1. Studying stars by going underground: the LUNA experiment at Gran Sasso Laboratory
Alessandra Guglielmetti
Universita’ degli Studi di Milano and
INFN, Milano, ITALY
Laboratory Underground Nuclear Astrophysics
Outline:
-Nuclear Fusion reactions in stars: why measuring their cross section?
-Why going underground to perform these experiments?
-The Luna Experiment at LNGS
- On-going measurements and future perspective: the LUNA-MV project

2. Why studying nuclear fusion reaction cross sections?
-Stars are powered by nuclear reactions
-Among the key parameters (chemical composition, opacity, etc.) to model stars, reactions cross sections play an important role
- They determine the origin of elements in the cosmos, stellar evolution and dynamic
- Many reactions ask for high precision data.

3. Element abundances in the solar system
Big Bang
Nuclear Astrophysics ambitious task is to explain the origin and relative abundance of the elements in the Universe 1 1 H H
H-burning & He-burning 4 He a a - -
elements
elements 12 12 C C 16 16 O O
Type II SN
Type II SN 20 20 Ne Ne 56 56 Fe Fe Fe Fe - -
peak
peak
Type I SN
Type I SN 40 40 Ca Ca
N=82 s -
process peak
AGB stars
N=126 s -
process peak
AGB stars
N=82
N=82 r r - -
process peak
process peak
N=126
N=126 19 F
Type II SN
Type II SN r r - -
process peak
process peak
Type II SN
Type II SN
118
118 Sn Sn
138
138 Ba Ba
208
208 Pb Pb
195
195 Pt Pt
232
232 Th Th
238
238 U U

4. Neutrino production in stars
p + p  2H + e+ + n
p + e- + p  2H + e+ + n
3He + p  4He + e+ + n
7Be + e  7Li + n
8B  8Be + e+ + n
13N  13C + e+ + n
15O  15N + e+ + n
17F  17O + e+ + n
p-p
chain
CNO
cycle
Solar neutrino puzzle: solved!
Neutrino flux from the Sun can be used to study:
Solar interior composition
Neutrino properties
ONLY if the cross sections of the involved reactions are known with enough accuracy

5. Big Bang nucleosynthesis
Production of the lightest elements (D, 3He, 4He, 7Li, 6Li) in the first minutes after the Big Bang
The general concordance between predicted and observed abundances (spanning more than 9 orders of magnitude) gives a direct probe of the Universal baryon density
CMB anysotropy measurements (WMAP, Plank satellites) gives an independent measurement of the Universal baryon density
The concordance of the two measurements has to be understood in terms of uncertainties in the BBN predictions

6. BBN reaction network He 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
Apart from 4He, uncertainties are dominated by systematic errors in the nuclear cross sections

7. Hydrogen burning 4p  4He + 2e+ + 2e + 26.73 MeV pp chain
See Caciolli talk
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

8. See poster by C. Gustavino
BBN reaction network He 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
See poster by C. Gustavino

9. Nuclear reactions in stars
Sun:
T= K
kT = 1 keV<< EC (0.5-2 MeV)
Reaction E0
3He(3He,2p)4He keV
d(p,)3He keV
14N(p,)15O keV
3He(4He,g)7Be keV

10. 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?

11. Danger in extrapolations!
Mesurements
Extrapol.
Sub-Thr
resonance
Tail of a broad
resonance
Narrow resonance
Non resonant process
Danger in extrapolations!

12. Sun Laboratory Luminosity = 2 ·1039 MeV/s
Q-value ( H burning) = MeV
Reaction rate = 1038 s-1
Laboratory
Rlab= Np Nt s e
Np = number of projectile ions ≈ 1014 pps (100 mA q=1+)
Nt = number of target atoms ≈ 1019 at/cm2
s = cross section = barn
e= efficiency ≈ 100% for charged particles
1% for gamma rays
Rlab ≈ counts/year

13. Rlab > Bbeam induced + Benv + Bcosmic
Bbeam induced : reactions with impurities in the target
reactions on beam collimators/apertures
Benv : natural radioactivity mainly from U and Th chains
Bcosmic : mainly muons

14. Cross section measurement requirements
3MeV < Eg < 8MeV:
0.5 Counts/s
3MeV < Eg < 8MeV
Counts/s
GOING
UNDERGROUND
HpGe 
E<3MeVpassive shielding for environmental background radiation Pb Cu
underground passive shielding is more effective since μ flux,that create secondary γ’s in the shield, is suppressed

15. (1400 m rock shielding  4000 m w.e.)
Laboratory for Underground
Nuclear Astrophysics
LUNA site
LNGS
(1400 m rock shielding  4000 m w.e.)
LUNA MV
(2012->...)
LUNA 1
( )
50 kV
LUNA 2
(2000…)
400 kV
Radiation
LNGS/surface
Muons
Neutrons
10-6
10-3

16. Still three reactions to be measured to be completed by 2015
LUNA 400 kV program
reaction
Q-value (MeV)
17O(p,g)18F
17O(p,a)14N
5.6
1.2
18O(p,g)19F
18O(p,a)15N
8.0
4.0
23Na(p,g)24Mg
11.7
22Ne(p,g)23Na
8.8
D(,)6Li
1.47
completed
just started
just started
completed
Still three reactions to be measured to be completed by 2015

