, 12C+ e 12C++ beams in the energy range: 350 keV-3.5 MeV. One beam line with all necessary elements also included.
Contract signed by 12/2015.
Total budget about 3.9 Meuro: from LUNA MV Premium projects (total 5.3 Meuro)

14. LUNA MV- scientific program (2019 )
13C(a,n)16O: enriched 13C solid target. Neutron detector
Data taking at LUNA 400 kV in 2018.
22Ne(a,n)25Mg: enriched 22Ne gas target. Neutron detector.
12C(a,g)16O: 12C solid target depleted in 13C and alpha beam or a jet gas target and 12C beam.
12C+12C: solid state target. Gamma and particle detectors
Possible commissioning measurement: 14N(p,g)15O. Solid target with known characteristics and production process. Already available HPGe detectors.
High scientific interest for revised data covering a wide energy range (400 keV- 3.5 MeV)
Produce scientific results of high impact but reduced risk immediately after commissioning phase.

15. LUNA MV- scientific program
A full proposal will be submitted to LNGS-SC and to INFN within summer 2016.
In the next months a final «Call for Collaborators» will be open.
Next fall LUNA will start working on the new proposal

16. The LUNA collaboration
A. Best, A. Boeltzig*, A. Formicola, S. Gazzana, I. Kochanek, M. Junker, L. Leonzi | INFN LNGS /*GSSI, Italy
D. Bemmerer, M. Takacs, T. Szucs | HZDR Dresden, Germany
C. Broggini, A. Caciolli, R. Depalo, R. Menegazzo, D. Piatti | Università di Padova and INFN Padova, Italy
C. Gustavino | INFN Roma1, Italy
Z. Elekes, Zs. Fülöp, Gy. Gyurky| MTA-ATOMKI Debrecen, Hungary
O. Straniero | INAF Osservatorio Astronomico di Collurania, Teramo, Italy
F. Cavanna, P. Corvisiero, F. Ferraro, P. Prati, S. Zavatarelli | Università di Genova and INFN Genova, Italy
A. Guglielmetti, D. Trezzi | Università di Milano and INFN Milano, Italy
A. Di Leva, G. Imbriani, | Università di Napoli and INFN Napoli, Italy
G. Gervino | Università di Torino and INFN Torino, Italy
M. Aliotta, C. Bruno, T. Davinson | University of Edinburgh, United Kingdom
G.F. Ciani, G. D’Erasmo, E.M. Fiore, V. Mossa, F. Pantaleo, V. Paticchio, R. Perrino, L. Schiavulli, A. Valentini| Università di Bari and INFN Bari, Italy

17. The LUNA group in Genova
Paolo Prati, 70%, Resp. Naz. e Spokesperson
Sandra Zavatarelli, 20%
Francesca Cavanna, 100% - AR
Federico Ferraro, 100% - PhD
Piero Corvisiero, 100% (0% !) – Primo LUNA SP (ed inventore della sigla…)
Richieste:
Travel ≈ 30 k€
Costruzione Apparati ≈ 30 k€
Manutenzione ≈ 60 k€ (di cui 50 sub judice per modifica HPGe-ULB

18. 2H(a,g)6Li measurement - motivation
The two «Lithium problems»
BBN 7Li predictions are a factor 2-4 higher than observations: a nuclear physics solution is highly improbable (e.g 3He(4He,g)7Be meas. at LUNA)
The amount of 6Li predicted by BBN is about 3 oom lower than the observed one in metal poor stars (debated but still «true» for a few metal poor stars)
BBN predicts 6Li/7Li = 2 * 10-5 much below the detected levels of about 6Li/7Li= 5 * 10-2
Necessary to constrain nuclear physics input 2H(a,g)6Li

19. 2H(a,g)6Li measurement - setup
Strong beam induced background due to:
Rutherford scattering of 4He beam on 2H target
2H(d,n)3He reaction
Inelastic neutron scattering on different materials (Cu, Pb, Ge,…) g background in the 2H(a,g)6Li RoI
The beam induced background weakly depends on the beam energy

20. 2H(a,g)6Li measurement- g spectra
An irradiation at one given beam energy can be used as a background monitor for an irradiation at a different beam energy, if the two ROIs do not overlap
Natural background subtracted
400 keV data (grey filled)
280 keV data (red empty) rescaled to take into account the weak energy dependence of the beam induced background

21. 2H(a,g)6Li measurement - available data
Upper limits (indirect meas)
No data in the BBN energy range!

22. 2H(a,g)6Li measurement- results
M. Anders et al.,
Phys. Rev. Lett. 113 (2014)
New LUNA data
From the new data on the 2H(a,g)6Li reaction: 6Li/7Li = (1.5 ± 0.3) * 10-5
Standard BBN production as a possible explanation for the reported 6Li detections is ruled out. “Non standard” physics solutions?

