Program - Brookhaven National Laboratory

is an indirect way of determining cross sections for nuclear reactions that proceed through a compound
nucleus. This technique may enable neutron-induced cross sections to be extracted for short-lived nuclei
that otherwise cannot be measured. However, because of the dependence of the populated spin-parity
distribution on the entrance channel, the validity of the surrogate method has to be investigated. The
CENBG collaboration has successfully applied this technique to determine the (n,f) cross sections of several
short-lived nuclei [1]. Since few years we investigate the validity of the surrogate technique to determine
capture cross sections. For this purpose we studied recently the surrogate reactions 174 Yb( 3 He, 4 He) 173 Yb
and 174 Yb( 3 He,p) 176 Lu to infer the well known 172 Yb(n, γ) and 175 Lu(n, γ) cross sections, respectively. The
surrogate gamma-decay probabilities found are several times higher than the neutron-induced ones. This
is due to the high spin-parity selectivity of neutron emission [2]. This selectivity is expected to strongly
decrease with increasing mass of the decaying nucleus and with increasing excitation energy. To verify
this conjecture we have made an experiment at the Oslo Cyclotron in June 2012 to study the reactions
238 U(d,pγ) 239 U, 238 U( 3 He,tγ) 238 Np, 238 U( 3 He, 4 Heγ) 237 U as surrogates for the 238 U(n, γ), 237 Np(n, γ) and
236 U(n, γ) cross sections, respectively. The experimental procedure and the first results will be presented.
[1] G. Kessedjian et al., Phys. Lett. B 692 (2010) 297 [2] G. Boutoux et al., Phys. Lett. B 712 (2012) 319
JF 3 11:20 AM
Surrogate Research at JAEA/Tokyo Tech
S. Chiba
Tokyo Institute of Technology
K. Nishio, H. Makii, I. Nishinaka, O. Iwamoto, T. Ishii, O. Ohta, M. Asai, K. Furutaka
Japan Atomic Energy Agency
Y. Aritomo
Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research
T. Nagayama
Ibaraki University
We will present a status of researchs in surrogate reaction method using heavy-ions to determine neutron
fission and capture cross sections of unstable nuclei. We take advantage of having 1) an electrostatic
tandem accelerator which can deliver highly mono-energetic beams of heavy ions, 2) rich experience in inbeam
γ spectroscopy, 3) rich experience in measuring fission fragments induced by heavy-ions, 4) nuclear
theory and evaluation experiences. We have construced appratus to measure fission fragments and γ-rays
in coincidence with ejectiles by which we can identify the populated compound nuclei. Primarily, we
used 18 O-induced reactions as well as 3 He-induced reactions. We also investigated conditions under which
which such measurements lead to correct neutron cross sections. Results of the theoretical researches were
published in a series of papers[1-4]. In this presentation, status of results of the above researches will be
summarized.
[1] S. Chiba and O. Iwamoto, Phys. Rev. C 81, 044604-1-6(2010). [2] K. Ogata, S. Hashimoto and S.
Chiba, J. Nucl. Sci. Technol. 48, 1337-1342(2011). [3] Y. Aritomo, S. Chiba and K. Nishio, Phys. Rev.
C 84, 024602-1-10(2011). [4] S. Chiba, O. Iwamoto and Y. Aritomo, Phys Rev. C 84, 054602-1-5(2011).
JF 4 11:40 AM
Validating (d,pγ ) as a Surrogate for Neutron Capture on Unstable Nuclei
J.A. Cizewski, A.S. Adekola, A. Ratkiewicz, M.E. Howard, B. Manning, C. Shand, Rutgers University,
New Brunswick, NJ USA. A.J. Couture, M. Devlin, N. Fotiades, R.O. Nelson, J.M. O’Donnell, Los
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