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4.3 Nuclear Structure and Dynamics
Figure 13. Schematic view of the R 3 B setup comprising the
calorimeter CALIFA, a target-recoil tracking system, a largeacceptance
super-conducting dipole, the neutron detector
NeuLAND, as well as tracking systems for charged particles
and heavy ions.
When combined with efficient gamma-ray arrays, these
spectrometers will play an important role in studies of
elastic and inelastic scattering and various transfer processes,
especially with RIBs.
The study of extremely neutron–rich nuclei makes
high-granularity and high-efficiency neutron detector
arrays mandatory. Examples are the NEDA and neutron-
TOF arrays for SPIRAL2, optimised for the detection
of reaction and decay neutrons, respectively, and the
equivalent DESPEC instrumentation for NuSTAR.
A prominent example for the next generation experiments
for kinematically complete measurements of
reactions with relativistic RIB is the R 3 B setup at the
Super-FRS at FAIR. Important contributions for nuclear
structure research are expected from studies of unbound
systems, knock-out and quasi-free scattering and
multipole responses of nuclei as a function of N/Z, which
all belong to the R 3 B physics programme.
Experiments at storage rings
A worldwide unique feature of NuSTAR at FAIR is the
storage-ring complex, which provides a special nuclearphysics
programme with relativistic highly-charged
radioactive nuclei. Precision experiments with cooled
and uncooled beams allow properties of ground and isomeric
states (masses, lifetimes, decay properties) to be
investigated. Pure isomeric beams can be produced for
half-life studies, which are impossible with conventional
methods. Atomic spectra and nuclear properties can be
studied in the laboratory under conditions, which prevail
in stellar plasmas: highly-charged ions exhibit new decay
modes and altered decay properties, which affect the
modelling of stellar nucleosynthesis. Reaction studies
with internal targets and hadronic and leptonic probes
will be the goal of the EXL and ELISe experiments.
Traps and lasers
Ion traps have recently played a key role in extending
accurate mass measurements towards the production
limits of exotic nuclei. The resulting systematics are
crucial for astrophysics and fundamental interactions
research, but will also be combined with other spectroscopic
data for studies in changes of nuclear structure.
Ion traps will also be used to deliver pure species of short
living exotic nuclei for spectroscopic studies as recently
shown with JYFLTRAP at IGISOL. A unique combination
of ion-traps called MATS is designed for mass measurements
and decay studies at FAIR-NuSTAR.
Developments to extend laser spectroscopy methods
to accurate measurements of the charge radius, spin,
magnetic dipole moment and also the electric quadrupole
moment of exotic isotopes are going on within the
LaSpec project at NUSTAR and at the DESIR facility, a
comprehensive facility for decay spectroscopy, laser
spectroscopy, mass spectrometry and ion trapping
techniques, designed for low-energy beams generated
by SPIRAL and SPIRAL2.
During the last decade, laser resonance ionization
has developed into a mature technique, playing a key
role in the production of pure RIBs at ISOL facilities. The
technique has advanced and developed to a point where
it is the most favoured production mechanism of RIBs
at ISOLDE, where it is used also for producing isomeric
beams. Isomeric beams open up a new degree of freedom
in e.g. reaction or decay studies, and will be one of
the key developments in the future ISOL facilities.
Technological challenges
A common feature of the above mentioned detection
systems is the very large number of electronics channels,
which can in some cases exceed 10 4 . The nuclear
structure community has therefore started to develop
highly integrated front-end electronics based on application
specific integrated circuits (ASIC), Contrary to
high-energy physics these need to address a number of
conflicting requirements, e.g. large dynamic ranges, low
intrinsic noise for high resolution spectroscopy etc.
Future in-beam studies and also focal-plane studies
of medium-heavy and light nuclei with intense RIB and
especially stable-ion beams are often limited by the
counting rates of the associated detectors. Therefore, in
addition to various types of highly segmented detectors,
novel digital electronics and triggerless data acquisition
systems need to be developed further.
In experiments synthesising and studying the rarest
nuclei, such as very heavy elements, limits are set by the
large power deposition in the target and by the resolving
126 | Perspectives of Nuclear Physics in Europe – NuPECC Long Range Plan 2010