Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 48 (2015)

First production of 10 Be beam at CRIB and 10Be+α resonant elastic
scattering
H. Yamaguchi,∗1 D. Kahl,∗1 S. Hayakawa,∗1 Y. Sakaguchi,∗1 and T. Nakao,∗2 for CRIB collaboration∗1∗2

silicon detectors, which had thicknesses of 20 µm and480 µm, were placed in the gas-filled chamber, consisting of a “∆E-E” telescope. The telescope was locatedat 482 mm from the Mylar entrance window, exactly inthe direction of the beam axis. The energy of the beam
degraded and the beam was stopped by the thick gas
target and α particles originating from elastic scatterings reached the telescope. The energy spectrum of theα particles exhibited several peaks, as shown in Fig. 1.
In principle, α-cluster like resonances including theoretically predicted ones should be observed as peaksin the present measurement. In particular, two distinct peaks that likely correspond to resonances in 14 C
are observed at excitation energies of 14.3 MeV and16 MeV; however, the resonant features of those are
yet to be investigated. The peak at the highest energy
of approximately 17 MeV could be due to background
events arising from impurities in the 10 Be beam andshould be eliminated in the main run.
In summary, we successfully produced a 10 Be beamat CRIB for the first time and also showed that the resonant scattering measurement is feasible. The actual
measurement for 7.5 days will be performed in 2015.
140120Count (for 9 hours)

α-cluster states are known to occur in many nuclei,
including isotopes of the carbon nucleus. Among theα-cluster states, linear-chain cluster states have been
considered as exotic and of interest for a long time.
Although there have been many theoretical investigations, no clear experimental evidence has been obtained for such states thus far.
By performing an antisymmetrized molecular dynamics (AMD) calculation, Suhara and En’yo1,2) ob++tained a band (0+5 , 26 , 46 ) that could be explained
as linear-chain cluster levels of 14 C. It was predictedthat these levels appear a few MeV or more above the10B+α threshold, unlike the prolate bands in the studyof Oertzen et al.3) The investigation2) shows that theAMD wave function has a configuration in which two
α particles and two neutrons are located close to eachother, while the remaining α particle is relatively faraway. This implies that states having such a linearchain configuration could be accessed from the 10 Be+αchannel.
The aims of the present work are 1) to search fora linear-chain configuration via 10 Be+α resonant scattering, and 2) to determine the resonant parametersof the high excited states (13-18 MeV) of 14 C, which
are still mostly unknown, in order to elucidate on thecluster-band structure. The experimental method issimilar to that used in previous studies.4,5)
The study was conducted at the low-energy
radioactive-isotope (RI) beam separator CRIB. The10Be beam at CRIB was first produced on January
17-19, 2014. Using a 5.57 MeV/u primary 11 B beamfrom the AVF cyclotron and a 500-Torr cryogenic deuterium target, 10 Be particles were produced via the11B(d, 3 He)10 Be reaction in inverse kinematics. The+4 charge state was selected using the D1 dipole magnet of CRIB. The produced 10 Be4+ beam was contaminated with a small amount of 10 B4+ , which was mostly
excluded by inserting a 0.7 µm-thick Mylar film as acharge stripper at the F1 focal plane. The highest 10 Be
beam production rate was 2 ×104 pps at the final focal
plane (F3). The beam energy was 3.51 MeV/u before
reaching parallel-plate avalanche counters (PPACs) installed for the beam monitoring.
We also performed a test measurement of α resonant scattering using a chamber filled with helium gas
at 760 Torr, which served as the target for elastic scattering. The chamber had a window covered with a 25µm-thick Mylar film at the beam entrance. A pair ofCenter for Nuclear Study, University of Tokyo
Advanced Science Research Center, Japan Atomic Energy
AgencyEx~16 MeV

10080

Ex~14.3 MeV
60
4020002468101214161820

Measured alpha particle energy (MeV)

Fig. 1. Energy spectrum of α particles. The data wereaccumulated for 9 hours.

References
1) T. Suhara and Y. Kanada-En’yo: Phys. Rev. C 82,044301 (2010).
2) T. Suhara and Y. Kanada-En’yo: Phys. Rev. C 84,024328 (2011).
3) W. Oertzen, et al.: Eur. Phys. J. A21, 193 (2004).
4) H. Yamaguchi et al.: Phys. Rev. C 83, 034306 (2011).
5) H. Yamaguchi et al.: Phys. Rev. C 87, 034303 (2013).

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