TRIAC Progress Report - KEK

3. Experiments at the TRIAC
Since the first public operation of the TRIAC, 50 days of operation per year, in
maximum, has been allowed for experiments, including the operation for 10 days for the
development of the RIB generation and acceleration at the TRIAC. The experimental
proposals were carefully reviewed, once a year, by the program advisory committee
(PAC). As listed in Table 3-1, 15 proposals have been approved and, among them, 13
proposals have been already performed. Two remaining proposals (KJ02 and KJ03)
have been already scheduled to be performed soon. There were 3 additional proposals
only using ISOL beams without reacceleration by post-accelerators.
The approved proposals are grouped according to relevant research field and
respectively summarized as followings: nuclear astrophysics (RNB-K01, K05, J01,
KJ03 and KJ04), nuclear and fundamental physics (RNB-K02/03, K04, and K08), and
materials science (RNB-K06, K07, J02/03, KJ01/02). The experiments using RIBs
without re-acceleration are also briefly described at the end.
3-1. Nuclear astrophysics
In recent decades, nuclear reactions involving the unstable nucleus 8 Li have
attracted considerable attention among nuclear physicists since they are considered to
influence largely the synthesis of heavy elements in neutron-rich high-temperature
environments. Such environments in the temperature of T9 = 1-3 (in unit of 10 9 K) could
happen, for example, in the early stage of supernova explosion and/or in the early
universe of inhomogeneous Big-Bang model. Continuous efforts have been made to
experimentally determine the relevant reaction rates at energies below the Coulomb
barrier. The low-energy 8 Li beam available at the TRIAC provides unique opportunities
to measure directly the relevant cross sections in the energy regime of astrophysical
interest.
The RNB-K01 (Spokesperson: H. Ishiyama (KEK) and T. Hashimoto (JAEA),
Collaboration (Institution (number of collaborators)): KEK (9), JAEA (8), Osaka
Electro-comm. Univ. (3), Osaka Univ. (2), GSI (1), NAO (1)) was the first attempt to
measure the cross sections of 8 Li(d, t) 7 Li reaction, which has been thought to play an
important role in destroying 8 Li nuclei and therefore limiting the synthesis of elements
over the mass of 8. By using the 8 Li beam from the TRIAC, the measurements were
made at seven different energies of 0.18, 0.24, 0.30, 0.40, 0.46, 0.60, and 0.75
MeV/nucleon, respectively corresponding to center-of-mass energies (Ecm) of 0.3, 0.4,
0.5, 0.7, 0.8, 1.0, and 1.1 MeV. Those Ecm cover the Gamow peaks of T9 = 1-3.
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