Search results for "Neutron cross section"
showing 10 items of 39 documents
The Generalized Model for the Description of Prompt Neutrons in the Low-energy Fission
2013
Abstract The generalized model for the description of neutron emission from the spontaneous and neutron-induced fission in the energy interval up to 20 MeV is developed. For accurate calculations of nucleon composition and excitation energy of the fissioning nucleus at the scission point, the time-dependent statistical model including the pre-equilibrium neutron emission and nuclear friction effects is used. For each member of the compound nucleus ensemble at the scission point, the primary fission-fragment characteristics such as kinetic and excitation energies and yields are calculated using the scission-point fission model with nuclear shell and pairing effects, and based on the multimod…
MONSTER: a time of flight spectrometer for β-delayed neutron emission measurements
2012
The knowledge of the β-decay properties of nuclei contributes decisively to our understanding of nuclear phenomena: the β-delayed neutron emission of neutron rich nuclei plays an important role in the nucleosynthesis r-process and constitutes a probe for nuclear structure of very neutron rich nuclei providing information about the high energy part of the full beta strength (Sβ) function. In addition, β-delayed neutrons are essential for the control and safety of nuclear reactors. In order to determine the neutron energy spectra and emission probabilities from neutron precursors a MOdular Neutron time-of-flight SpectromeTER (MONSTER) has been proposed for the DESPEC experiment at the future …
Neutron generator for BNCT based on high current ECR ion source with gyrotron plasma heating
2015
BNCT development nowadays is constrained by a progress in neutron sources design. Creation of a cheap and compact intense neutron source would significantly simplify trial treatments avoiding use of expensive and complicated nuclear reactors and accelerators. D-D or D-T neutron generator is one of alternative types of such sources for. A so-called high current quasi-gasdynamic ECR ion source with plasma heating by millimeter wave gyrotron radiation is suggested to be used in a scheme of D-D neutron generator in the present work. Ion source of that type was developed in the Institute of Applied Physics of Russian Academy of Sciences (Nizhny Novgorod, Russia). It can produce deuteron ion beam…
Systematics of neutron emission probabilities from delayed neutron precursors
1973
A simple correlation based on the gross theory ofβ-decay is derived between the neutron emission probabilitiesPn of delayed neutron precursors, theirβ-decay energies and the neutron binding energies of the daughter nuclei. The correlation is shown to be valid for delayed neutron precursors among the fission products. ThePn-values of several expected but still unidentified neutron precursors are estimated together with their contributions to the delayed neutron groups in thermal-neutron induced fission of235U. Some aspects of theβ-strength function for transitions into highly excited states are discussed.
The neutron long counter NERO for studies of neutron emission in the r-process
2010
Abstract The neutron long counter NERO was built at the National Superconducting Cyclotron Laboratory (NSCL), Michigan State University, for measuring β -delayed neutron-emission probabilities. The detector was designed to work in conjunction with a β -delay implantation station, so that β decays and β -delayed neutrons emitted from implanted nuclei can be measured simultaneously. The high efficiency of about 40%, for the range of energies of interest, along with the small background, are crucial for measuring β -delayed neutron emission branchings for neutron-rich r-process nuclei produced as low intensity fragmentation beams in in-flight separator facilities.
Neutron yield from a 13C thick target irradiated by protons of intermediate energy
2007
Abstract Angular and energy distributions of neutrons produced by the interaction of protons of 20, 25 and 40 MeV in 13C targets, in which they are stopped, have been measured by time-of-flight and activation methods. Neutron yields are compared with a Monte-Carlo based model prediction and with the experimental neutron yields of proton and deuteron beams impinging on natural carbon thick targets. The gain with respect to p + 12C is only sizeable at the lowest proton energies. The neutron yield curve of p + 13C versus proton energy is definitely lower than the one of d + 12C, in contrast to the suggestion by an earlier published measurement at 30 MeV.
MONSTER: a TOF Spectrometer for beta-delayed Neutron Spectroscopy
2014
β-delayed neutron (DN) data, including emission probabilities, Pn, and energy spectrum, play an important role in our understanding of nuclear structure, nuclear astrophysics and nuclear technologies. A MOdular Neutron time-of-flight SpectromeTER (MONSTER) is being built for the measurement of the neutron energy spectra and branching ratios. The TOF spectrometer will consist of one hundred liquid scintillator cells covering a significant solid angle. The MONSTER design has been optimized by using Monte Carlo (MC) techniques. The response function of the MONSTER cell has been characterized with mono-energetic neutron beams and compared to dedicated MC simulations.
Large solid-angle polarisation analysis at thermal neutron wavelengths using a 3He spin filter
2002
Abstract The strongly spin-dependent absorption of neutrons in nuclear spin-polarised 3 He opens up the possibility of polarising neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. In this paper we describe the first large solid-angle polarisation analysis measurement using a 3 He neutron spin filter at thermal neutron wavelengths ( λ =2.5 A). This experiment was performed on the two-axis diffractometer D1B at the Institut Laue-Langevin using a banana-shaped filter cell (530 cm 3 ) filled with 3 He gas with a polarisation of P =52% at a pressure of 2.7 bar. A comparison is made with a previous measurement on D7 using a cold neutr…
Accurate Fission Data for Nuclear Safety
2013
The Accurate fission data for nuclear safety (AlFONS) project aims at high precision measurements of fission yields, using the renewed IGISOL mass separator facility in combination with a new high current light ion cyclotron at the University of Jyvaskyla. The 30 MeV proton beam will be used to create fast and thermal neutron spectra for the study of neutron induced fission yields. Thanks to a series of mass separating elements, culminating with the JYFLTRAP Penning trap, it is possible to achieve a mass resolving power in the order of a few hundred thousands. In this paper we present the experimental setup and the design of a neutron converter target for IGISOL. The goal is to have a flexi…
Nuclear Structure Properties of Neutron Rich Ge-Br Isotopes in the Astrophysical r-Process
2006
The astrophysical r-process is responsible for synthesis of roughly half of the elements heavier than iron. In spite of this significance, there are many uncertainties regarding the site of the r-process and the neutron-rich nuclei involved. Studying these nuclei presents a challenge, as they lie far from the valley of stability. Nuclear properties such as β decay half-lives and βdelayed neutron emission probabilities are critical inputs for r-process models. The neutron rich Ge-Br isotopes are in the region just after the N=50 bottle neck in the “classical” r-process, or may serve as seed material for the high entropy neutrino-wind r-process. Neutron rich nuclei play an important role in b…