Perspectives of Nuclear Physics in Europe - European Science ...

4.4 Nuclear Astrophysics
space- and ground-based astronomy instruments. In
parallel with the experimental and observational work,
theoretical advances are urgently needed on the reaction
sequences in Supernovae, both in the core region
as the collapse occurs and in the outer shells where
the outgoing shock creates novel new nucleosynthesis
networks (these comments apply equally to ccSN and
SN1a). Charged particle, photon, neutron and neutrino
induced reactions need to be understood and measured.
The next generation of radioactive beam facilities will at
last give us experimental access to the nuclei involved
in the r-process and enable us to measure these reaction
rates.
Nuclear Physics in Compact Objects: Neutron stars
are unique cosmic laboratories for finding answers to
one of the most fundamental questions of physics: what
are the ultimate constituents of matter Advances will
be linked to increasingly sophisticated measurements
coming from major new astrophysical instruments in
which European scientists are involved. The intensification
of ground-based and space-based observations as
well as the exciting prospect of detecting gravitational
waves drives the need for a better theoretical description
of these peculiar objects. At present the main activity
in this area is the development of the astrophysical
models and these are beginning to be linked to realistic
microscopic inputs. Much theoretical development in
nuclear physics is thus required over the next five years
in order to improve our understanding of dense matter
properties. Experimental measurements to check
these are rudimentary at present and the development
of activity in this area can be expected to grow in the
later part of the decade as the experimental facilities
required are developed.
Future facility developments
As a result of investment over the last decade, we are
entering an exciting period for nuclear astrophysics
experiments. Because of the wide range of different
beam species required, and the wide range of energies,
scientists require access to a wide variety of different
accelerator facilities. Because of the low cross sections
of some key reactions, the experiments often require very
long measuring periods, and thus cannot be run at the
large international laboratories where the pressure on
beamtime is high. Instead, smaller, and often dedicated,
facilities are better suited to address these measurements.
Over the last decade, careful coordination by
NuPECC and through the activities of the Integrating
Activities funded by the EC in FP6 and FP7, a complementary
network of stable beam facilities has been
developed across Europe which will provide the highly
required access. In addition, several AMS laboratories
of different size are available in Europe which can perform
complementary measurements of reactions with
long-lived radionuclide end products. That said, continuing
investment in these facilities will be required to
improve the beam range and intensity, and to provide
more sophisticated experimental setups to probe key
reactions where the yields are low or the backgrounds
high.
In addition to the stable beam facilities, construction
of the next generation of radioactive beam facilities
are now underway – fragmentation beams at FAIR and
ISOL beams at SPIRAL-2, HIE-ISOLDE and SPES. These
new beams will revolutionise our capability and allow
a concerted attempt to understand nucleosynthesis
in explosive sites where the evolution is dominated by
reactions between unstable nuclei. The timely completion
of these projects is vital to allow the exciting range
of nuclear astrophysics experiments outlined above to
begin. This next generation of facilities will enable great
advances during the next decade, but beyond that the
higher intensity, wider beam reach of EURISOL will be
required. As this EURISOL project develops it is essential
that the nuclear astrophysics community remain
fully engaged in the project to ensure that the technical
specifications of the facility remain in line with what is
needed for this field.
Europe has held a leading position in terms of photonuclear
reaction studies, but as the interest in this area
grows, there is a demand for higher intensity and better
quality beams. There is a strong case for considering the
provision of a Laser Compton Backscatter facility and
recent developments on the development of a nuclear
physics programme associated with the ELI project offer
such a possibility.
Europe has to date been well provided for in terms
of neutron beams for neutron capture studies, with a
number of active facilities and the recently upgraded
n-TOF facility at CERN. However as interest grows in the
nucleosynthesis in explosive environments like ccSN,
and in the nuclear physics dominating the structure of
neutron stars, there is a need for a new generation of
such facilities with greatly increased neutron fluxes and
better TOF measuring capability. Associated to these
studies is a need for facilities capable of producing the
quantities of radioactive nuclei required to fabricate
targets.
For novae, efforts should focus on multidimensional
models to account for the physical mechanism responsible
for mixing at the core-envelope interface, taking
advantage of the use of massive parallel supercomputers.
This should be supplemented with some key
observations intended to identify the predicted γ-ray
signatures accompanying the explosion as well as systematic
studies of the spectra (dust formation, complete
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