ALNA- Accelerator Laboratory for Nuclear

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ALNA- Accelerator Laboratory for
Nuclear Astrophysics Underground
Heide Costantini University of Notre Dame, IN,
USA INFN, Genova, Italy
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Outline

• Nuclear astrophysics
• - main reactions
• - experimental problems

• LUNA
• - an example of experimental nuclear
  astrophysics laboratory UNDERGROUND

• ALNA
• goal
• methods
• experimental techniques

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the abundance of the elements in the Universe
elements are produced inside stars during their
life
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Hydrogen burning
produces energy for most of the life of the stars
4p ? 4He 2e 2?e 26.73 MeV
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Helium burning
4He
4He
Triple ?
12C(?,?)16O
16O(?,?)20Ne
16O
12C
20Ne
4He
Two questions remain relevant Energy production
and timescale 4He(2?,?)12C(?,?)16O(?,?)20Ne Neu
tron production for weak s-process 14N(?,?)18F(?
?)18O(?,?)22Ne(?,n)
22Ne(?,?) Neutron production for fast
s-process 13C(?,n)
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?(E) S(E)exp(-2??) /E
S(E) E?(E)exp(2??)
2?? 31.29 Z1 Z2 (?/E)0.5
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Cross section measurement requirements
Rlab gt Bcosm Benv Bbeam induced
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LUNA site
Laboratory for Underground Nuclear Astrophysics
LNGS (shielding ? 4000 m w.e.)
Radiation LNGS/surface
Muons Neutrons Photons 10-6 10-3 10-1
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Measurements _at_ LUNA
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LUNA II
U 50 400 kV I ? 500 ?A for protons I ? 250 ?A
for alphas
Energy spread ? 70eV Long term stability 5 eV/h
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Q 7.3 MeV
14N(p,?)15O
15O
BGO summing crystal
Spectrum 70 keV
?t 49.12 days
Q 927?7 C
Reaction Rate 10.95 ? 0.83 c/d Background rate
21.14 ? 0.75 c/d
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LUNA main results
3He(3He,2p)4He
14N(p,?)15O

• Lowest energy 2cts/month
• Lowest cross section 0.02 pbarn
• Background lt 410-2 cts/d in ROI

Low cosmic background
High beam current
full advantage Underground lab
High efficiency detector
Pure gas target
Event identification
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Goal at ALNA

• systematic study of reactions relevant for the
  understanding of He-burning and C-burning in red
  giants, AGB stars and late evolutionary stages

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1st phase
Accelerator Requirements
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1st phase
Detector facility requirements
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Facility requirements

• Depth shielding
  ? 4000 (mwe)
• Space 15X10X5 (m3)
  accelerator
• 15x10x5 (m3) (target room 1st phase)
• 15X20X5 (m3) (target room 2nd
  phase)
• Electrical power 50 kW (1st phase)
• 200 kW (2nd phase)
• Additional facilities machine shop
• power supply
• low level counting
• DI water system
• compressed air
• LN2
• 5 ton crane in target area

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Contributors and collaborators
A. Champagne University of North
Carolina R. Clark LBNL M.
Couder University of Notre
Dame M. Cromaz LBNL A. Garcia
University of Washington J.
Görres University of Notre
Dame U. Greife Colorado
School of Mines C. Iliadis
University of North Carolina D. Leitner
LBNL P. Parker Yale
University K. Snover
University of Washington P. Vetter
LBNL M Wiescher University of Notre Dame
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Neutron sources 13C(?,n)16O, 22Ne(?,n)25Mg,
17O(?,n)
Slow neutron capture reactions (s-process) are
responsible for the origin of approximately 50
of isotopes above iron
Principal proposed site are AGB stars and stellar
He and C- burning in massive stars
The s-process rate depends on initial
n-abundance ? reaction rate of n-sources reactions
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LUNAs accelerators
50 kV LUNAI
3He(3He,2p)4He
d(p,?)3He
d(3He,p)4He