Al Ion Beam Research Articles

Aluminum Ion Beam Treatment of Zirconium Ceramics

The paper presents the radiation and thermal treatment of zirconium ceramics with high-energy Al ion beams generated at an accelerating voltage of 1.5 kV, which modifies the structure and electrophysical properties of zirconium ceramics. Compact powder and ceramic samples are used for the radiation and thermal treatment performed at 1123–1173 K. The surface treatment of compact powders leads to the increase in the grain size, whereas the surface of ceramic samples turns black and electrically conductive in depth. This is because the change in the oxygen stoichiometry of zirconium ceramics. Air annealing of treated ceramics returns the sample to the initial state. The phase composition, microhardness and density of ceramic samples display no changes after the radiation and thermal treatment. Under the experimental conditions, the diffusion of aluminum ions in the surface layer is not observed. It is found that the ion beam treatment leads to the decrease in aluminum-containing impurity in the surface layers of zirconium ceramics.

Measurements of gross erosion of Al in the DIII-D divertor

Aluminum (Al) is a convenient proxy for beryllium (Be) plasma material interaction studies since they have a number of physical and chemical similarities. Al samples were exposed at the lower outer strike point of an L-mode divertor plasma in DIII-D (conditions 7–11×1018 D-ions cm−2s−1, Te=12–47eV). The gross erosion rate was directly measured using post-mortem ion beam analysis of small 1mm-sized samples where local re-deposition was determined to be negligible. The gross erosion rate was also calculated using spectroscopic methods, but these rates greatly underestimate the direct (i.e. non-spectroscopic) measurement. The direct measured erosion yields were within the range of published D+→Al ion beam sputtering yields. The ionizations per photon (S/XB) coefficients used in the spectroscopic analysis were determined in separate experiments using He plasmas at the PISCES-B linear plasma facility at UCSD. The measured S/XB coefficients were on average ∼6× higher than the theoretically calculated values.

Release of Al from SiC targets used for radioactive ion beam production

On-line targets of silicon carbide have been used to produce radioactive ion beams (RIB) at TRIUMF’s ISAC facility. Surface ionized beams of Li, Na and Al from SiC targets have been delivered to a variety of experiments. While yields of Li and Na radionuclide beams have been high enough to meet experimental requirements, the yields of radio-aluminums have been very low in comparison to in-target production estimates. The properties of SiC relevant to radioactive Al ion beam production are reviewed and on-line measurements of radiogenic Li, Na and Al from SiC are presented. Diffusion, effusion and formation of stable phases are found to strongly affect the release of radio-aluminum from SiC, greatly reducing overall Al RIB production efficiency. In comparison, the production of radio-sodium beams from SiC is found to be relatively efficient.

Growth of Epitaxial Al2O3 Films on Silicon by Ionized Beam Deposition

AbstractEpitaxial Al2O3 films have been successfully grown on an oxidized silicon substrate by the ionized beam deposition using an Al ion beam in oxygen environments. The crystalline quality dependence of the Al2O3 films on the growth temperatures was investigated. Using in situ reflection high energy electron diffraction, the orientation relationships between epitaxial Al2O3 films and Si substrate were found to be (100) Al2O3//(100) Si with [110] Al2O3//[110] Si and (111) Al2O3//(111) Si with [112] Al2O3//[112] Si. The stoichiometry of the films was found to be similar to that of sapphire from XPS measurements.

Extraction characteristics of a high current metal ion source

A metal ion source has been developed for extracting high current ion beams of high melting point metals. In the discharge chamber, metal vapor was confined in high-temperature shields, and the pure metal plasma was produced by the arc discharge. In order to prevent the vapor deposits, the extraction electrodes were also required to be high temperature. Thus, multislit electrodes were improved to maintain fine beam optics even if they were heated. To investigate the metal ion extraction characteristics, Al ion beams were extracted and compared with Ar ion beams. Furthermore, high current Al, Cr, Si, and Ti ion beams were extracted, and the extracted current ≳100 mA was obtained for each metal.

High-current metal ion beam extraction from a multicusp ion source

Improvements have been made in a multicusp ion source, which made it possible to produce metal–vapor plasma and extract a high-current metal ion beam. In the discharge chamber, double radiation shields were set and the inner shields were heated to 1860 K. Therefore, it became possible to maintain enough metal–vapor density to produce plasma without the use of support gas. For the extraction of a high-current metal ion beam, we used multislit electrodes in the accel–decel electrode structure. Experiments of the metal ion beam extraction were performed with several kinds of metals (Al, Cr, Si). For example, the extracted Al ion beam current reached 65 mA. As a result of mass analysis, it was found that more than 90% of an Al ion beam is Al+. Furthermore, stable operation could be achieved. For Al (58 mA) and Si (28 mA) ion beam extraction, the temporal drift of each ion beam current was within ±5% for 3 h.

Reservoir-type liquid metal ion source of Al

A liquid metal ion source of Al with a boride reservoir was developed. In this reservoir a shorter boride emitter was designed to overcome the brittleness of boride materials and some problems in supplying the Al material. This source makes possible a long continuous operation time and enhanced reliability. The fundamental performance characteristics did not change after 250 h of operation. A stable Al ion beam emission was obtained for more than 500 h and its current fluctuation was less than ±1%/3 h for a 20–30-μA source ion current. The energy spread was less than 9 eV (FWHM) for a 30-μA/sr angular current intensity.