Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 50 (2017)

Production of a 7Be implanted target
A. Inoue,䠆1 A. Tamii,䠆1,䠆7 H. Yamaguchi,䠆2 K. Abe,䠆2 S. Adachi䠆1 N. Aoi,䠆1,䠆7 M. Asai,䠆3 M. Fukuda,䠆4 G. Gay,䠆1T. Hashimoto,䠆5 S. Hayakawa,䠆2 E. Ideguchi,䠆1 N. Kobayashi,䠆1 Y. Maeda,䠆6 H. Makii,䠆3 K. Matsuta,䠆4,䠆7 M. Mihara,䠆4
M. Miura,䠆1 T. Shima,䠆1 H. Shimizu,䠆2 R. Tang,䠆1 T. D. Trong,䠆1 and L. Yang䠆2The beam system for reaction of isotope of long-life withlight-ions applying normal kinematics and implanted target(BRILLIANT) is a project to realize light-ion reaction withimplanted targets. The first application is for 7Be to measure
the 7Be(d, p) reaction for studying the primordial 7Li
production in Big-Bang nucleosynthesis (BBN).
The overestimation of primordial 7Li abundance in thestandard BBN model is one of the known and unresolved
problems in nuclear astrophysics. The latest theoretical
BBN model prediction of the primordial 7Li abundance isstill 3 times higher than the recent precise observation.1) A
key to solve the discrepancy is the destruction of 7Be, forwhich the 7Be(d, p)8Be and 7Be(n, Į)4He reactions are twopromising processes. It is suggested that the contribution
from 7Be(d, p)8Be is larger than that from 7Be(n, Į)4He.2,3) We
focus on the 7Be(d, p)8Be reaction. Present available data
are insufficient in terms of the accuracy or energy range.4,5)
We develop an unstable 7Be target for a high-resolution
measurement of the 7Be(d, p)8Be reaction in normal
kinematics, which is a great technical challenge. We call thetechnique “implantation method.” The 7Be particles are
implanted in a host material. Our goal is to implant 1×1012
7Be /mm2 in 29 h.6,7)
We performed an experiment in June 2016 to create the7
Be target at CRIB. The primary beam was 7Li2+, and thesecondary beam was produced by the 1H(7Li, 7Be) reaction.
The 7Be beam energy was 4.0 MeV/nucleon. We used a10-ȝm-thick Au foil as the host material after a 15-ȝm-thickAu foil as an energy degrader and a 2-mmǗ collimator(Fig. 1).

We checked the beam focus and position with the F2PPAC detector when the beam intensity was about 104 pps
at F2. The beam diameter at F2 was 10 mm. We implanted
7Be for 19 h after increasing the beam intensity to 1.1 eȝA.
The amount of implanted 7Be was measured by detecting
the 477-keV Ȗ-rays from the electron-capture decay of 7Be
using a LaBr3 detector. Thus, we could achieve theimplantation of 4×1010 7Be/mm2 in the first experiment.
The number is still smaller than the goal. We suspect thatthe beam-spot size and the beam position at F2 were notfully optimized for the high-intensity beam and not
maintained well during the long irradiation time.
As a next step, we plan to have a development beam time
to satisfy those conditions for producing a high-intensity
7
Be beam at CRIB.

Fig. 2. Comparison between the Ȗ-ray measurement of
the implanted target and the background. An obvious
477-keV peak appeared after the irradiation.

References
1) R. H. Cyburt et al., J. Cosmol. Astropart. Phys. 11, 012 (2008).
2) S. Q. Hou et al., Phys. Rev. C 91, 055802 (2015).
3) T. Kawabata et al., Phys. Rev. Lett. 118, 052701 (2017).
4) R. W. Kavanagh et al., Nucl. Phys. 18, 493 (1960).
5) C. Angulo et al., Astrophys. J. 630, L 105 (2005).
6) H. Yamaguchi et al., Nucl. Instr. Meth. A 589, 150 (2008).
7) G. Amadio et al., Nucl. Instr. Meth. A 590, 191 (2008).

Fig. 1. Set up in the CRIB F2 chamber.

䠆1

Research Center for Nuclear Physics, Osaka University
Center for Nuclear Study, University of Tokyo
䠆3
Japan Atomic Energy Agency
䠆4
Department of Physics, Osaka University
䠆5Rare Isotope Science Project, Institute for Basic Science䠆6
Department of Applied Physics, Faculty of Engineering, University ofMiyazaki
䠆7
RIKEN Nishina Center䠆2- 77 -