Elastic scattering and inelastic excitation of the second, unbound, state 9Be (5/2ˉ, 2.43 MeV) for the identical-particle fermionic system 9Be + 9Be have been measured at the highest incident beam energy presently available ELab(9Be) = 25 MeV. A 9Be beam, produced by the General Ionex Corporation model 860C sputter ion-source, was accelerated by the EN Tandem Van de Graaff accelerator of the iThemba LABS (Gauteng) and was used to bombard a thin 9Be target. The experimental equipment associated with the C-line includes a high resolution ΔE-E gas-ionisation detector coupled to a small scattering chamber. Energy loss and residual energy signals were processed using a CAMAC-based plus OS/2 WIMPS2 data acquisition system running on an online computer. The ΔE-E plots were used to identify the reaction products and their kinematic energies, thereby determining the elastic and inelastic scattering cross-sections. The elastic and inelastic scattering data were analysed in terms of the optical model and Distorted Wave Born Approximation, respectively. Angular distribution data for the elastic scattering for 9Be + 9Be conformed well to the optical model predictions using an energy-independent optical model potential. Inelastic scattering cross-sections were determined up to θc.m.  135° and symmetry effects were investigated. As such, excitation of the second, unbound, state 9Be (5/2ˉ, 2.43 MeV) via a strong E2 one-step two-body interaction from the 9Be (3/2ˉ, g.s.) did not show effects due to symmetry in the entrance channel. These results were consistent with a previous study at ELab(9Be) = 16 MeV.

This study investigates the fusion and scattering of nuclei at energies spanning the Coulomb barrier. The coupling of the relative motion of the nuclei to internal degrees of freedom can be thought to give rise to a distribution of potential barriers. ¶ Two new methods to extract representations of these potential barrier distributions are suggested using the eigen-channel model. The new techniques are based on measurements of quasi-elastic and elastic backscattering excitation functions, from which the representations are extracted by differentiation. A third method utilizing transfer excitation functions is introduced using qualitative arguments. The techniques are investigated experimentally for the reactions 16O + 92Zr, 144,154Sm, 186W and 208Pb. The results are compared with barrier distribution representations obtained from fusion data. The methods are further explored using the systems 40Ca + 90,96Zr and 32S + 208Pb, for which scattering and fusion excitation functions have been measured. The new barrier distribution representations are consistent with the one from fusion. They are direct evidence of the effects of the internal degrees of freedom on channels other than the fusion channel. ¶ The new representations are, however, less sensitive to the barrier distribution compared to their fusion counterpart. This observation is investigated using coupled-channels calculations. They suggest that residual weak reaction channels, which are not included in the coupling matrix, are responsible for the reduction in sensitivity. In the case of quasi-elastic scattering a distortion of the barrier structure above the average barrier is observed. This effect appears to be due to the de-phasing of the scattering amplitudes contributing to each eigen-channel. Using the heaviest system, 32S + 208Pb, it is demonstrated that there is no improvement in sensitivity to the barrier distribution for systems with large Sommerfeld parameters. This suggests that diffraction effects are not likely to be the cause of the sensitivity reduction. ¶ The new techniques may be employed successfully in systems with pronounced barrier structure below the average barrier. This is the case for the reactions 40Ca + 90,96Zr. It is shown that for these systems the quasi-elastic scattering and the fusion representations of the barrier distribution contain the same information. The extracted barrier distributions for the two reactions are distinctively different. They are compared to assess the relative importance of collective excitations and neutron transfer in fusion. Exact coupled-channels calculations show that the distribution for 40Ca + 90Zr arises from coupling of the relative motion to double phonon excitations of 90Zr. Further calculations suggest that the reaction 40Ca + 96Zr involves additional coupling to sequential neutron transfer, which is proposed to be a precursor of neutron-neck formation. ¶ Double phonon excitations are also seen to be important in the system 32S + 208Pb, for which the barrier distribution representations show in addition signatures of one and two neutron transfer.

It has been proposed to use heavy ion beams with energies around 10 MeV/amu, masses around 200, and average charges of 1+ as a driver for inertial fusion reactor. Current designs require the beams to travel through a region where the background gas pressure is several milli-torr. Thus, it is important to assess the rate at which the charge state of an incident beam evolves while passing through the background gas. The first objective of this project is to study the dependence of cross sections for multi-electron loss on target atomic number by using 6 MeV/amu Xe18+ ions and to compare the results with the n-body Classical Trajectory Monte Carlo calculations. A secondary objective of this project is to determine the extent to which the cross sections for molecular targets can be represented as sum of the cross sections for their atomic constituents. Cross sections for loss of one through eight electrons from 6 MeV/amu Xe18+ in single collisions have been measured with noble gas targets. The target Z-dependence of the total loss cross section was found to be well represented by two straight line segments. The cross section for He and Ne define one straight line segment and those for Ar, Kr and Xe define the other, where exhibits a smaller slope. The predictions of n-CTMC calculations are in good agreement with the measured total electron loss cross sections. A semiempirical fitting procedure based on the independent electron approximation provided a reasonably good representation of the individual cross sections for all of the noble gas targets. Additional measurements performed with a variety of molecular targets provided a rigorous test of cross section additivity and showed that the additivity rule works well for electron loss from heavy ions in the present energy and charge regime. A semiempirical calculation based the IEA shows that the average most probable impact parameter for electron loss is much smaller than the target molecular bond length. This result is believed to account for the finding of the insensitivity of the electron loss cross section to molecular structure.

