Ⅰ. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 49 (2016)

Beam commissioning of the rare-RI ring
Y. Yamaguchi,∗1 Y. Abe,∗1 D. Nagae,∗1 F. Suzaki,∗1,∗2 H. Miura,∗2 S. Ohmika,∗2 S. Naimi,∗1 Z. Ge,∗2T. Yamaguchi,∗2 A. Ozawa,∗3 S. Suzuki,∗3 Y. Yanagisawa,∗1 H. Suzuki,∗1 H. Baba,∗1 S. Michimasa,∗4 S. Ota,∗4T. Uesaka,∗1 M. Wakasugi,∗1 T. Watanabe,∗1 Y. Yano,∗1 and Rare-RI Ring Collaborators
We conducted two test experiments of the rare-RIring in 2015. The ﬁrst experiment using a 78 Kr primary beam with an energy of 168 MeV/u was performed in June. At that time, we succeeded in injecting a particle, which was randomly produced from aDC beam from cyclotrons, into the ring individuallywith a fast kicker system1) ; we extracted the particle
from the ring less than 1 ms after the injection2) . We
also checked the periodic signals of the circulated particle in the ring by using a carbon-foil with an MCP
detector3) . We measured the Time-Of-Flight (TOF)of the particles between the entrance and the exit ofthe ring to check the isochronism. By adjusting theﬁrst-order isochronous magnetic ﬁeld using trim-coils,
which were installed into the dipole magnets of thering, the isochronism of around 10-ppm was achieved
for the momentum spread of ±0.2%4) . In addition,
we conﬁrmed that a resonance-type Schottky pick-up
successfully acquired the revolution frequency information of one particle with a resolution of approximately
1.3 × 10−6 in a storage mode5) .
The second experiment was performed in December
by using a secondary beam to verify the principle ofmass determination using the following equation.
√m1
1 − β12m0 T1=(),(1)
qq T0 1 − ( TT1 β1 )20Fig. 1. (a) Timing signal of the detected particles at theplastic scintillation counter after injection by kicker
magnets. (b) Two-dimensional for particle identification before the F3 of BigRIPS. The red circle indicatesthe injected particles.

where m0,1 /q is the mass-to-charge ratio of the reference and interested particles, T0,1 is revolution time ofthese particles, β1 = v/c, v is the velocity of the interested particles, and c is the light velocity. The secondary beam was produced via the projectile fragmentation of a 345 MeV/u 48 Ca primary beam with a 9 Be
target. We identiﬁed the isotopes before the F3 achromatic focus of BigRIPS, and we injected particles tothe ring individually with the fast kicker system. Figure 1 (a) shows the timing signal of the detected particles using a plastic scintillation counter, which wasinstalled on the central orbit of the ring at the next
straight section of the kicker area. We conﬁrmed thatthese particles are 36 Ar and 35 Cl by using the ∆E-TOF
information eventually, as shown in Fig. 1 (b). Afterremoving the plastic scintillation counter from the central orbit of the ring, we checked the periodic signalsof these two types of particles by using the carbonfoil with the MCP detector3) . Finally we succeeded∗1∗2∗3∗4Fig. 2. Spectrum of TOF between the plastic scintillation
counter at S0 of SHARAQ and the plastic scintillation
counter at the exit area of R3 is shown. The peak onthe left side indicates extracted 36 Ar, whereas the peakon the right side indicates extracted 35 Cl.

in extracting these particles from the ring simultaneously. Figure 2 shows the result of the TOF between
the plastic scintillation counter at S0 of SHARAQ andthe plastic scintillation counter at the exit area of thering.
Oﬄine analysis is now in progress to determine therevolution time (T0,1 ) and the β1 values, which will allow the discussion of mass determination using equation (1).
References
1) Y. Yamaguchi et al.: Phys. Scr. T166 (2015) 014056.
2) H. Miura et al.: In this report.
3) D. Nagae et al.: In this report.
4) Y. Abe et al.: In this report.
5) F. Suzaki et al.: In this report.

RIKEN Nishina Center
Department of Physics, Saitama University
Institute of Physics, University of Tsukuba
Center for Nuclear Study, University of Tokyo- 18 -