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

1. Executive Summary
from the few-body systems, the range of application of
ab initio many-body methods to describe properties of
nuclei with increasing numbers of nucleons.
Attempts are being made to establish the limits of
nuclear existence with respect to disintegration by fission
(quest for superheavy elements) and with respect
to the binding of individual nucleons (drip lines and dilute
halo systems). Important nuclear reaction probabilities
are determined for fields as diverse as astrophysics and
the transmutation of nuclear waste. It is estimated that
more than 8 000 nuclei may remain bound, with only
about a quarter of these having been identified. Nuclear
behaviour is expected to be significantly altered in the
yet unexplored regions. Some of the key questions today
are:
• How can we describe the rich variety of low-energy
structure and reactions of nuclei in terms of the fundamental
interactions between individual particles
• How can we predict the evolution of nuclear collective
and single-particle properties as functions of mass,
iso-spin, angular momentum and temperature
• How do regular and simple patterns emerge in the
structure of complex nuclei
• What are the key variables governing the dynamics
between colliding composite systems of nucleons
A central challenge in present-day nuclear structure
physics is the understanding of exotic nuclear states
and exotic nuclei very far from the line of stability, the
latter comprising the small number of naturally occurring
stable nuclear isotopes. Such exotic nuclei play an
important role in the sequence of reactions that form the
heavier stable nuclei that can be found on our planet.
Significant efforts are being taken to make inroads into
this unchartered territory by developing new techniques
and accelerator facilities to produce beams of unstable
isotopes, so-called rare isotope or radioactive beams
(RIBs, e.g. at SPIRAL2, FAIR and on the more distant
horizon at the proposed EURISOL facility). In this connection,
nuclear reactions play a major role and therefore
further developments of reaction theory and connections
with nuclear structure, possibly microscopic and ab
initio, should be an important aspect for future investigations.
The realisation of this programme requires the availability
of both RIB and stable-ion beam (SIB) facilities,
along with the development of new experimental techniques
and instrumentation. New dedicated facilities
delivering high intensity heavy ion beams are needed
for the synthesis of new super-heavy elements and to
investigate their properties. Several smaller accelerator
facilities are also essential for specific experiments
requiring long beam times or for developing and testing
of new instruments. This will ensure that experiments are
carried out on many fronts by a large user community,
and, very importantly, will provide training to the nextgeneration
researchers.
Many of the most important experimental results on
nuclear structure and reactions with RIBs originated from
the European first generation of RIB facilities at GANIL
(France), GSI (Germany) and ISOLDE (CERN). There are
two complementary methods to produce RIBs: in-flight
separation and the ISOL approach. The next generation
RIB facilities in Europe build on these principles. The
major in-flight project is FAIR (NUSTAR) at GSI, the major
ISOL project is SPIRAL 2 at GANIL, both of which are
on the ESFRI list.
An upgrade of ISOLDE to HIE-ISOLDE has very
recently been endorsed by the CERN Research Board.
SPIRAL2, HIE-ISOLDE and the SPES- facility at LNL are
due to come on-line in 2013-2015. SPIRAL2 will deliver
the most intense beams of neutron-rich nuclei produced
by secondary fast-neutron induced fission, as well as
products of other reactions induced by high-intensity
heavy ion beams. HIE-ISOLDE will provide proton-rich
and neutron-rich products of reactions induced by 1.4
GeV protons, giving for example a unique source of
exotic heavy nuclei produced by spallation reactions.
SPES will produce beams of fission products following
direct proton bombardment of uranium targets. These
facilities will together produce accelerated beams of
a wide and complementary range of radionuclides as
demanded by the future science programme. They will
be intermediate-stage ISOL projects that bridge the
technological gap between present day facilities and
EURISOL, the next generation ISOL facility for Europe
for 2020 and beyond.
Advanced instrumentation plays a major role in the
future programmes. Novel radioactive and cryogenic
targets are required for many studies. Combined with
the Super Fragment Separator (Super-FRS) at FAIR, R3B
is a next generation device, which will provide kinematically
complete reaction data with relativistic RIBs. The
Advanced GAmma Tracking Array, AGATA, will represent
a breakthrough in instrumentation for gamma-ray
spectroscopy. This will be the first 4π gamma-ray spectrometer
built solely from Ge detectors and allowing
gamma-ray tracking. The technique will undoubtedly
find extensive practical applications in other domains,
such as medical imaging. A wide range of magnetic
spectrometer systems at European accelerator laboratories
will be ready to be combined with AGATA. It
will be a key instrument in RIB experiments at FAIR-
NUSTAR, SPIRAL2 and SPES. The availability of ion
traps of increased sensitivity will also play a key role
when extending accurate mass measurements towards
the production limits of exotic nuclei.
14 | Perspectives of Nuclear Physics in Europe – NuPECC Long Range Plan 2010