Analysis of collision cascades in titanium deuteride by D-D fusion

Citation

Workman, Thomas Wilson (1992) Analysis of collision cascades in titanium deuteride by D-D fusion. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/fa6m-mh68. https://resolver.caltech.edu/CaltechETD:etd-08172007-080314

Abstract

As a test of the linear binary collision cascade model for ion-solid interaction, theoretical models of D-D fusion induced by heavy ion irradiation of titanium deuteride are compared with experimental results. Thin-film titanium deuteride samples of composition TiD_1.7 were prepared by heating 320 nm titanium films on silicon dioxide in a static pressure of deuterium. The deuterium content of these films was inferred from changes in the titanium and oxygen contaminant signals measured by 3.05 MeV oxygen-resonance backscattering spectrometry.

The titanium deuteride samples were irradiated with beams of argon and xenon ions with energies ranging from 140 to 600 keV. The energy of the incident ion was transferred to atoms in the sample through a series of nuclear collisions, resulting in deuteron-deuteron collisions with energies up to tens of keV. The cross sections for D-D fusion at these energies are large enough for fusion events to be detected for doses above 10¹⁴ ions. A silicon surface-barrier detector placed at an angle of 130° with respect to the incident ion beam was used to monitor the 3.02 MeV protons and 1.01 MeV tritons from the D(d,p)T reaction and 0.82 MeV ³He ions from the D(d,n)³He reaction. Fusion yields (fusion events per incident ion) ranging from 10^-14 to 10^-10 were measured.

A linear binary collision cascade model is presented which predicts fusion yields which are in excellent agreement with the measured yields for all cases studied. The model predicts a distribution of deuteron-deuteron center-of-mass velocities which causes a distribution of Doppler shifts in the spectrum of the fusion products. The shape of the theoretical proton signals based on the model is a reasonably good fit to the experimental proton signals.

The use of D-D fusion induced by heavy-ion irradiation for measuring deuterium concentrations is compared with currently used methods and is found to be somewhat less sensitive than nuclear reaction analysis, but suitable for measuring deuterium concentrations as low as 2 atomic percent with ion beams producible by ion implanters with an energy range of a few hundred kV.

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