Characteristics of neutron resonance densitometry, 2; Neutron resonance capture analysis

Tsuchiya, Harufumi; Harada, Hideo; Koizumi, Mitsuo; Kitatani, Fumito; Kureta, Masatoshi; Becker, B.*; Kopecky, S.*; Heyse, J.*; Paradela, C.*; Mondelaers, W.*; et al.

Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-36-Kai Nenji Taikai Rombunshu (Internet), 9 Pages, 2015/12

Neutron Resonance Densitometry (NRD) was developed as a non-destructive assay to quantify U and Pu isotopes in particle-like debris. NRD is composed of neutron resonance transmission analysis (NRTA) and Neutron Resonance Capture Analysis (NRCA) or Prompt Gamma-ray Analysis (PGA). NRCA/PGA in NRD plays a role of identifying impurities in debris under the high-radiation field primarily caused by Cs. For this purpose, a novel LaBr -ray detector employing specific shields has been newly developed. With the developed -ray detector, a demonstration NRCA experiment was performed at a neutron time of flight facility GELINA (Belgium). As a result, samples (Hf, Gd, Ni) placed in a black box that is completely sealed by third party were successfully identified by the experiment. This presentation explains the design concept of the ray detector including its detection principle and details of the demonstration NRCA experiment.

NRD demonstration experiments at GELINA

Paradela, C.*; Alaerts, G.*; Becker, B.*; Harada, Hideo; Heyse, J.*; Kitatani, Fumito; Koizumi, Mitsuo; Kopecky, S.*; Mondelaers, W.*; Moens, A.*; et al.

EUR-27507-EN, 16 Pages, 2015/04

https://doi.org/10.2787/211881

Isomeric states observed in heavy neutron-rich nuclei populated in the fragmentation of a Pb beam

Steer, S. J.*; Podolyk, Z.*; Pietri, S.*; Grska, M.*; Grawe, H.*; Maier, K.*; Regan, P. H.*; Rudolph, D.*; Garnsworthy, A. B.*; Hoischen, R.*; et al.

Physical Review C, 84(4), p.044313_1 - 044313_22, 2011/10

https://doi.org/10.1103/PhysRevC.84.044313

Heavy neutron-rich nuclei were populated via the fragmentation of a E/A=1 GeV Pb beam. Secondary fragments were separated and identified and subsequently implanted in a passive stopper. By the detection of delayed rays, isomeric decays associated with these nuclei have been identified. A total of 49 isomers were detected, with the majority of them observed for the first time. Possible level schemes are constructed and the structure of the nuclei discussed. To aid the interpretation, shell-model as well as BCS calculations were performed.

Neutron-proton pairing competition in nuclei; Metastable state decays in the proton dripline nuclei Nb and Tc

Garnsworthy, A. B.*; Regan, P. H.*; Cceres, L.*; Pietri, S.*; Sun, Y.*; Rudolph, D.*; Grska, M.*; Podolyk, Z.*; Steer, S. J.*; Hoischen, R.*; et al.

Physics Letters B, 660(4), p.326 - 330, 2008/02

https://doi.org/10.1016/j.physletb.2008.01.017

The low-lying structures of the self-conjugate () nuclei Nb and Tc have been investigated using isomeric-decay spectroscopy following the projectile fragmentation of a Ag beam. These represent the heaviest odd-odd nuclei in which internal decays have been identified to date. The resulting level schemes shed light on the shape evolution along the line between the doubly-magic systems Ni and Sn and support a preference for states in odd-odd nuclei at low excitation energies associated with a neutron-proton pairing gap. Comparison with Projected Shell Model calculations suggests that the decay in Nb may be interpreted as an isospin-changing isomer.

Recent results in fragmentation isomer spectroscopy with rising

Pietri, S.*; Regan, P. H.*; Podolyk, Zs.*; Rudolph, D.*; Steer, S. J.*; Garnsworthy, A. B.*; Werner-Malento, E.*; Hoischen, R.*; Grska, M.*; Gerl, J.*; et al.

Nuclear Instruments and Methods in Physics Research B, 261(1-2), p.1079 - 1083, 2007/08

https://doi.org/10.1016/j.nimb.2007.04.219

The first results from the stopped beam RISING experimental campaign performed at the GSI laboratory in Darmstadt, Germany, are presented. RISING constitutes a major new experimental program in European nuclear structure physics research aimed at using relativistic energy (typically around 1 GeV per nucleon) projectile fragmentation reactions to populate nuclei with highly exotic proton-to-neutron ratios compared to the line of beta stability. In its high-efficiency stopped beam configuration, the RISING -ray spectrometer consists of 105 individual germanium crystals which view a focal plane in which the exotic nuclei are brought to rest. Here, decays from metastable states with half-lives in the nano to milliseconds range can be observed. Results of initial commissioning experiments are also shown and details of the planned future experimental program are given.

