Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 50 (2017)

Production cross section measurements of Ne isotopes with a 48Ca beam
D. S. Ahn,㻖1 N. Fukuda,㻖1 H. Suzuki,㻖1 Y. Shimizu,㻖1 H. Takeda,㻖1 T. Sumikama,㻖1 D. Murai,㻖1,㻖2 J. Amano,㻖1,㻖2N. Inabe,㻖1 K. Yoshida,㻖1 Y. Yanagisawa,㻖1 K. Kusaka,㻖1 M . Ohtake,㻖1 T. Komatsubara,㻖1 H. Sato,㻖1 H. Ueno,㻖1 andT. Kubo㻖1,㻖3
Particle identification was performed using theTOF-BU-'E method.3) Fig. 2 shows the production crosssections of neutron-rich Ne isotopes. The experimental
results obtained in the 2008-20101) and 2014 experiments
are also shown in Fig. 2. Different collimators were used in
the previous experiments as follows: SUS material with
30-cm thickness for the 2008-20101) experiment and45-cm-thick iron blocks with a large aperture for the 2014
experiment. The black line represents an empirical formulaof the EPAX 2.154) parameterizations in the LISE++
calculation.5) The present results are in good agreement withboth the previous experimental results and the predictions.
However, the measured production cross sections of the31,34
Ne isotopes are slightly underestimated.

The systematic trends of production cross sections arenecessary to predict the production rates of rare isotopes,
and important to search for new isotopes and the neutron
drip line. Comparison of expected and measured yields isimportant to ascertain whether bound states exist in isotopes
such as 39Na. Expected yields for 39Na (Z = 11) can be
estimated from the neighboring isotopes. We measured theproduction cross sections of very neutron-rich Ne (Z = 10)
isotopes. In the previous experiment,1) the cross sections formany Ne isotopes were obtained with low transmission(2~5% in the worst cases). In this experiment, theproduction cross sections of neutron-rich 29-34Ne isotopes
were measured with optimized settings for each isotope. As
each isotope passed through a central orbit, a hightransmission was achieved.
Ne isotopes were produced by the projectile
fragmentation of a 48Ca beam at an energy of 345
MeV/nucleon using the BigRIPS separator2) of RIKEN
RIBF. The same target (Be: 20 mm) and the same thickness
degraders were used for both F1 (Al: 15 mm) and F5 (Al: 8mm). The F5 degrader was used to reject contaminants inthe form of light particles. A thick collimator installed
before the F2 slits was developed as shown in Fig. 1. Thecollimator was made of an SUS material with a 50-cm
thickness to block most contaminants, including tritons andother light particles. The aperture of the collimator wasdesigned with horizontal and vertical angular acceptancesof s 20 mrad and s 30 mrad, respectively, whichcorrespond to s7.5 mm in the horizontal direction at theF2 focal plane. Additional iron blocks were also installed tocover both sides of the collimator.

Fig. 2. Preliminary results of production cross sections ofvery neutron-rich Ne isotopes up to the heaviest known
isotope, 34Ne. The filled red circles represent theexperimental results obtained from the 2016 experiment.
The green, orange, violet, and pink rectangles represent theexperimental results obtained from the 2008,1) 2009,1)
2010,1) and 2014 experiments, respectively. The
experimental measurements are compared with the EPAX
2.15 parameterizations indicated by the black line.
References
1) H. Suzuki et al., Nucl. Instrum. Meth. Phys. Res. B317, 756(2013).
2) T. Kubo et al., Nucl. Instrum. Meth. Phys. Res. B204, 97(2003).
3) N. Fukuda et al., Nucl. Instrum. Meth. Phys. Res. B317, 323(2013).
4) K. Sümmer, B. Blank, Phys. Rev. C 61, 034607 (2000).
5) O. B. Tarasov, D. Bazin, Nucl. Instrum. Meth. Phys. Res. B266,4657 (2008).

Fig 1. Schematic view of collimator and iron blocks at F2.
䠆1

RIKEN Nishina Center
Department of Physics, Rikkyo University
䠆3FRIB/NSCL, Michigan State University
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