Misura della reazione 3He(4He,?)7Be a LUNA

1
LUNA at LNGS
Alessandra Guglielmetti Universita degli Studi
di Milano and INFN, Milano, ITALY

• Outline
• -Nuclear Fusion reactions in stars
• -Why going underground
• -The Luna Experiment
• -Future perspective

2
Hydrogen burning
Produces energy for most of the life of the stars
4p ? 4He 2e 2?e 26.73 MeV
3
Nuclear reactions in stars
Sun T 1.5 107 K kT 1 keVltlt EC (0.5-2 MeV)
Reaction E0
3He(3He,2p)4He 21 keV
d(p,?)3He 6 keV
14N(p,?)15O 27 keV
3He(4He,g)7Be 22 keV
4
Cross section and astrophysical S factor
Astrophysical factor
Gamow energy region
Gamow factor EG
Cross section of the order of pb!
S factor can be extrapolated to zero energy but
if resonances are present?
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Mesurements
Extrapol.
Sub-Thr resonance
Tail of a broad resonance
Narrow resonance
Non resonant process
Danger in extrapolations!
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Sun Luminosity (irradiated energy per time)
2 1039 MeV/s Q-value (energy for each reaction)
26.73 MeV ? Reaction rate 1038 s-1
Laboratory Rlab ??Ip?Nav/A
e 10 IP mA ? mg/cm2
pb lt s lt nb
event/month lt Rlab lt event/day ? Underground
Laboratory
7
Cross section measurement requirements
Rlab gt Bcosm Benv Bbeam induced
8
LUNA site
Laboratory for Underground Nuclear Astrophysics
LNGS (shielding ? 4000 m w.e.)
Radiation LNGS/surface
Muons Neutrons 10-6 10-3
9
Laboratory for Underground Nuclear Astrophysics
400 kV 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
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LUNA "non solar phase" 2006-ongoing

(p,g) reactions on Nitrogen, Oxygen, Neon,
Sodium and Magnesium isotopes belonging to CNO,
NeNa and MgAl cycles of Hydrogen
burning Important for second generation stars
with temperature and mass higher than those of
our Sun Seeds of the reactions already
present Higher Coulomb barrier these cycles are
unimportant for energy generation but essential
for nucleosynthesis of elements with Agt20
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D(4He,g)6Li
6Li detected in metal poor stars is unexpectedly
large compared to BBN predictions. D(4He,g)6Li is
the main reaction for 6Li production No direct
measurements for Ecmlt650 keV Theoretical
calculations for the S-factor differ by more than
one order of magnitude
12
data taking concluded
reaction Q-value (MeV) Gamow energy (keV) Lowest meas. Energy (keV) LUNA limit
15N(p,g)16O 12.13 10-300 130 50
17O(p,g)18F 5.6 35-260 300 65
18O(p,g)19F 8.0 50-200 143 89
23Na(p,g)24Mg 11.7 100-200 240 138
22Ne(p,g)23Na 8.8 50-300 250 68
D(?,?)6Li 1.47 50-300 700(direct) 50(indirect) 50
CNO cycle
In progress
Ne-Na cycle
BBN
In progress
proposal approved by LNGS SC in 2007
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LOI to LNGS for a new accelerator for He-burning
key reactions
3.5 MeV accelerator
14
Recoil mass separator approach
Aa?Cg
Cn
a
A
detection
A/Cgt1015
?
A
detection
separation
coincidence
- low induced background - high detection
efficiency - measurement of stot - low background
g-ray spectra
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European Recoil-separator for Nuclear
Astrophysics
ion source
tandem accelerator
recoil focusing
beam preparation
ion beam purification velocity and
momentum filter

• detection
• setup

magnetic quadrupole multiplets
ion beam emittance control
4He gas target
Wien filter (velocity)
Wien filter (velocity)
60 magnet (momentum)
recoils separation
TOF/DE-E detector
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ERNA experimental program

Hydrogen burning and neutrino flux from
8B 3He(a,g)7Be? measured in Bochum 7Be(p,g)8B
Helium burning and synthesis of Oxygen and
Fluorine 12C(a,g)16O measured in Bochum down to
2 MeV CM 14N(a,g)18F(b)18O 15N(a,g)19F
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LUNA COLLABORATION
Laboratori Nazionali del Gran Sasso, INFN,
ASSERGI A.Formicola, C.Gustavino, M.Junker
Forschungszentrum Dresden-Rossendorf, GermanyD.
Bemmerer, M.Marta INFN, Padova, ItalyC.
Broggini, A. Caciolli, M. Erhard, R.Menegazzo, C.
Rossi Alvarez Institute of Nuclear Research
(ATOMKI), Debrecen, HungaryZ.Elekes, Zs.Fülöp,
Gy. Gyurky, E.Somorjai Osservatorio Astronomico
di Collurania, Teramo, and INFN, Napoli, ItalyO.
Straniero Ruhr-Universität Bochum, Bochum,
GermanyC.Rolfs, F.Strieder, H.P.Trautvetter
Seconda Università di Napoli, Caserta, and INFN,
Napoli, ItalyF.Terrasi Università di Genova and
INFN, Genova, ItalyF. Confortola, P.Corvisiero,
H. Costantini, A. Lemut, P.Prati Università di
Milano and INFN, Milano, ItalyV. Capogrosso,
A.Guglielmetti, C. Mazzocchi Università di
Napoli ''Federico II'', and INFN, Napoli,
ItalyG.Imbriani,B. Limata, V.Roca Università di
Torino and INFN, Torino, ItalyG.Gervino
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ERNA COLLABORATION
INFN, Napoli, ItalyM. De Cesare, N. De Cesare,
A. Di Leva, A. D'Onofrio, L. Gialanella, G.
Imbriani, B. Limata, M. Romano, D. Schuermann,
F.Terrasi, S. Cristallo, L. Piersanti INFN,
Napoli, ItalyM. Busso, R. Guandalini, M. Nucci,
S. Palmerini. A. Salterelli Ruhr-Universität
Bochum, Bochum, GermanyD. Rogalla, C.Rolfs,
F.Strieder Institute of Nuclear Research
(ATOMKI), Debrecen, Hungary University of
Connecticut, USA CNRS Orsay, France
University of Jerusalem, Israel