ABSTRACT
The magnetron discharge plasma is commonly used in thin film deposition processes, but it can also be utilized for ion beam production. We have developed and investigated an ion source based on planar magnetron discharge. We show that under certain conditions, the discharge, running in a high current pulsed mode, effectively produces plasmas with a high fraction of ions formed from the magnetron target material. The ion beam extracted from the discharge plasma and its composition were studied using a time-of-flight method. The plasma electron temperature was measured by using a double Langmuir probe. We find that the increased working gas pressure and discharge current lower the electron temperature, leading to an increased fraction of target material ions in the plasma and therefore also in the extracted ion beam due to their lower ionization potential compared to that of the working gas.
ABSTRACT
We report on an experimental study of an ion source based on a Penning discharge with a cold hollow cathode in crossed electric and magnetic fields. The minimum vacuum chamber operating pressure was 3 × 10(-5) Torr for argon and 5 × 10(-5) Torr for hydrogen. The use of a hollow cathode allowed decreasing the discharge operating voltage down to 350 V at a discharge current of ~100 mA. At a discharge current of 100 mA and beam accelerating voltage of 2 kV, the ion current was 2.5 mA for argon and 8 mA for hydrogen, and the ion beam on-axis current density 170 and 450 µA/cm(2), respectively. The current-voltage characteristics of the discharge and the radial ion beam current density distribution were measured. The influence of pressure on the discharge parameters and their time stability was investigated.
ABSTRACT
A boron ion source based on planar magnetron discharge with solid boron target has been developed. To obtain a sufficient conductivity of the boron target for high current discharge ignition, the target was heated to the temperature more than 350 °C. To reach this temperature, thermally isolated target was heated by low-current high-voltage magnetron DC discharge. Applying a high-current pulse (100 µs range) provides a self-sputtering mode of the discharge, which generates the boron plasma. Boron ion beam with current more than 150 mA was extracted from the plasma by applying an accelerating voltage of 20 kV. The boron ion fraction in the beam reached 95%, averaged over the pulse length, and the rest ions were working gas (Kr(+)). It was shown that "keeping alive" DC discharge completely eliminates a time delay of pulsed discharge current onset, and reduces the pulsed discharge minimal working pressure.