The mirrors Ca and S; A Test for isospin symmetry of shell gaps at the driplines

Doornenbal, P.*; Reiter, P.*; Grawe, H.*; Otsuka, Takaharu*; Al-Khatib, A.*; Banu, A.*; Beck, T.*; Becker, F.*; Bednarczyk, P.*; Benzoni, G.*; et al.

Physics Letters B, 647(4), p.237 - 242, 2007/04

https://doi.org/10.1016/j.physletb.2007.02.001

The first excited state of Ca was measured at GSI for the first time. The measured energy is found to be 3015(16) keV, which is lower than its mirror nucleus S by as large as 276 keV. The structure of those nuclei is studied by the shell model. It is found that those nuclei can be well described by the valence space. The large energy shift between them is caused by the Thomas-Ehrman effect. We presented that the energy shift in the shell region can be explained by the shell model with a phenomenological treatment of the Thomas-Ehrman effect.

Effects of and heavy ion damage on the time-resolved gain of a low breakdown voltage Si avalanche photodiode

Laird, J. S.*; Onoda, Shinobu; Hirao, Toshio; Becker, H.*; Johnston, A.*; Ito, Hisayoshi

Proceedings of 7th International Workshop on Radiation Effects on Semiconductor Devices for Space Application (RASEDA-7), p.37 - 40, 2006/10

no abstracts in English

Characterization of nuclear material by neutron resonance transmission analysis

Schillebeeckx, P.*; Alaerts, G.*; Becker, B.*; Paradela, C.*; Heyse, J.*; Kopecky, S.*; Vendelbo, D.*; Wynants, R.*; Harada, Hideo; Kitatani, Fumito; et al.

no journal, , 

The appearance of resonance structures in neutron induced reaction cross sections are fingerprints to study properties of materials and objects. Resonance structures are the basis of an analytical technique, i.e. Neutron Resonance Transmission Analysis (NRTA), which is being developed at the time-of-flight facility GELINA of the JRC-IRMM to characterize special nuclear materials. NRTA is based on the analysis of dips in a transmission spectrum that is obtained from a measurement of the attenuation of the neutron beam by a sample. To apply NRTA for the analysis of particle like debris samples of melted fuel produced in a severe nuclear accident is not evident. From this work one concludes that the accuracy of the results is strongly affected by the characteristics of the samples, in particular by the presence of neutron absorbing impurities, e.g. B, and the variety in shape and size of the particle like debris samples. To account for these effects, improved data analysis procedures and interpretation models have been developed. These procedures and models will be presented and validated by results of measurements carried out at GELINA. It will be demonstrated that the relative amount of fissile material can be derived absolutely with an accuracy better than 2% without the need of calibration samples, even in the presence of strong neutron absorbing materials.

A Conceptual NRD system and its performance evaluation

Tsuchiya, Harufumi; Harada, Hideo; Koizumi, Mitsuo; Kitatani, Fumito; Kureta, Masatoshi; Takamine, Jun; Iimura, Hideki; Kimura, Atsushi; Becker, B.*; Heyse, J.*; et al.

no journal, , 

Neutron Resonance Densitometry (NRD) is a non-destructive method using a pulsed neutron beam in order to quantify nuclear materials in particle-like debris of melted fuel that is generated by a severe accident like the one at the Fukushima Daiichi Nuclear Power Plant. It is a combination of neutron resonance transmission analysis (NRTA) and neutron resonance captures analysis (NRCA) or Prompt Gamma-ray Analysis (PGA). NRCA/PGA in NRD, using a newly designed -ray detector, plays a role of measuring impurities in debris that would have high radioactivity derived from Cs. Especially, the -ray detector was specially designed to measure 478-keV rays radiated by B under the presence of Cs. Then utilizing information on the amount of impurities obtained by NRCA/PGA, NRTA quantifies special nuclear materials in debris. To verify the effectiveness of NRD for quantifying nuclear materials, NRTA and NRCA/PGA experiments were conducted at GELINA, IRMM, by an international collaboration of JAEA and EC/JRC/IRMM. In addition, achievable accuracy concerning NRD was studied by Monte Carlo simulations. In this contribution, these achievements on NRD as well as its concept are reviewed.