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For nuclear astrophysics applications it is essential to
further push the isospin frontier and to reach very n-rich
isotopes of r-process elements. While mass measurements
at present facilities barely touch the r-process
path, the intensity gain of the next-generation facilities
SPIRAL2, FAIR and EURISOL will allow to entry into this
terra incognita. This will also contribute towards answering
the question, whether and if so, to what extent, the
re-cycling of fissioning superheavy r-nuclei contributes
to the abundances of medium-heavy elements.
Figure 10. Two-neutron separation energies for even-N
isotones. Filled symbols are extracted from recent direct mass
measurements and the open symbols are based on the Atomic
Mass Evaluation. The energy difference between N=50 and N=52
isotones, corresponding to a two-neutron gap across N=50,
reveals a lowering trend till germanium followed by an indication
of persisting N=50 shell gap.
the first hints of structural changes, such as onsets of
deformation, nucleon pairing, proton-neutron interaction
strengths and symmetry effects.
Instruments and future directions
for direct mass measurements
The knowledge of nuclear masses has developed rapidly
in recent years. Various methods have been implemented
including ion traps, storage rings and time-of-flight spectrometers.
They are adapted to the various production
and separation methods of exotic nuclei, including superheavy
elements and reach highest sensitivity (single-ion
detection), highest selectivity (isomer separation), subkeV
precision and measurement times down to ~10 ms.
Setups and programmes for direct mass measurements
are important pillars of almost all existing RIB facilities in
Europe, thus contribute to their efficient and full exploitation.
Of particular importance is the development hybrid
systems, which combine stopping in gas cells after
in-flight separation. With this universal approach, lowenergy
and high-purity beams from fragmentation, fission
or fusion-evaporation reactions can be produced with
high phase-space density, thus combining the advantages
of ISOL and in-flight methods.
Tests of fundamental symmetries such as the CVC
hypothesis or the unitarity of the CKM matrix requires
ultimate accuracy, which is also needed for QED tests,
electronic binding energy measurements and for the
neutrino-mass determination from the mass difference
of 3 H and 3 He.
4.3.8 Facilities and
Instrumentation
Accelerator facilities
The ambitious future plans of nuclear structure research
discussed in the previous chapters rely on the availability
of complementary RIB and stable-ion beam facilities.
The advent of the fi rst generation of RIB facilities
has already opened up a new era in probing nuclei at
and beyond the limits of stability and in accessing new
regions of the nuclear chart. The last decade has seen
many important experimental results in nuclear structure
and dynamics originating from the first generation
European RIB facilities at GANIL, GSI and ISOLDE. The
two complementary methods of producing RIB, in-flight
separation and ISOL approach, combined with different
post-processing of the radioactive nuclei, will form the
pillars of the RIB facilities network in Europe.
The major next generation in-fl ight RIB facility in
Europe is the FAIR-NuSTAR facility, which is based on
the production of fragments from GeV/u beams and their
separation in the Super-FRS. First RIBs from the Super-
FRS are expected in 2016. FAIR and the ISOL facility
SPIRAL2 at GANIL are the nuclear physics projects on
the current ESFRI Roadmap. SPIRAL2 together with the
HIE-ISOLDE project, recently endorsed by the CERN
Research Board, and the SPES facility at LNL are due
to come on-line in 2013-2015. They are complementary
intermediate stage projects to bridge the technological
gap between present day facilities and the ultimate ISOL
facility EURISOL. During the last decade an extensive
R&D programme and a design study have been carried
out for EURISOL. A preparatory phase could start within
the next 5 years, and construction could be achieved
by 2025.
The scientific programme of NuSTAR and EURISOL
will cover all major topics relevant for modern nuclear
structure and dynamics research. For specific and very
Perspectives of Nuclear Physics in Europe – NuPECC Long Range Plan 2010 | 123