23. 17O(p,g)18F measurement – available data
State of the art before the LUNA measurement:
Rolfs et al., 1973, prompt g
SDC ≈ 9 keV b for Ecm= keV
Fox et al., 2005, prompt g
discovered 183 keV resonance
wg = (1.2±0.2) 10-6 eV
SDC = E E2
Chafa et al., 2007, activation
wg = (2.2±0.4) 10-6 eV
SDC = E E2
larger than Fox by more than 50%
Newton et al., 2010, prompt g
SDC measured for Ecm = keV
Calculated SDC(E) = 4.6 keV b (±23%)
Hager et al.(DRAGON), 2012, recoil separator Ecm = keV
SDC higher than Newton and Fox. No flat dependence.

24. 17O(p,g)18F measurement - setup
183 keV resonance and direct capture component for E= keV measured with prompt gammas and activation Gamow window for Novae region explored with the highest precision to-date
Enriched (70%) 17O targets on tantalum backings (anodization process)

25. 17O(p,g)18F measurement - spectra
183 keV resonance: wg=1.67±0.12 meV (weighted average of prompt and activation)
Several new transitions identified and branching ratios determined

26. Background reduction - Si detectors - alpha
Underground+Pb vs. Overground: factor ~10-15 reduction in the range 200 keV MeV
PRELIMINARY

27. 1991: First Background Test in LNGS SSB Detector thickness = 2 mm

28. 17O(p,g)18F measurement - motivation
17O+p is very important for hydrogen burning in different stellar environments:
- Red giants
- Massive stars
- AGB
- Novae
- light nuclei (17O/18O/18F …) abundances
- observation of 18F g-ray signal (b+ decay, annihilation with e-, 511 keV gamma)
Classical novae T= GK => EGamow = 100 – 260 keV
For 17O(p,γ)18F: resonance at Ep = 183 keV and non resonant contribution

29. 17O(p,g)18F measurement - results
The new reaction rate allows to calculate abundances of 18O, 18F, 19F and 15N using nova models with 10% precision
D. Scott et al., Phys. Rev. Lett. 109 (2012)
A. Di Leva et al., Phys. Rev. C 89 (2014)

30. On going activities at LUNA 400 kV:
17O(p,a)14N and 18O(p,a)15N reactions
In AGB stars ( T= GK )
CNO cycle takes place in H burning shell
Measured 17O/16O and 18O/16O abundances in pre-solar grain give information on AGB surface composition
Information on mixing processes if cross sections are well known

31. On going activities at LUNA 400 kV:
17O(p,a)14N and 18O(p,a)15N reactions
18O(p,a)15N
17O(p,a)14N
Q = 4 MeV
Two narrow resonances at 95 and 152 keV
Main goals:
rescan excitation function
95 keV resonance (strength and energy)
Measure below 70 keV
Q = 1.2 MeV
Two narrow resonances at 70 and 193 keV
Main goal:
70 keV resonance

32. On going activities at LUNA 400 kV:
17O(p,a)14N and 18O(p,a)15N reactions
proton beam from LUNA 400 kV
enriched 17O or 18O targets
8 silicon detectors
foils of Al Mylar to stop backscattered protons low alpha particle energy ( keV for 17O(p,a)14N reaction)
Silicon detector
Solid target position

33. The 17O(p,a)14N reaction: 70 keV res
PRELIMINARY
Very preliminary analysis favours a larger strength value compared with literature
If confirmed, it would have an astrophysical impact
Analysis is still ongoing

34. The 18O(p,a)15N reaction PRELIMINARY
Data taking completed. Data analysis on going
PRELIMINARY
152 keV resonance
334 keV resonance
216 keV resonance
In agreement with previous data
Might improve precision on resonance energy and strength
95 keV resonance strength: precision about 10% (20-30% literature)
energy determined with 0.5 keV precision (2.2 keV literature)
60 keV measured with about 20% statistical uncertainty

35. On going activities at LUNA 400 kV: 22Ne(p,g)23Na reaction
NeNa cycle of H burning. Active in astrophysical novae
Impact on the abundances of: 22Ne (factor 100) 23Na (factor 7) 24Mg (factor 70)

36. The 22Ne(p,g)23Na reaction
The “red” resonances have been directly observed for the first time
For the resonances at 71, 105 and 215 keV in “black” an upper limit has been found 2 oom or more lower with respect to previous direct measurements
On going BGO phase (71 and res. plus DC from 200 to 360 keV)

37. Now “on beam”: the 23Na(p,g)24Mg and 18O(p,g)19F reactions - AGB nucleosynthesis
NeNa Cycle
20Ne
23Na
(p,g)
(p,a)
22Na
22Ne
e+n
3 yr
21Ne
21Na
22 s
19F
(p,
24Mg
27Al
(p,
27Si
e+
4 s
26Al
26Mg
6 s
25Mg
25Al
7 s
MgAl Cycle
Goal of 23Na(p,g)24Mg measurement: 144 keV resonance and DC component.
BGO detector first. HPGe if feasible
Goal of 18O(p,g)19F measurement: 95 keV resonance and DC component. BGO detector first, HPGe if feasible