TRIAC Progress Report - KEK

1. Introduction
Following the successful re-acceleration of short-lived radioactive ion beams
(RIBs) from the isotope separator on-line (ISOL) in the early 1990s, many ISOL-based
RIB facilities have been constructed over the world, and now are operating for various
research fields such as in nuclear physics, nuclear astrophysics, and materials science.
The low-energy RIBs, energy variable and with a high purity and good energy
resolution, are very effective not only for the detailed spectroscopic studies on nuclear
structure using nuclear reactions but also for studies on the structural and dynamical
properties of the bulk of materials.
At the Tandem accelerator facility of JAEA-Tokai, an ISOL-based radioactive ion
beam facility, TRIAC-Tokai Radioactive Ion Accelerator Complex - is operational since
the November of 2005. In the facility, short-lived radioactive ions produced by proton
or heavy ion induced nuclear reactions, after being mass-separated by the JAEA-ISOL,
can be accelerated up to the energy necessary for experiments. The energy is variable in
the range from 0.14 to 1.09 MeV/nucleon, which is the energy region available at the
first stage of the complete version of the TRIAC.
The present energy range of RIBs available at the TRIAC is suitable for direct
measurements for light ion induced nuclear reaction rates involved in the
nucleosynthesis at the explosive stage of the stellar evolution of massive stars as well as
in the early universe. The low energy RIBs can be also incorporated by implantation
into materials of interest whose properties can be probed with an unprecedented
sensitivity by using various nuclear spectroscopy techniques.
Since the first public operation, 50 days per year, in maximum, has been allowed
for experiments, including 10-day operation for the development of the RIB generation
and the acceleration at the TRIAC. The experimental proposals were carefully reviewed,
once a year, by the program advisory committee (PAC).
In the following, we first introduce the scientific activities for the developments of
RIB at the TRIAC. The summary of the experiments performed so far will follow.
2. Developments of the beam generation and acceleration at the TRIAC
The developments have been concentrated for the production and acceleration of
heavy (medium-mass) neutron-rich radioactive ion beams with high efficiency. The
followings are included in this section; (1) the development of target / ion source of the
JAEA-ISOL for effective production and ionization of uranium fission fragments, (2)
the development for charge breeding the singly charged ions from the ISOL, (3) the
development of post-accelerators for CW operation, upgrading acceleration energy, and
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