Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 51 (2018)

Present status of data analysis of commissioning experimentusing exotic nuclei
D. Nagae,∗1 S. Omika,∗1,∗2 Y. Abe,∗1 Y. Yamaguchi,∗1 F. Suzaki,∗1 K. Wakayama,∗2 N. Tadano,∗2R. Igosawa,∗2 K. Inomata,∗2 H. Arakawa,∗2 K. Nishimuro,∗2 T. Fujii,∗2 T. Mitsui,∗2 T. Yamaguchi,∗2,∗3T. Suzuki,∗2 S. Suzuki,∗3 T. Moriguchi,∗3 M. Amano,∗3 D. Kamioka,∗3 A. Ozawa,∗3 S. Naimi,∗1 Z. Ge,∗1,∗2Y. Yanagisawa,∗1 H. Suzuki,∗1 H. Baba,∗1 S. Michimasa,∗4 S. Ota,∗4 G. Lorusso,∗5 Yu.A. Litvinov,∗6M. Wakasugi,∗1 T. Uesaka,∗1 and Y. Yano∗1

where m0,1 /q denote the mass-to-charge ratio of thereference particle and particle of interest, respectively;
T0,1 are the revolution times of these particles; andβ1 is the velocity of the particle of interest. Because
the isochronous condition is adjusted for the reference
particle, isochronism is not fulﬁlled for the particlesof interest. To evaluate masses of nuclei with nonisochronism, we correct their revolution time T1 by thevelocity measured upstream.
Exotic nuclei around 78 Ge were produced by in-ﬂight
ﬁssion of a 345 MeV/nucleon primary beam of 238 U on
a 10-mm thick 9 Be target. We identiﬁed these nuclei
before the F3 achromatic focus of BigRIPS. These nuclei were injected into the ring using the individual
injection method with the fast kicker system.3) The
isochronous magnetic ﬁeld in the ring was adjusted forthe reference particle 78 Ge with a precision of 5.4 ppm
for a momentum spread of ± 0.3%.4) The exotic nuclei
79As, 77 Ga, 76 Zn, and 75 Cu were successfully stored
for about 0.7 ms and extracted from the ring. Theseparticles, 79 As, 78 Ge, 77 Ga, 76 Zn, and 75 Cu, were circulated 1904 turns, 1880 turns, 1855 turns, 1828 turns,and 1801 turns, respectively. T0,1 for each nuclei werededuced from the TOF between the S0 achromatic focus of SHARAQ and the ring exit ELC, and the turnnumber. β1 was deduced from Bρ and the TOF between the F3 achromatic focus of BigRIPS and S0.
Figure 1 shows the deviations of experimental m/q
from their literature values listed in AME20165) asa function of m/q. The mass accuracies prelimi∗1∗2∗3∗4∗5∗6RIKEN Nishina Center
Department of Physics, Saitama University
Institute of Physics, University of Tsukuba
Center for Nuclear Study, University of Tokyo
Department of Physics, University of Surrey
GSI Helmholtzzentrum für Schwerionenforschung- 168 -

nary obtained for 79 As, 77 Ga, 76 Zn, and 75 Cu were
−2.2 × 10−5 , 1.9 × 10−5 , 2.5 × 10−5 , and 3.5 × 10−5 ,respectively. The statistical uncertainty that is taken
into account comes from measurements of T0 (∼ 10−6 )and T1 (∼ 10−6∼−5 ). Systematic uncertainty comingfrom β determination is of the order of about 10−5 .
A notable diﬀerence is observed between the experimental m/q and their literature values. The disagreement comes from the diﬀerence between the measured
β1 and in-ring β1 , which is due to the position-sensitive
detector PPAC that was used at F6 for momentum tagging. Further analysis for correction of this eﬀect is inprogress. For future experiments, a position-sensitive
detector with thin foil is needed to reduced the disagreement. Such a detector is now under development.6,7)
5.0 × 10-5m/qEXP - m/qlit

The Rare RI Ring1) is an isochronous storage ring
constructed to measure the masses of short-lived rare
nuclei using the time-of-ﬂight (TOF) measurement
method. In 2016, we performed a commissioning experiment using exotic nuclei with well-known masses2)
to conﬁrm the feasibility and principle of mass determination using the following equation:
�m0 T1 �
1 − β12m1
�=(1)�)2 ,(qq T0 �
T11−β1
T075

4.0 × 10-5
3.0 × 10-577

Ga76

Znryain

2.0 × 10-5
1.0 × 10
0.0-5

imler
P-1.0 × 10-5-2.0 × 10-5-3.0 × 10-5
2.35

Cu

79

As

2.40

2.45

2.50

2.55

2.60

2.65

m/qFig. 1. Diﬀerences between the m/q values obtained in thisanalysis and the corresponding values from the literature.5) The error bars that are shown contain only statistical contributions.

References
1) A. Ozawa et al., Prog. Theor. Exp. Phys. 2012, 03C009(2012).
2) D. Nagae et al., RIKEN Accel. Prog. Rep. 50, 18 (2017).
3) H. Miura et al., RIKEN Accel. Prog. Rep. 49, 154(2017).
4) Y. Yamaguchi et al., RIKEN Accel. Prog. Rep. 50, 183(2017).
5) M. Wang et al., Chin. Phys. C 41, 030003 (2017).
6) Z. Ge et al., In this report.
7) H. Li et al., In this report.