Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 51 (2018)

New isotope of 39 Na and the neutron dripline of neon isotopes using
a 345 MeV/nucleon 48 Ca beam
D. S. Ahn,∗1 N. Fukuda,∗1 H. Suzuki,∗1 Y. Shimizu,∗1 H. Takeda,∗1 T. Sumikama,∗1 H. Ueno,∗1 K. Yoshida,∗1N. Inabe,∗1 H. Sato,∗1 H. Baba,∗1 T. Komatsubara,∗1 Y. Yanagisawa,∗1 K. Kusaka,∗1 M. Ohtake,∗1 H. Otsu,∗1T. Kubo∗1,∗2 O. B. Tarasov,∗1,∗2 B. M. Sherrill,∗1,∗2 D. J. Morrissey,∗1,∗2 D. Bazin,∗1,∗2 T. Nakamura,∗1,∗3J. Amano,∗1,∗4 N. Iwasa,∗1,∗5 S. Ishikawa,∗1,∗5 T. Sakakibara,∗1,∗5 and H. Geissel∗1,∗6Table 1. Experimental conditions.

The neutron dripline drawn between bound and unbound nuclei is important to verify the mass models
and to understand nuclear structures. In 2014 experiment,1) a search for 33 F and 36 Ne isotopes was performed to determine the neutron dripline. The nonobservation for these isotopes indicates that they areunbound.
In April 2017, the experiment (proposal number:DA16-01-01) was carried out, aiming to search the existence of a new 39 Na (Z = 11, N = 28) isotope as shownin Fig. 1 and to determine the neutron dripline for neon
isotopes. High statistics data of 36 Ne isotope were also
obtained to conﬁrm the previous non-observation.

Settings
TargetF1 degrader
F5 degraderBρ
Momentum acceptanceAtomic number ZFig. 1. New isotope of Na with the neutron number
N =28 and neutron dripline.

∗3∗4∗5∗636Ne
Be 20 mm
Al 15 mm
Al 7 mm
9.4077 mm
± 3%

15102

Preliminary result

141340Mg

121039Na

11The neutron-rich neon and sodium isotopes were
produced by the projectile-fragmentation of a 48 Ca
beam with an energy of 345 MeV/nucleon at RIKEN
RIBF. The high-intensity beam made it possible tosearch the neutron dripline. The magnetic rigidity(Bρ) of the ﬁrst dipole magent using the BigRIPS2)
separator was tuned for the 39 Na isotope. Two wedgeshaped degraders at the F1 and F5 dispersive foci wereused to purify the RI beams. A thick collimator3) madeof an SUS material with 50-cm thickness was installedat the F2 focal plane to reject tritons and other lightparticles. The diﬀerent Bρ value was tuned for the36Ne isotope. The experimental conditions for 39 Na
and 36 Ne settings are summarized in Table 1.
The particle identiﬁcation (PID) was conducted using the TOF-Bρ-∆E method.4) Figure 2 shows a pre∗2NaBe 20 mm
Al 15 mm
Al 7 mm
9.155 Tm
± 3%liminary PID plot for the 39 Na setting. The newisotope of 39 Na was clearly observed. The nonobservation of any events corresponding to 38 Na indicates that it is unbound. In this experiment, wealso determined the dripline of neon isotopes with ahigh conﬁdence level. The detailed data analysis iscurrently in progress.

39∗139

1093

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

1

mass-to-charge ratio A/QFig. 2. Preliminary PID plot for the 39 Na setting.

References
1) N. Fukuda, T. Kubo et al., to be submitted.
2) T. Kubo et al., Nucl. Instrum. Methods Phys. Res. B
204, 97 (2003).
3) D. S. Ahn et al., RIKEN Accel. Prog. Rep. 50, 85 (2017).
4) N. Fukuda et al., Nucl. Instrum. Methods Phys. Res. B
317, 323 (2013).

RIKEN Nishina Center
FRIB/NSCL, Michigan State University
Department of Physics, Tokyo Institute of Technology
Department of Physics, Rikkyo University
Department of Physics, Tohoku University
GSI Helmholtzzentrum für Schwerionenforschung- 82 -