II-9. Instrumentation

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Conceptual design of a heavy ion storage ring RUNBA
M. Wakasugi,∗1,∗2 T. Ohnishi,∗1 R. Ogawara,∗1,∗2 S. Takagi,∗2 K. Kuze,∗2 and Y. Yamaguchi∗1
We plan to construct a heavy ion storage ring,
RUNBA (Recycled-Unstable-Nuclear Beam Accumulator) adjacent to the SCRIT facility in the E21 experimental room. RUNBA will be a research and development machine for developing and establishing a beam
recycling technique in a storage ring for application tonuclear reaction studies for rare RI beam. This project isongoing under the joint research program between ICR
Kyoto University and RIKEN Nishina Center (RNC). In
the last year, we transfered the storage ring (sLSR),1)
which was avandoned for more than ten years, from ICR
to RNC. RUNBA is a rebuilt machine of sLSR and weare designing the lattice structure and machine layout inE21. Figure 1 shows a current ﬂoor plan of the RUNBA
facility. RUNBA will be connected to ERIS, which is an
ISOL system for SCRIT experiments.
Continuous singly-charged ion beams from ERIS are
converted into a pulsed ion beam by FRAC and a highlycharged ion beam by RECB (Resonant Extraction
Charge Breeder),2) which is under development at ICR.
A fully-stripped pulsed ion beam with 10 keV/nucleon
is injected into RUNBA with a multi-turn injection
method. Consequently, it can be accelerated up to
10 MeV/nucleon by repeating ﬁve times the acceleration
process in which the ion velocity doubled by sweeping
an RF frequency at the non-resonant ferrite cavity andsynchronously ramping up the magnetic ﬁeld.
The concept of beam recycling is that the energy loss,energy straggling, and transverse angular straggling produced when the beam passes through the internal target are corrected turn by turn and particle by particle, and beam circulation is stably maintained until nuclear reaction occurs at the target. Therefore, devices
required to be equipped in RUNBA in addition to theFig. 1. A plane view of RUNBA facility.
∗1∗2

RIKEN Nishina Center
ICR, Kyoto University

Fig. 2. Beta and dispersion functions of RUNBA.
Table 1. Lattice structure and properties of RUNBA.
Circumference (m)Maximum Bρ (Tm)Transition γ
Harmonics (10 keV/nucleon, 10 MeV/nucleon)
RF frequency (MHz)
Tunes (νx , νy )Max. dispersion functions (ηx , ηy ) (m)at focal point
Beta functions (βx , βy ) (m)Dispersion functions (ηx , ηy ) (m)26.5571.05
1.855(32, 1)1.674–3.348(2.368, 1.695)(3.497, 0.0)
(0.697, 0.527)(0.0, 0.0)

fundamental optical elements include an internal target
system, acceleration cavity, energy-dispersion corrector,and transverse emittance corrector. The fundamental
properties in the current design of RUNBA are summarized in Table 1. The beta and dispersion functions over
the whole ring are shown in Fig. 2. RUNBA optics isformed with 6 bending magnets, 3-family 12 quadrupolemagnets, 2-family 4 sextupole magnets, and a triplebend achromatic arc structure that is adopted to provide achromatic focus points for internal target insertionin the straight section. In another straight section, an
energy-dispersion corrector will be installed and emittance correctors in the horizontal and vertical directions
are placed at positions where the betatron phase advances are 0.75 from the target. The diﬀusion of energy
spread would be suppressed by giving appropriate positive or negative energy gain determined from the diﬀerence in ﬂight time from the target to energy-dispersion
corrector. The emittance correctors transversely kickions according to the transverse position measured at
the target. These new feedback systems are now being
developed at ICR.
References

1) A. Noda et al., Proc. EPAC2006, 237 (2006).
2) R. Ogawara et al., in this report.

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