Direct and Compound-Nucleus Neutrons from 14-18-MeV Protons onBe9,N

Abstract

The angle-integrated experimental (p,xn) spectra, fitted with precompound and evaporation spectra from Griffin's statistical model of intermediate structure, produced g, the number of independent-particle states per MeV, and/,., the compound fraction. For 27 A1, 56 Fe, 11B In, and 181 Ta, g increased linearly with A, from 2 to 13, but decreased to 9dbl for 208 Pb, at 18-MeV proton energy E p . At £ p =14 MeV, g=7=bl for 208 Pb, which may signify vanishing shell effects at large E p . Monte Carlo-type intranuclear-cascade-plus-evaporation calculations yielded spectra and cross sections in agreement with the measurements, allowing for several calculational defects that were made obvious in the comparisons. The Monte Carlo calculations yielded f e values close to those derived by fitting the data with Griffin's calculations for targets heavier than 27 A1. "Nuclear temperatures," obtained from LeCouteur's evaporation analysis for multiple-nucleon emissions, agreed for (p,xn) and giant-resonance (y,xn) reactions, both via the intermediate nucleus 209 Bi, but differed considerably for the target 27 A1, where direct and evaporation neutrons are not well separated in mean energy. The three types of analyses utilized here are therefore much more applicable for heavy nuclei than for light. Energy and angle dependence of (y,xn) reactions indicate negligible direct effects, in sharp contrast to (p,xn) reactions, which display a strong forward anisotropy at the high-energy end of the spectra.

Statistical theory of light nucleus reactions with 1p-shell light nuclei

“…5. The reason is that the 4-mm-thick polyethylene beam stopper in the secondary Faraday cup slightly depresses the yields about 0.5-1.5 MeV at forward angles [6].…”

“…The kerma coefficient describes the kinetic energy of the charged particles released in matter, and expressed [7]. as this equation (6) whereĒ i jk and σ i jk are the average energy (expressed in MeV) and the production cross section (in barns) in the lab system, respectively. Here, idenotes the type of charged particle including light charged particles and recoiling nuclei, j denotes the type of reaction channels, and k indicates the excited energy level of the residual nucleus which can emit the secondary and/or third particle, or proceed via two-body separation, or carry out γ decay.…”

“…At same time, STLN is firstly used to describe 9 Be(p, xn) reaction, and will be extended to describe p+ 6,7 Li reactions in the near future.…”

Development of a PET cyclotron based irradiation setup for proton radiobiology

“…In addition, the Geant4 simulation toolkit [Agostinelli et al, 2003;Allison et al, 2006] (Geant4 version 9.3.p01) with the QGSP_BERT_HP physics package activated was utilized, after validation with published experimental data with protons of similar energy 1 [Verbinski and Burrus, 1969], in order to explain experimental results described in this chapter. Furthermore, Geant4-based Monte Carlo was utilized in order to evaluate the possibility of using one beamline of ICNAS cyclotron for an out-of-yoke irradiation setup.…”

Measurement of neutron energy spectra for Eg=23.1 and 26.6 MeV mono-energetic photon induced reaction on natC using laser electron photon beam at NewSUBARU

“…This assumption will be adequate for relatively heavy nuclei [2], however should be confirmed experimentally for light nuclei due to less population of nucleus. For carbon photo neutron reaction, Noda et al pointed out that an isospin selection rule affects energy dependence of total cross section [3].…”