No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

It was proposed that amorphous alloys may be more resistant to radiation damage than crystalline metals. In crystalline metals neutron induced transmutations lead to the formation of inert gas bubbles. These preferentially nucleate near line defects and result in embrittlement. Amorphous alloys do not contain sites where nucleation can occur preferentially. In this work the growth of argon bubbles in amorphous Cu[50]Zr[50] has been induced by implanting thin specimens with 80keV argon ions at room temperature. The bubble size distribution was obtained over the dose range 5x10[16] to 3x10[17] Ar[+] cm[-2]. Larger bubbles grew in the amorphous alloy than would have been expected to grow in a crystalline metal implanted under the same conditions. It was found that ion bombardment caused surface atoms to be sputtered away from the specimens at a rate of 2.3at.ion[-1]. The sputtering process led to saturation in the amount of argon retained by the material and caused the formation of copper rich near-surface layer. This layer also contained significant amounts of oxygen. Blister formation was induced at the surface of the amorphous alloy by implanting it with 100keV helium ions. At a critical dose of 3x10[17] He[+]cm[-2] a population of very small blisters was formed. These were the result of large bubbles forming just below the specimen surface. As higher doses were used the features joined up to produce large, thin-lidded blisters at a dose of 10[18] He[+] cm[-2]. These observations could not be completely explained in terms of the two popular models of blister formation, where interbubble fracture or lateral stress result in surface deformation.

Measurements of the target thickness dependence of the target x-ray production yield for incident fast heavy ions are reported for thin solid Cu targets as a function of both incident projectile atomic number and energy. The incident ions were F, Al, Si, S, and CI. The charge state of the incident ions was varied in each case to study the target x-ray production for projectiles which had an initial charge state, q, of q = Z₁, q = Z₁ - 1, and q < Z₁ - 1 for F, Al, Si, and S ions and q = Z₁ - 1 and q < Z₁ - 1 for C1 ions. The target thicknesses ranged from 2 to 183 ug/cm². In each case the Cu K x-ray yield exhibits a complex exponential dependence on target thickness. A two-component model which includes contributions to the target x-ray production due to ions with 0 and 1 K vacancies and a three-component model which includes contributions due to ions with 0, 1, and 2 K vacancies are developed to describe the observed target K x-ray yields. The two-component model for the C1 data and the three-component model for the F, Al, Si, S, and C1 data are fit to the individual data for each projectile, and the cross sections for both the target and projectile are determined. The fits to the target x-ray data give a systematic representation of the processes involved in x-ray production for fast heavy ions incident on thin solid targets.

Beginning with its emergence from a high-aspect ratio rectangular aperture, the physics of an intense (current density ≳ 1 mA/cm²), positively charged ion beam is explored in two distinct regions: an electron-free drift region, and a beam plasma containing a large density of space-charge neutralizing electrons. In the drift region, the beam expands due to the mutual inter-ion Coulomb repulsion. Energy, mass, and phase-space density conservation are combined with Poisson's equation to obtain the beam ion density and resulting potential of the diverging beam at any point in 3-dimensional space. Within the beam plasma, the divergence rate is assumed negligible and the beam ion density at the drift/plasma interface taken to be the beam ion density throughout the beam plasma. It is assumed that collisions between beam ions and residual gas molecules, producing a steady generation of electrons and slow residual gas ions, is the dominant mechanism sustaining the beam plasma. Charge is conserved and the energy balance of the plasma examined to obtain the electron and slow-ion densities. Electron, slow-ion, and beam ion densities are then introduced into Poisson's equation to produce a second order partial integro-differential equation requiring a numerical solution. This solution is obtained by expanding the density and potential functions in a complete set of orthogonal (Chebyshev) functions and reducing the differential equation to a system of linear algebraic equations. Calculations in the drift region, for beams of 50, 100 and 500 keV, indicate that all intense beams, regardless of the initial aspect ratio, ultimately relax into the same, near Gaussian profile. In the beam plasma, the theory was applied to a 100 keV, high aspect ratio arsenic beam. The electron density profile is predicted to display a shape similar to that of the beam ions, with the resulting net potential possessing substantial cylindrical symmetry. Both the slow-ion and electron densities and hence the degree of space-charge neutralization, are found to depend strongly on the residual gas density.