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a neutron. Application of the detailed balance theorem
would then enable the neutron capture cross section to
be determined. Since these experiments are performed
in inverse kinematics they can also be applied to radioactive
beams. This might be a promising approach to
measure neutron capture cross sections further away
from stability as is needed for the r process nucleosynthesis.
However, this requires high energy radioactive
beam facilities with high intensities like FAIR. Transfer
reactions like (d,p) reactions are a very efficient means
to measure the spectroscopic factors that are required
to determine the resonant and direct capture reaction
rates. These transfer reactions should be measured at
low energies (5-10 MeV/u) and using high radioactive
beam intensities like those provided at the SPIRAL 2
facility. Another method that is used successfully for
neutron-induced fission cross sections is the surrogate
method. So far, no successful proof of principle could
be performed for neutron capture cross sections, but it
might be an interesting additional approach.
Photonuclear measurements
Systematic studies of photon-induced reaction rates
relevant for nucleosynthesis have been carried out at
bremsstrahlung facilities located at electron accelerators
like e.g. ELBE (Dresden, Germany) and S-DALINAC
(Darmstadt, Germany) in the last decade. While (γ,n)
reactions were studied in a broad mass range only very
few (γ,α) and (γ,p) reactions have been measured so
far. The ongoing improvements at these facilities will
increase the number of accessible reactions during the
next years. In addition, cross sections have to be studied
energy-resolved to improve the reliability of the nuclear
structure input for predictions of reaction rates. Thus,
energy-resolved measurements with photons have highest
priority for the development of the field and can be
achieved using either tagged photons or Laser Compton
Backscattering (LCB) sources.
While tagged photons will be available in the astrophysically
relevant energy region in the upcoming
years at the photon tagger NEPTUN at the S-DALINAC,
Darmstadt, Germany, there is a lack of a European LCB
source. As such a photon source is also of high interest
for nuclear structure purposes it is worthwhile planning
the development of a facility outperforming the state-ofthe-art
setup of the High Intensity γ-ray Source (HIgS,
DFELL, Durham, NC, USA). This might be possible in
the framework of the Extreme Light Infrastructure ELI
that has been initiated in Europe. The centre planned
at Bucharest, Romania, is dedicated to nuclear physics
including photonuclear physics and should include a LCB
source to complete the European portfolio of photon
sources for nuclear physics purposes.
Key questions of heavy element nucleosynthesis
often correspond to studies of unstable nuclei. In that
case, photonuclear reactions can be investigated using
Coulomb dissociation in inverse kinematics at the LAND
setup at GSI, Germany, and in future at the R 3 B setup at
FAIR, Germany. The combination of results from these
experiments on exotic nuclei with high-precision data
on stable nuclei using bremsstrahlung and LCB photons
will significantly contribute to an appropriate database
for the understanding of nucleosynthesis.
Accelerator Mass Spectrometry
approaches
The use of Accelerator Mass Spectrometry (AMS) in
the astrophysical context is twofold. Firstly, AMS can
be used to perform measurements of reactions leading
to long-lived radionuclides. These complement
experiments at dedicated nuclear physics facilities or
underground laboratories, in particular for measurements
of neutron capture reactions for the s-process, proton
and α-induced reactions for various burning phases or
photodisintegration rates for the p-process. AMS is used
to quantify the long-lived reaction products following an
irradiation with neutrons, charged particles or photons.
Amongst others the experiments will be performed in
close collaboration with neutron facilities (e.g. FRANZ)
or high-intensity photon sources (e.g. S-DALINAC).
Secondly, the superb sensitivity and background
suppression can be used for detection of very minute
amounts of supernova-produced radionuclides in terrestrial
archives and to provide information on isotopic
anomalies in pre-solar grains found in meteorites. Some
of these activities are already supported within the
EUROGENESIS programme.
Currently, there are about 80 AMS facilities operational
worldwide; with more than 30 facilities
Europe has the largest concentration of AMS accelerators.
Several laboratories have programmes related
to astrophysical research with the groups in Munich
(GAMS) and Vienna (VERA) playing a leading role. It is
important that these activities receive continued support.
In particular, having at least one large tandem accelerator
(>10 MV) available for AMS is crucial for measurements
of heavier nuclei (A>50) where high isobar suppression
is necessary.
On the other hand, developments towards smaller and
simpler AMS systems (as it is pursued at ETH Zurich)
are also beneficial for astrophysical research because
these systems often allow measurements with higher
efficiencies, which is particularly crucial for the detection
of minute amounts of long-lived radionuclides in
terrestrial archives or activated materials. Additionally,
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