Speaker
Description
Research on short-lived unstable nuclei (radioactive isotopes, RI) has progressed rapidly in recent years, driven by advances in accelerator technology as well as RI production and separation techniques. Consequently, nuclear reaction experiments with rare RIs far from the valley of stability have been drawing increasing attention. To improve the measurement accuracy of nuclear reactions with rare RI beams, we propose a beam recycling technique utilizing a heavy-ion storage ring.
RI beams are generally secondary beams with lower quality (i.e., greater momentum dispersion and emittance) and lower intensity compared to beams of stable nuclei, often necessitating the use of thicker targets in nuclear reaction experiments. At the target, nearly all RI beams do not undergo nuclear reactions and are subsequently dumped, making it difficult to obtain sufficient event yields. These factors reduce the measurement accuracy. In the beam recycling technique, RI beams are accumulated in a heavy-ion storage ring equipped with an internal thin target until a nuclear reaction occurs. The energy loss, energy straggling, and transverse angular straggling of the accumulated RI beams as they pass through the internal target are corrected turn by turn and particle by particle. These corrections maintain high beam quality throughout the accumulation process.
To develop the beam recycling technique, the Recycled-Unstable-Nuclear Beam Accumulator (RUNBA) is currently under construction at RIKEN RIBF. RUNBA is a heavy-ion storage ring with a circumference of 26.6 m and is equipped with a beam recycling system consisting of an internal target, an accelerator cavity, an energy dispersion corrector, and transverse angular dispersion correctors. A singly charged RI beam produced by an ISOL system is converted into a fully stripped RI beam at 10 keV/nucleon by a charge breeder and then injected into RUNBA. The accumulated RI beams in RUNBA are re-accelerated up to 10 MeV/nucleon. With an accumulation time of 1 second in RUNBA, a collisional luminosity of 10$^{24}$ cm$^{-2}$·s$^{-1}$ can be achieved, assuming an RI production rate of 1 Hz and a target thickness of 10$^{18}$ atoms/cm$^{2}$. We estimated the required performance of the beam recycling system to achieve the accumulation time of 1 second based on particle motion analysis in RUNBA. This presentation details the conceptual design of RUNBA and the results of particle motion analysis.
| Email address | ryo.ogawara@riken.jp |
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| Funding Agency | This work was supported by JST FOREST Program, Grant Number JPMJFR222Z. |
| Classification | Storage rings |
