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Abstract. We present new spectral data of prompt -ray emission from the spontaneous fission of 252 Cf. This work was performed in direct response to an OECD/NEA high priority data request. We discuss the impact of our new data on evaluated nuclear data tables not only for this nuclide, but also for 238 U and 241 Pu, which are always produced in a reactor. Furthermore, we will show results from our investigation of prompt -ray emission from the reaction 235 U(n th , f), measured in at the Centre for Energy Research of the Hungarian Academy of Sciences in Budapest, Hungary. Spectral data obtained with three different detectors are consistent and led to an uncertainty on total energy and multiplicity considerably smaller than requested by the OECD/NEA.

Section: Prompt Fission -Ray Spectral Datamentioning

confidence: 90%

Section: -P4mentioning

confidence: 99%

Prompt fissionγ-rays from the reactions²⁵²Cf(SF) and²³⁵U(n_th, f) – new data

Oberstedt

Belgya

Billnert

et al. 2013

“…Many models that can predict neutron multiplicities for different systems are in development but for the moments they all require experimental fission-fragment mass and kinetic energy data as input parameter [4][5][6]. Unfortunately, for the moment, input data with sufficient accuracy are scarce and the excitation energy range is limited.…”

Section: Epj Web Of Conferencesmentioning

confidence: 99%

The VERDI fission fragment spectrometer

Frégeau

Bryś

Gamboni

et al. 2013

Abstract. The VERDI time-of-flight spectrometer is dedicated to measurements of fission product yields and of prompt neutron emission data. Pre-neutron fission-fragment masses will be determined by the double time-of-flight (TOF) technique. For this purpose an excellent time resolution is required. The time of flight of the fragments will be measured by electrostatic mirrors located near the target and the time signal coming from silicon detectors located at 50 cm on both sides of the target. This configuration, where the stop detector will provide us simultaneously with the kinetic energy of the fragment and timing information, significantly limits energy straggling in comparison to legacy experimental setup where a thin foil was usually used as a stop detector. In order to improve timing resolution, neutron transmutation doped silicon will be used. The high resistivity homogeneity of this material should significantly improve resolution in comparison to standard silicon detectors. Post-neutron fission fragment masses are obtained form the timeof-flight and the energy signal in the silicon detector. As an intermediary step a diamond detector will also be used as start detector located very close to the target. Previous tests have shown that poly-crystalline chemical vapour deposition (pCVD) diamonds provides a coincidence time resolution of 150 ps not allowing complete separation between very low-energy fission fragments, alpha particles and noise. New results from using artificial single-crystal diamonds (sCVD) show similar time resolution as from pCVD diamonds but also sufficiently good energy resolution. Prompt neutron multiplicities and mass distributionsThe last years have seen the development of many nuclear applications, such as nuclear reactors of 4 th generation, spallation source etc. requiring precise nuclear data for reactions induced by neutrons with energy going up to 20 MeV. Pre-neutron mass and total kinetic energy (TKE) of fragments produced in neutron-induced fission are routinely measured at the European Commission Joint Research Center (EC JRC-IRMM) by means of twin Frisch-grid ionization chambers, where the energy of both fragments is measured. Thanks to the momentum conservation it is possible to infer the pre-neutron mass, but it is necessary to correct for prompt neutron emission. To do this correction, it is assumed that fragments are a

“…Beside the purely experimental interest, recent advances in the theoretical description of prompt emission in fission [8][9][10] require detailed correlation data for verifying the models. The experiment is essentially a reproduction of the experiment performed by Budtz-Jørgensen et al [7] with the traditional analog acquisition system now replaced by a fully digital one and subsequent digital signal processing.…”

Section: Prompt Fission Neutrons From 252 Cf(sf)mentioning

confidence: 99%

Investigating Prompt Fission Neutron Emission from²³⁵U(n,f) in the Resolved Resonance Region

Göök

Hambsch

Oberstedt

2016

Abstract. Investigations of prompt emission in fission is of importance in understanding the fission process in general and the sharing of excitation energy among the fission fragments in particular. Experimental activities at IRMM on prompt neutron emission from fission in response to OECD/NEA nuclear data requests is presented in this contribution. Main focus lies on currently on-going investigations of prompt neutron emission from the reaction 235 U(n,f) in the region of the resolved resonances. For this reaction strong fluctuations of fission fragment mass distributions and mean total kinetic energy have been observed [Nucl. Phys. A 491, 56 (1989)] as a function of incident neutron energy in the resonance region. In addition fluctuations of prompt neutron multiplicities were also observed [Phys. Rev. C 13, 195 (1976)]. The goal of the present study is to verify the current knowledge of prompt neutron multiplicity fluctuations and to study correlations with fission fragment properties.