Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 51 (2018)

β-NQR measurement of the 23 Ne ground state
H. Nishibata,∗1 A. Gladkov,∗1,∗2 T. Kawaguchi,∗3 H. Ueno, ∗1 Y. Ichikawa,∗1 A. Takamine,∗1 T. Sato,∗1
K. Kawata,∗1,∗4 H. Yamazaki,∗1 W. Kobayashi,∗3 M. Sanjo,∗3 L. C. Tao,∗5 Y. Namamura,∗3 T. Asakawa,∗3Y. Sasaki,∗3 K. Totsuka,∗3 K. Doi,∗3 T. Yada,∗3 K. Asahi,∗1 Y. Ishibashi,∗6 K. Imamura,∗7 T. Fujita,∗8G. Georgiev,∗9 and J. M. Daugas∗10were located above and below the crystal. Each telescope consists of a stack of three 1.0-mm thick plastic
scintillators. The telescopes cover approximately 50%of the entire solid angle.
In the experiment, we first measured the g-factor of
the 23 Ne ground state with a NaF polycrystalline stopper by the β-NMR method to confirm the polarizationof the 23 Ne beam. In this measurement, we observed anuclear magnetic resonance at 1653.8(5) kHz; thus, ag-factor of g = 0.43305(14) was deduced. The obtainedg-factor is consistent with the literature values g =0.432(4)3) and 0.43268(36).4) The polarization of the23Ne beam was also determined to be AP = 5.0(4)%.
After measuring the g-factor, we performed the βNQR measurement of 23 Ne by using the ZnO singlecrystal. Figure 1 shows the obtained β-NQR spectrumof 23 Ne in the ZnO single crystal. In the figure, a clear
β-ray asymmetry change is found at νQ (= eqQ/h) =1.08(5)×103 kHz. From the obtained νQ and the Qmoment [Q = 145(13) emb],2) the electric field gradient q was determined to be |q| = 31(3)×1019 [V/m2 ].
Now, we are ready to measure the ground-state electromagnetic moments of neutron-rich Ne isotopes.
2.5

β-ray asymmetry change AP (%)

In this report, we present some results of the experimental program NP1612-RRC47. The aim of thisexperiment is to search for an appropriate single crystal for the β-NMR measurement of Ne isotopes andto measure its electric field gradient at the sitting siteof Ne, as the first step to the nuclear electromagneticmoment measurement of neutron-rich Ne isotopes. In
the present study, we applied the β-NQR method1) tothe spin-polarized 23 Ne, the ground-state Q momentof which has been well-studied,2) implanted into theZnO single crystal.
The experiment was conducted using the RIKEN
projectile fragment separator (RIPS). A radioactive
23Ne beam was obtained from the single-neutron
pickup reaction of 22 Ne at 70 MeV/nucleon on a 0.25mm thick Be target. In order to produce spin polarization, the primary beam was injected with a tilt angleof 2◦ with respect to the spectrometer entrance (F0),where the Be target was located. Fragments were accepted at a finite angle θ = 1◦ –3◦ to the primary beam
direction, and the center of the momentum distribution (∆p/p ≤ | ± 0.25%|) was selected at momentum
dispersive focal plane F1. A secondary beam of 23 Ne
with a purity higher than 90% was separated with a321-mg/cm2 thick Al wedge degrader. The intensityof the spin-polarized 23 Ne was 5×104 pps with a 22 Ne
beam intensity of 400 pnA.
The spin-polarized 23 Ne was implanted in a ZnO
single crystal (28 mm × 20 mm × 0.5 mm, inclinedat 45◦ to the horizontal plane), which was located at
the center of the β-NMR apparatus. The c-axis ofthe ZnO single crystal was along the vertical axis. A
static magnetic field of 0.5 T was applied to the crystal
parallel to its c-axis, and an oscillating magnetic field
was applied by a pair of RF coils perpendicular to thestatic magnetic field. The crystal was cooled to T ∼50 K to achieve a longer spin-lattice relaxation timethan the 23 Ne β-decay half-life (T1/2 = 37 s).
The β rays from the β decay of 23 Ne was detected
through a vacuum chamber wall, made of 1-mm thickfiber-reinforced plastic, by two β-ray telescopes which

2.023Ne in ZnO
T = 47 K

1.5
1.00.50−0.5700

800900 1000 1100 1200 1300 1400

νQ (=eqQ/h) [kHz]Fig. 1. Beta-NQR spectrum of 23 Ne implanted into theZnO single crystal. The dashed line shows the leastchi-square fitting result with a Gaussian function plus
a constant. The horizontal error bars indicate the widthof the swept frequency (∆νQ = 1.5 × 102 kHz).

∗1RIKEN Nishina Center
Department of Physics, Kyungpook National University∗3 Department of Physics, Hosei University∗4 Center for Nuclear Study, University of Tokyo∗5 School of Physics, Peking University∗6 Cyclotron and Radioisotope Center, Tohoku University∗7 Department of Physics, Okayama University∗8 Department of Physics, Osaka University∗9 CSNSM, CNRS/IN2P3, Université Paris-Sud∗10 CEA, DAM, DIF

References∗21) D. Nagae et al., Nucl. Instrum. Methods B 266, 4612
(2008).
2) W. Geithner et al., Phys. Rev. C 71, 064319 (2005).
3) D. A. Dobson, S. R. Brown, Bull. Am. Phys. Soc. 13(2), 173, CD3 (1968).
4) R. Matsumiya et al., OULNS Ann. Rept. 2004, 51(2005).

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