No description available.

Typescript (photocopy) / 94 leaves : Ill., graphs, tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Mathematical Physics, University of Adelaide, 1981

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Experimental measurements in conjunction with stochastic simulations are used to determine hydrogen atom yields in the gamma and heavy ions radiolysis of aqueous solutions of formate and deuterated formate ions. In radiolysis, the hydrogen atom is produced directly by the fragmentation of water excited states, and during the diffusion-kinetic evolution of the radiation track by the intra-track reaction of eaq⁻ with Haq⁺ up to the microsecond timescale. The yield of H• is relatively small, but it is fundamentally very important. An accurate examination of the H atom yields after radiolysis will make possible a better understanding of the initial steps of the radiolytic decomposition of water. The competition between H atom combination reactions and its formation by reaction of eaq⁻ with Haq⁺ makes predictions of the H atom kinetics very difficult. Hydrogen atom yields were determined by difference measurements of H2 yields and directmeasurements of HD yields when using deuterated formate as H• scavenger. While the total H₂ yield measured is always greater for alpha than for gamma radiolysis, the H atom yield is observed to be smaller. The addition of selected scavengers of the hydrated electron and its precursors reveals a stronger correlation of the H atom formation on the precursor to the hydrated electron rather than the hydrated electron itself. Scavengable H• yields strongly decrease as the concentration of the electron scavenger increases. Stochastic track chemistry calculations were used to analyze the measured experimental yields and to elucidate the underlying kinetics.

No description available.

Most of the Generation IV nuclear reactors designs are intended to operate with a fast neutron spectrum. This necessitates further investigation into nuclear fuel behaviour because fast neutrons yield a higher neutron multiplicity with fission fragments, significantly impacting the criticality assessment of these reactors. Current nuclear research conducted at the VElocity foR Direct particle Identification spectrometer (VERDI) is focused on enhancing our understanding of the relationship between fission fragment excitation energy and the compound nucleus, as well as the correlation between excitation energy and neutron multiplicity. This is achieved through the innovative double energy, double-velocity technique (2E-2v). However, time-of-flight measurements face challenges due to the inherent Plasma Delay Time (PDT) resulting from the interaction between ions and Passivated Implanted Planar Silicon (PIPS) detectors. The interacting between fission fragments and the PIPS detectors results plasma, which in turn creates a disturbance in the electric field. This disturbance causes there to be a delay in the electron-holes moving across the surface, resulting in a delay in the timing signal, the PDT.  The purpose is of this study is to parameterize the PDT and explore the amount of information that can be extracted from the pulse shapes of heavy ions using Deep Neural Networks. Moreover, to delve deeper into this phenomenon, an experiment was conducted at Institut Laue-Langevin (LOHENGRIN), and the data from this experiment serves as the foundation for this study. This research demonstrates that it is possible to achieve an accuracy surpassing the timing resolution available at VERDI using data from a single detector. The developed neural network exhibits robustness, translational invariance, and the ability to generalize well across all ion signals. Interestingly, when trained solely on the pulse shape, excluding pulse height information, the network still attains highly satisfactory accuracy. Indicating that the pulse shape already holds ample information. However, further investigations are necessary to enhance the network's ability to generalize across data from multiple detectors.

Usando um modelo de um canal efetivo, o qual contem efeitos de acoplamento de canais através da presença de um potencial de polarização dependente da energia, nós estudamos, em energias abaixo da barreira, as reações de fusão dos sistemas A1 ANTPOT. Ni+ A2 ANTPOT. Ni e 16ANTPOT. O + A ANTPOT. Sm. Com o auxilio de uma relação de dispersão inversa, obtivemos a parte imaginária desse potencial em termos da parte principal da integral envolvendo a parte real do mesmo. A consistência deste método foi verificada através da comparação entre este potencial empírico e o potencial de polarização efetivo determinado a partir de um acoplamento específico de canais. Foram também calculados o primeiro e segundo momentos da distribuição de momentos angulares da seção de choque parcial de fusão. / Using an effective one channel model which contains channel coupling effects through the presence of an inclusive energy dependent polarization potential, we studied sub - barrier fusion of the systems A1Ni + A2Ni and 16O+ASm . With the aid of an inverse dispersion relation, we obtained the imaginary part of this potential. The consistency of this method is c hecked by comparing this empirical polarization potential with the one determined from the explicit consideration of a specific channel coupling. The first and the second moments of the angular momentum distribuition of the partial fusion cross-section were calculated also.