17. (a,g) reactions on 14,15N and 18O
LUNA MV Project
April 2007: 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:
12C(a,g)16O
13C(a,n)16O
22Ne(a,n)25Mg
(a,g) reactions on 14,15N and 18O
These reactions are relevant at higher temperatures (larger energies) than reactions belonging to the hydrogen-burning studied so far at LUNA
Higher energy machine 3.5 MV single ended positive ion accelerator

18. Stellar Helium burning in Red Giant Stars
12C(,)16O – Holy Grail of Nuclear Astrophysics
Stellar Helium burning in Red Giant Stars
the He burning is ignited on the 4He and 14N ashes of the preceding hydrogen burning phase (pp and CNO)
relevant questions:
Energy production and time scale
of Helium burning:
4He(2,)12C(,)16O(,)20Ne
Neutron sources for s process:
14N(,)18F(+)18O(,)22Ne(,n)
22Ne(,)
Consequences
late stellar evolution
composition of C/O White dwarfs
Supernova type I explosion
Supernova type II nucleosynthesis
Oxygen-16

19. Element abundances in the solar system
Big Bang
Nuclear Astrophysics ambitious task is to explain the origin and relative abundance of the elements in the Universe 1 1 H H
H-burning & He-burning 4 He a a - -
elements
elements 12 12 C C 16 16 O O
Type II SN
Type II SN 20 20 Ne Ne 56 56 Fe Fe Fe Fe - -
peak
peak
Type I SN
Type I SN 40 40 Ca Ca
N=82 s -
process peak
AGB stars
N=126 s -
process peak
AGB stars
N=82
N=82 r r - -
process peak
process peak
N=126
N=126 19 F
Type II SN
Type II SN r r - -
process peak
process peak
Type II SN
Type II SN
118
118 Sn Sn
138
138 Ba Ba
208
208 Pb Pb
195
195 Pt Pt
232
232 Th Th
238
238 U U
n source reactions: 13C(a,n)16O and 22Ne(a,n)25Mg

20. A suitable place inside LNGS has been found (Node B), far away from other experiments. A real feasibility study started!

21. LNGS is a low background laboratory: a shielding solution has been developed and validated by Monte Carlo simulations
Just-outside the wall the n-flux is less than 1% of the LNGS natural flux!

22. The Premium Project LUNA MV submitted to the Italian Research Ministry
Year 1
Year 2
Year 3
Year 4
Year 5
Preparation of the site at LNGS (structures, plants, radiation shielding, safety systems).
Definition of the technical parameters of the ion accelerator, start of the tender and issue of the supply order
Design of beam lines for solid and gaseous targets . Purchase and construction of needed equipment and materials Design of detectors and data acquisition systems.
Purchase and construction of the required hardware and software.
Installation of the ion accelerator. Construction of the beam lines. Development of detection and data acquisition systems
Set-up and calibration of the accelerator, beam lines, detectors. Running of test experiments.
First experiment at the gas target beam line (measurement of the cross section of the 3He(a,γ)7Be reaction over a wide energy range). First experiment at the solid target beam line (determination of the contamination of titanium nanoparticles)

23. SUBMITTED! FINANCED! Year 1 Year 2 Year 3 Year 4 Year 5
Site preparation
(505)
Ion accelerator
(2000)
Shielding
(300)
accelerator beam
line (750)
beam line to the
gas target (320)
solid target (255)
γ ray detectors (450)
charged particle detectors (50)
electronics and data
acquisition (150)
mobility (120)
general expenses (450)
Post Docs (150)
PHDs (247,5)
Mobility (120)
Research grants (50)
Research grants
(50)
Tot = 2805
2942,5
170
120
Year 1
Year 2
Year 3
Year 4
Year 5
Site preparation
(505)
Ion accelerator
(2000)
Shielding
(300)
accelerator beam
line (750)
beam line to the
gas target (320)
solid target (255)
γ ray detectors (450)
charged particle detectors (50)
electronics and data
acquisition (150)
mobility (120)
general expenses (450)
Post Docs (150)
PHDs (247,5)
Mobility (120)
Research grants (50)
Research grants
(50)
Tot = 2805
2942,5
170
120
SUBMITTED!
FINANCED!

24. More recent activities
Executive project for site preparation tender
Characteristics of the requested HDPE (5%B) panels tender
Characteristics of the requested Boron Carbide for the shielding
tender
Characteristics of the accelerator tender

25. THE LUNA COLLABORATION
Laboratori Nazionali del Gran Sasso A.Formicola, M.Junker
Helmoltz-Zentrum Dresden-Rossendorf, Germany M. Anders, D. Bemmerer, Z. Elekes
INFN, Padova, Italy C. Broggini, A. Caciolli, R. De Palo, R. Menegazzo, C. Rossi Alvarez
INFN, Roma 1, Italy
C. Gustavino
Institute of Nuclear Research (ATOMKI), Debrecen, Hungary Zs.Fülöp, Gy. Gyurky, E.Somorjai, T. Szucs
Osservatorio Astronomico di Collurania, Teramo, and INFN, Napoli, Italy O. Straniero
Ruhr-Universität Bochum, Bochum, Germany C.Rolfs, F.Strieder, H.P.Trautvetter
Università di Genova and INFN, Genova, Italy F. Cavanna, P.Corvisiero, P.Prati
Università di Milano and INFN, Milano, Italy C. Bruno, A.Guglielmetti, D. Trezzi
Università di Napoli ''Federico II'', and INFN, Napoli, Italy A.Di Leva, G.Imbriani
Università di Torino and INFN, Torino, Italy G.Gervino
University of Edinburgh
M. Aliotta, T. Davinson, D. Scott