Towards the study of 22Ne(p,γ)23Na at LUNA in Gran Sasso

Towards the study of Ne(p,) Na at LUNA in Gran Sasso
22
23
Rosanna Depalo* for the LUNA Collaboration
*Università degli studi di Padova and INFN Padova
ASTROPHYSICAL MOTIVATION
The 22Ne(p,γ)23Na is a key reaction of the NeNa cycle of hydrogen burning.
Its cross section influences the abundance of the elements between 20Ne and 27Al in:
Shell H burning in Red Giant Branch and Asymptotic Giant Branch stars [1]
Explosive H burning in Classical Novae [2]
Ne+p may influence the 23Na production in type Ia supernovae (“standard candles”
in cosmology). Then 23Na(e-, e)23Ne decreases the electron abundance, affecting
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the 56Ni yield and the peak luminosity [3].
The reaction rate uncertainty in the astrophysically relevant energy region
reaches a factor of ~2000 because of 13 resonances of unknown strength:
Fig. 1: The NeNa cycle
EXPERIMENTAL SETUP
LUNA RANGE
The Laboratory for Underground Nuclear
Astrophysics is located at Laboratori Nazionali
del Gran Sasso (Italy) [7].
LUNA 400kV
400kV electrostatic accelerator
(50 < Eprotons < 400 keV ; Imax = 500 μA)
Windowless gas target. Natural neon (9.25% 22Ne),
or 99.9% Enriched 22Ne.
2 HPGe γ-ray detectors (high energy resolution, efficiency ~ 1%) in close geometry
+ lead and copper shield
Fig. 2: Level scheme of 23Na with resonance energies
of the 22Ne+p reaction in the center of mass system.
The levels at 8862, 8894 and 9000 keV have been
reported as tentative by J.R. Powers et al. (1971) [5]
but not observed by S.E. Hale et al. (2001) [4].
SOLID TARGET
GAS TARGET
Fig. 3: Pictures of the LUNA setup
(left), and of the accelerator ion
source (right)
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22Ne(p,γ)23
The
The Ne(p,γ)23Na
Na resonance
resonance at
at
EElab
=186keV
has
been
observed
=186keV
has
been
observed
lab
with
with 42
42 ±± 17
17 events
events in
in 12h.
12h.
MEASUREMENT STRATEGY
2076
440keV
Test run with the pre-existing 2H(α,γ)6Li experiment
setup (study of beam induced background, hints on
resonant reaction rate)
440keV
Study of temperature and pressure profile
in the target chamber
g.s.
Beam heating study (ongoing)
Study of 22Ne(p,γ)23Na resonances with 2 HPGe detectors
(planned for 2013)
Fig. 4: Peaks in the γ-ray spectrum corresponding to the
decay of the first and second excited states in 23Na.
References:
[1] N. Prantzos et al. A & A 470, 179–190 (2007)
[3] P. Podsiadlowski et al. arXiv:astro-ph/0608324 (2006)
[5] J.R. Powers et al. Phys. Rev. C 4, 2030-2046 (1971)
[7] C. Broggini et al. Annu. Rev. Nucl. Part. Sci. 60, 53-73 (2010)
[2] C. Iliadis et al. ApJSS 142, 105-137 (2002)
[4] S.E. Hale et al. Phys. Rev. C 65, 015801 (2001)
[6] C. Iliadis et al. Nucl. Phys. A 841, 1-322 (2010)
International School of Subnuclear Physics – Erice, 24/6 - 3/7/2013