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On the context of the Cern n_TOF collaboration the 232Th(n,2n)231Th reaction cross section has been measured relative to the 56Fe(n,p)56Mn and 27Al(n,a)24Na reaction cross sections by the activation method for neutron energies up to 11 MeV. The neutrons were produced via the 2H(d,n) reaction using a deuterium filled gas-cell, at the 5.5MV TANDEM Accelerator of NCSR "Demokritos". In addition to the experimental work, theoretical Statistical model calculations have been performed using the computer code STAPRE/F. The code STAPRE is designed to calculate energy averaged cross sections for particle induced nuclear reactions with several emitted particles and gamma rays under the assumption of sequential evaporation. For the first evaporation step preequilibrium emission is taken into account while population of states resulting from the first equilibrium evaporation step is calculated using the Hauser-Feschbach theory. Fission process competition is also taken into account in the evaporation steps. Sensitive parameters for the calculation, like level density parameters, have been adopted after fitting experimental data for the competing (n,f) reaction. The results are being compared to the experimental data.

The neutron flux and energy distribution of the neutrons produced in a gas cell were measured using a silicon semiconductor detector. The energy spectra produced by the borbardment of the silicon detector with neutrons were simulated using Monte Carlo techniques and were compared with the measured spectra

A new method is presented for transmission measurements of total neutron cross sections. The detection system has low background with good monitoring of the incident neutron flux and can be used for measurements at En > 5.5 MeV. This method has been applied to total cross section measurements for the system 11B + n at En = 7.3–8.5 MeV. The results show the potential of this method for nuclear spectroscopy measurements of high accuracy.

The cross section of the11B(n, α)8Li reaction has been measured atEn=7.6 to 12.6 MeV. The neutron beam was produced via theD(d, n)3He reaction and aBF3 counter (with naturalB isotopic composition) served both as target for the11B nuclides and as detector for the observation of the delayedα-activity of8Li. The data match well with previous results obtained atEn=12.5 to 20.0 MeV. Using the principle of detailed balance the data were converted to the case of the8Li(α, n0)11B reaction. The associated astrophysicalS(E) factor is dominated by a resonance atER=0.58 MeV of widthΓR =200 keV, withS(ER)=8400 MeV b. ThisS (ER) value for the n0 channel alone is already three times higher than the constantS(E) factor assumed previously and, thus, strengthens the significance of inhomogeneous Big Bang nucleosynthesis.

A new technique for measurements of total neutron cross sections is presented. This method has been applied to measurements of the excitation function for the "B + n system at E = 7.2 - 8.5 MeV, in order to obtain the 8Li(n , 1 B thermonuclear reaction rate. 1. INTRODUCTION In this work, we present a system for transmission measurements of total neutronaoss sectionsusing two silicon semiconductor detectors. One detector is placed in front of the target and monitors the incident neutron flux. The second detector is placed behind the target and measures the attenuation of the incident neutrons as well as their energy.This system has been used to measure the excitation function of the "B(ri. x) reaction , where x is either a neutron or an alpha, and at incident neutron energies between 7.2 and 8.5 MeV.The parameters of the resonances observed in this reaction together with those observed in the previously measured "B(n, a)8 Li reaction2 were used to derive the stellar rate for the 8L i(a, ri)1' B

The deep inelastic reactions of 32S with 27A1 have been studied at incident energies of 152.6 and 175 MeV by measuring inclusive fragment distributions, fragment-fragment and fragment-light particle coincidences. The observed Q-value distributions of the primary deep inelastic process range down to large negative Q-values as predicted by time-dependent Hartree-Fock calculations in the presence of low partial waves. No distinct low-l window for deep inelastic reactions can, however, be inferred from the data.

Energy and angular distributions of neutrons, protons, and alpha particles were measured in coincidence with the projectilelike fragment in deep inelastic collisions of $^{16}\mathrm{O}$ on $^{40,44,48}\mathrm{Ca}$ at 102 and 142 MeV. Using an event-by-event analysis which takes into account particle emission from both fragments and the recoil correction due to light particle emission, we show that our data are consistent with the assumption that the light particles are evaporated in the rest frame of the fully accelerated projectilelike and targetlike fragments. This conclusion is based on the results for neutrons and alpha particles. But because of kinematic limitations which affect the alpha particle data, the conclusions based on the latter are less definitive.