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ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
Stable ion beams for nuclear astrophysics: Where do we stand ?
S. V. HarissopulosTandem Accelerator Laboratory, Institute of Nuclear Physics, NCSR “Demokritos”, Athens, GR
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
Nuclear Astrophysics …
studies aiming at understanding HOW
nuclear processes influence
astrophysical phenomena.
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
Astrophysical environments Nuclear processes
Novae, supernovae,X-ray bursts
AGB stars,supernovae II,Neutrons stars
Red giant stars, stars of the
Asymptotic branch
Big Bang(primordial nucleosynthesis)
Hydrogen burning proton-proton chain, CNO cycle, Ne-Na cycle, Mg-Al cycle
Explosive burningHot CNO cycleRapid proton capture (rp process)
Nucleosynthesis beyond ironSlow neutron captures (s-process)Rapid neutron captures (r-process) photodisintegrations and proton captures (p-
process)
Helium burning3a-process, 12C(a,γ)16OOther (a,γ) and (a,n) reactions
Reactions between the lightest elementsp, d, He, Be, Li
Advance burning stagesReactions of C, O, N, Ne, Si…
Super giant stars,Wolf-Rayet stars andPre-supernovae
Main sequence (e.g. Sun)
Cou
rtes
y: C
. An
gulo
(H
abil
itat
ion
thes
is, 2
006)
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
Major “stellar beams”:Major “stellar beams”: p, n, α, d, 3He, C, O ..
also γ !Targets Targets :: any nucleus (stable or unstable)
Energies :Energies : depending on the temperature of the relevant stellar environment !
(from ≈106 K up to ≈5x109 K !!!)=> cm-energies vary from 5 keV to 15
MeV
Cross between 0.1 μb and 100 mb, BUTSections :Sections : sometimes very very low … (≈ 1 fb !!!)
Typical Typical between 1 week and 1 month, beam beam however there are reactions requiring times :times : even years to be studied !!! OFTEN: DEMAND FOR VERY ACCURATE DATA (below 5%
error !!!)
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
Gamow peaks and windows : the astrophysically relevant energies
charged-particle induced reactions
neutron-induced reactions
3/2
0 2/bkTE
2
224
22 2
pt
G
ZZeEb
kTEkTE
E /3exp3
160
0
reactionbarrie
r(MeV)
E0
(keV)
T (K)
p + p (sun)
0.55 5.91.5×1
07
+ 12C (red giants)
300 561.5×1
08
12C + 12C (massive
stars)10.44 1500
≈ 1×109
p + 74Se (p
process)7.9 2800
≈ 3×109
Eo ≈ kT ∆En = 20 ÷ 500 keV
photon-induced
reactions
(γ,n)
(γ,α)
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
S factors and reaction rates: the most wanted data …
E1
nr(E) = exp(-2) S(E)
S factornon-nuclear term (s-waves only)
<v> =
0
S(E) exp dE 3/2
1/2
kT1
πμ8
12
1/2
EE
kTE G
reaction rate : reactions/sec/cm3
E0
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
Some typical uncertainties due to extrapolations
E0
200 %
Large uncertainties exist for many other key reactions, where the low energy limit was determined so far by beam-induced background.
CNO cycle reactions (T=2 × 107 K)
C. Angulo (Hab. thesis, 2006)
A. Aprahamian et al., Prog. Part. Nucl. Phys. 54, 535 (2005)
Uncertainties due to:
• Cosmic background
• Beam-induced bgd.
• Obsolete “tools”
Underground labs
Properly equipped high-current stable-beam labs
Inverse kinematics
Bochum data, T. Spillane et al, PRL 98, 122501 (2007)
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
LUNA : descending deep down to Gamow regions !
Cou
rtes
y: C
. An
gulo
(H
abil
itat
ion
thes
is, 2
006)
Sun’s center T=1.5 × 107 K
Big Bang T=0.5 × 109
K
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
Nucleosynthesis along the table of isotopes
39Y
28Ni
20Ca
8O
Fe
pp chain
CNO cycle
NeNa cycle
Si burning
s process r process
powered by neutrons (n,) / -
rp
proc
ess
powered by protons (p,) / +
100 yr 108 n/cm3 T=(0.1-0.4)×109 K
1 sec 1020 n/cm3 T =(1.8-3.3)×109 K
s process: M<M๏ (AGB stars, red giants...)
explosive nucleosynthesis
MgAl cycle
Novae, X-ray bursters…
up to Sn
>104 g/cm3 T(1-3)×109 K
r process: ? (supernovae, neutron stars)
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
Pathways for heavy-element nucleosynthesis
-
+
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
p-process reaction network
“seed “ abundances
s process
p-nuclei abundances
p process
reaction network
more than 20000 (,n), (,p), (,), n-, p-, -captures, -
decays, e-captures HAUSER-FESHBACH THEORY
Optical Model Potentials - Nuclear Level Densities γ-ray strength functions
(32≤Z≤83 , 36≤N≤131)
NEED FOR GLOBAL MODELS OF OMP, NLD, …
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
r:= <>max. / <>min.
M. Arnould and S. Goriely, Phys. Rep. 384, 1
(2003)
Impact of nuclear physics uncertainties on p-nuclei abundances
n captures
p captures
α captures
A≈100
A≈180
obtained with 14 different sets of nuclear ingredients (OMP, NLD, …) in HF calculations.
P. Demetriou et. al, Nucl. Phys. A 707, 253
(2002)
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
S factors and reaction rates: the most wanted data …
We also need to study
β decay properties (GT strengths, half-lives)
fission (of key importance, especially for the r process)
GDR and pygmy resonances
Nuclear masses and binding energies
Screening potentials
………..
Not only reaction rates are vital for nuclear astrophysics !
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
Some views …
• RIB facilities can certainly provide the tools for interesting nuclear astrophysics studies (main topic : r process). For many astrophysical questions, RIBs have to comparable to stable ones, at least in terms of intensity.
• The necessary beam-times are in most of the cases time consuming. As such, nuclear astrophysics experiments have less chances of success in PACs.
• Reaction studies in inverse kinematics can certainly provide a solution to the problem of the beam-induced background. This, however, requires certain exp. conditions, like intense beams, state-of-the art separators and target optimization and development.
• Some “old-fashioned” direct measurements like capture reactions, cannot completely be replaced by inverse kinematics studies due to beam current limitations !!!
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
Some views …
• Resonance physics put certain conditions to beam characteristics. A very good energy resolution is a must. Excitation function measurements require systems capable of undergoing energy changes within reasonable times. Therefore, cyclotrons and LINACs can sucessfully be used for certain applications only. VdG accelerators and especially TANDEMS are still the best tools for “standard-type” nuclear astrophysics.
• LUNA has decisively contributed to our understanding of stellar evolution. Underground labs have still a bright future.
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
Some views …
Indirect methodsoften model-dependent BUT very useful and
challenging
• Coulomb dissociation
• Trojan-Horse method
• Asymptotic Normalization Coefficients
need also stable beams !!!
Accelerators for nuclear astrophysics
ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec. 14-15, 2007
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