1. György Gyürky Institute of Nuclear Research (Atomki) Debrecen, Hungary
Experimental nuclear astrophysics: studying the stars in the laboratory
György Gyürky
Institute of Nuclear Research (Atomki)
Debrecen, Hungary
Szilárd Leó Colloquium, BME, 10 October 2017

2. Research at ATOMKI http://www.atomki.hu Research topics:
Experimental and theoretical nuclear physics
Atomic physics
Ion beam analysis
Environmental science
Solid state physics
etc…
Main facilities:
K20 cyclotron
1 MV and 5MV Van de Graaff
(new) Tandetron
Accelerator Mass Spectrometry
Microprobe
Target laboratory
ECR ion source
Electron spectrometer
SIMS/SNMS surface analysis device
Radiochemistry lab …

3. Research activities of the nuclear astrophysics group of ATOMKI
Underground experiments:
low cross section measurements
(LUNA collaboration)
Experiments for the
astrophysical p-process
Study of the electron
screening effect
Half-life measurements
relevant to astrophysics
RIB experiments
relevant to astrophysics
7Be isotope production
for nuclear astrophysics
experiment
Application of the
Trojan Horse
indirect method
etc...

4. Energy generation of stars
A nap belsejében
sunrise
sunset
Nuclear reactions
Main sequence stars: hydrogen burning
Conversion of 4 protons into one 4He
pp-chain(s)
Inside the Sun

5. pp-chains of hydrogen burning

6. The original sin: stars have time
Sun
A supernova
15 million K
1.3 keV (Coulomb barrier: keV)
 << barn
10 billion years
~ 1 billion K
~100 keV
 < 10-9 barn
~ 1 s

7. Relevant energies in nuclear astrophysics
tunneling probability
Maxwell-Boltzmann
distribution

8. Danger of extrapolation
Raw experimental data
K.W. McVoy et al., Nucl. Phys. A542 (1992) 295

9. Danger of extrapolation
Theoretical model

10. Danger of extrapolation

11. Danger of extrapolation
Different parameters

12. Danger of extrapolation
Different theoretical description

13. Astrophysical example: 3He + 3He 4He +2p

14. Astrophysical S-factor?
Barrier penetration  steeply (exponentially) dropping cross section
S-factor: smoother energy dependence
Contains nuclear physics
Easier to extrapolate
S(E) = E·(E)·exp(2)
2 = Z1 Z2 (/E)0.5

15. Astrophysical example: 3He + 3He 4He +2p
5 orders of magnitude !!!

16. Experimental difficulties
Low cross section  low count rate
High intensity beams
Long measurements
Background reduction
Cosmic rays are difficult to avoid  let’s go underground

17. LUNA: watching the stars from the deep
Laboratori
Nazionali
del Gran Sasso
1400 m depth
LUNA collaboration:
Laboratory for Underground
Nuclear Astrophysics
" Some people are so crazy that they actually venture into deep mines to observe
the stars in the sky ".
(Naturalis Historia - Plinio, ad)

18. Firts measurements directly at solar energies
LUNA 1998
1 event in 2 weeks!!!

19. LUNA experiments 1992-2017 23Na(p,)24Mg 17O(p,)18F 14N(p,)15O
7Be(p,)8B
d(,)6Li
25Mg(p,)26Al
3He(,)7Be
22Ne(p,)23Na
3He(d,p)4He
15N(p,)16O
17O(p,)14N
d(p,)3He

20. One of the most recent LUNA results
17O(p,)14N cross section measurement
„A long-standing puzzle on the origin of stardust recovered from meteorites
has finally been solved thanks to the better understanding of nuclear reactions
happening in stars producing such dust grains.”

21. “Composition” of the Universe
Fe-Ni
Big bang, H, He, (7Li)
Stellar burning stages, C-Fe
Heavy elements: s-, r-, p-processes, Fe-U
Cosmic ray, Li, Be, B

22. Synthesis of heavy elements
p-process
s-process
r-process

23. p-process p-isotopes r-process r-isotopes Zr Y Sr (n,g) Rb Kr Br (b-)
Neutron number
Proton number Zr Y Sr
(n,g) Rb
p-isotopes Kr Br
(b-) Se As
r-process
(b+) Ge Ga Zn
r-isotopes Cu Ni Co Fe

24. p-nuclei (p-nuts): the unknown Universe
78Kr
84Sr
92Nb
92,94Mo
96,98Ru
102Pd
106,108Cd
113In
112,114Sn
120Te
124,126Xe
130,132Ba
138La
136,138Ce
144,146Sm
156,158Dy
162Er
168Yb
174Hf
180Ta
180W
184Os
190Pt
196Hg
mainly even-even nuclei
0.1-1% isotopic abundance
mass number s -
process r p 10 2 1 3 4 5
abundance (Si = 106) -1 -2 -3 -4 -5

25. The synthesis of p-isotopes
Secondary process
Gamma-induced /mainly (,n)/ reactions on s- and r-process seed isotopes (-process)
High temperature needed: supernova explosions
(,n)
108Sn
109Sn
110Sn
111Sn
112Sn
113Sn
114Sn
115Sn
116Sn
(,)
(,p)
106Cd
108Cd 25 25 25

26. Courtesy: S. Goriely

27. p-process reaction network
~ 2000 isotopes ~ reactions
Mainly (,n), (,), (,p) reaction and beta decays
The models are
not able to
reproduce the
observed
p-isotope
abundances
I. Dillmann et al., J. Phys. G 35 (2008) Mo 27

28. Contradicting theory, no experiment

29. Experiments in Debrecen
ERC Starting Grant
„Nuclear reaction studies
relevant to the astrophysical
p-process nucleosynthesis”
Experiments in Debrecen
Alpha-induced reactions: 5-15 MeV
 Cyclotron
Proton-induced reactions: 1-4 MeV
 Tandetron, (Van de Graaff)

30. Testing theoretical calculations

31. Direct influence on p-process networks
(,)
(,)
(,)
(,p)
(,p)
(,p)
(,n)
(,n)
(,n)
106Cd
108Cd
110Cd
old
Main reaction path
based on the
reaction rates
new
secondary paths
T = 2.0·109 K

32. Outlook 1: Racing with astronomers
CNO cycle
Solar composition problem: contradiction between
Helioseismology (high precision)
Solar model, supported by neutrino detection (high precision)
14N(p,)15O
More precise reaction cross sections needed!

33. Outlook 2: Studying unstable nuclei
Many astrophysical processes involve short-lived radioactive nuclei
Radioactive Ion Beam facilities needed

34. Thank you for
your attention!