A.F. Tulinov

The determination of energy losses from the spectrum of particles scattered by a thick target

Abstract A method for determining energy losses from the spectrum of particles scattered by a thick target is presented. By this method the energy losses of protons in Pb, W, Ta, Yb, Ce, Ag, and Mo, and of α-particles to W have been determined. The results obtained agree with the data of other workers and with theory.

Determination of the lifetime of excited compound nuclei in fission using the shadow effect

Abstract The results of three experiments on the observation of the shadow effect in the fission of 238U nuclei in a UO2 single crystal induced by 1.7 and 3.3 MeV neutrons and 25 MeV α-particles are discussed. Comparison is made of the shapes of the fission-fragment angular distributions in the vicinity of two 〈111〉 crystallographic axes directed along and normal to the incident beam. It was found that the displacement of a fissionable nucleus from a lattice site in response to the momentum of the incident particle affects the shape of the shadow. The values of the lifetime of the 239U compound nucleus were found to be (3.5±1.0) × 10−16sec at an excitation energy of 6.5 MeV and (2.0±0.8) × 10−16sec at 8.1 MeV.

Proton energy loss in solids

Abstract The backscattering method is used to measure the 0.1–6.0 MeV proton stopping cross sections. The results obtained are compared with the data published elsewhere and with the Andersen-Ziegler semiempirical curves.

The (α, 2α) reaction on 6Li, 7Li, 9Be and 12C: (I). Experimental data

Abstract The (α, 2α) reaction on 6 Li, 7 Li, 9 Be and 12 C nuclei induced by 25 MeV α-particles was studied by two-dimensional energy analysis. Two-dimensional energy spectra have been obtained at various angular positions of the detectors in the reaction plane. It is shown that for low-filled distributions, the problem of two-dimensional analysis can be reduced to a one-dimensional analysis. The spectra obtained indicate that the (α, 2α) reaction proceeds both through a two-stage channel via known quasi-stationary states of the target nucleus and through a one-stage channel in which all three particles are produced simultaneously. The probabilities of the two processes are comparable; the cross section of the one-stage process decreases with increasing binding energy of the α-particle in the initial nucleus. The α-α angular correlation functions corresponding to the one-stage mechanism have been obtained for symmetrical and asymmetrical arrangements of the detectors with respect to the incident beam.

The determination of energy losses of channeled particles from the backscattering spectra

Abstract A method for determining energy losses o f channeled particles from the backscattering spectra is described. The depth dependence of relative energy losses has been obtained for the (111), , and {110} channels in a tungsten crystal. It has been shown that the depth dependence of the fraction of channeled particles obtained with allowance for energy losses is well described by the exponential law at all depths.

Analysis of the angular dependence of proton energy loss in thin films

Abstract The experimental data on the emergence-angle dependence of 100–400 keV proton energy loss in thin Au foils are reanalysed taking into account the impact parameter dependence of energy loss and the foil thickness inhomogeneity. The results of computer simulations are presented for different theoretical models.

Lifetime-effect relations in the blocking technique for a thick crystal

Abstract The change in blocking dip profiles due to compound nuclei recoil displacement during the lifetime (lifetime-effect relations) has been studied experimentally using the 27Al(p, α) 24Mg resonance reaction at an energy Er=633 keV and treated theoretically using the multistring model and the Fokker-Planck equation. The influence of the crystal thickness traversed by outgoing α-particles and the radiation defects present in the crystal on the lifetime-effect relations has been investigated. The importance of the inclusion of defects in calculations is demonstrated.

Energy loss of protons in Si, Ge and Mo

Abstract From the backscattered energy spectra, the specific energy loss of protons in Si, Ge and Mo in the energy region from 0.1-1.0 MeV has been determined. To eliminate the influence of multiple scattering of protons on the results of the energy-loss determination we have used a slightly modified method from the one discussed by us previously. Absolute energy-loss values for protons in Si, Ge and Mo were determined relative to those in Cu. The results obtained are compared with the data of other authors.

The (α, 2α) reaction on 6Li, 7Li, 9Be and 12C: (II). Theory

Abstract Experimental results obtained for the one-step channel of the (α, 2α) reaction on 6 Li, 7 Li, 9 Be and 12 C at E α = 25 MeV are compared with impulse approximation calculations for the knock-out of an α-cluster from the target nucleus. The effects of going off the mass shell are taken into account; the α-α interaction is described with phenomenological potential parameters deduced from a phase analysis of free α-α scattering. The structure factors are calculated within the framework of the multi-particle shell model with intermediate coupling. For 6 Li, 9 Be and 12 C, satisfactory agreement between theory and experiment is obtained both for the form of the angular correlation functions and for the absolute value of the differential cross section. The assumption of a classical purely “statistical” disintegration of the compound system into three particles without interaction in the final state does not lead to agreement between theory and experiment.

SiC amorphlzation as a result of Ga+ implantation

Abstract The ion implantation of 40 and 90 keV Ga+ ions at high doses into silicon carbide was studied. The thickness of layers randomized by ion implantation determined as a function of the ion dose and energy was compared with that expected from the theory of energy loss in elastic collisons. It was found that the data for two implantation energies could not be described by one value of critical energy deposition. Two factors are proposed to be responsible for the discrepancy: buffer layer formation and beam annealing.