4th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 59, Number 10
Tuesday–Saturday, October 7–11, 2014;
Waikoloa, Hawaii
Session 1WH: Applications of Nuclear Reactions with Gamma-rays and Surrogates for Neutrons
9:00 AM–12:30 PM,
Tuesday, October 7, 2014
Room: Kona 2
Chair: Calvin Howell, Duke University
Abstract ID: BAPS.2014.HAW.1WH.1
Abstract: 1WH.00001 : The Science of Nuclear Materials Detection using gamma-ray beams: Nuclear Resonance Fluorescence*
9:00 AM–9:30 AM
Preview Abstract
Abstract
Author:
Hideaki Ohgaki
(Kyoto University)
An atomic nucleus is excited by absorption of incident photons with an
energy the same as the excitation energy of the level, and subsequently a
gamma-ray is emitted as it de-excites. This phenomenon is called Nuclear
Resonance Fluorescence and mostly used for studies on Nuclear Physics field.
By measuring the NRF gamma-rays, we can identify nuclear species in any
materials because the energies of the NRF gamma-rays uniquely depend on the
nuclear species. For example, $^{\mathrm{235}}$U has an excitation level at
1733~keV. If we irradiate a material including $^{235}$U with a
gamma-ray tuned at this excitation level, the material absorbs the gamma-ray
and re-emits another gamma-ray immediately to move back towards the ground
state. Therefore we can detect the $^{\mathrm{235}}$U by measuring the
re-emitted (NRF) gamma-rays. Several inspection methods using gamma-rays,
which can penetrate a thick shielding have been proposed and examined.
Bertozzi and Ledoux have proposed an application of nuclear resonance
fluorescence (NRF) by using bremsstrahlung radiations. However the
signal-to-noise (SN) ratio of the NRF measurement with the bremsstrahlung
radiation is, in general, low. Only a part of the incident photons makes NRF
with a narrow resonant band (meV-eV) whereas most of incident radiation is
scattered by atomic processes in which the reaction rate is higher than that
of NRF by several orders of magnitudes and causes a background. Thus, the
NRF with a gamma-ray quasi-monochromatic radiation beam is proposed. The
monochromatic gamma-rays are generated by using laser Compton scattering
(LCS) of electrons and intense laser photons by putting a collimator to
restrict the gamma-ray divergence downstream. The LCS gamma-ray, which is
energy-tunable and monochromatic, is an optimum apparatus for NRF
measurements
We have been conducted NRF experiment for nuclear research, especially with
high linear polarized gamma-ray generated by LCS, to survey the distribution
of M1 strength in MeV region in LCS facility in AIST, Japan. As well, 1-D,
2-D isotope imaging by using LCS gamma-ray and NRF has been conducted. Since
2009 we have started a development of a non-destructive inspection system
under the MEXT program in Japan. Series of experiments of the developing
system have been conducted in HIGS facility in Duke University and JAEA
Kansai Photon Science Institute. We will report on the recent result of
these experiments in the workshop.
*This work is supported by the special coordination funds for promoting science and technology in Japan (Grant No. 066).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.HAW.1WH.1