Boron vacuum-arc ion source with LaB6 cathode.

We describe a pulsed vacuum arc ion source with a lanthanum hexaboride (LaB6) cathode for high-dose selective implantation of 10B and 11B isotope ions. The design and main parameters of the source and its plasma generator are described, and research data are reported on the formation, transport, and magnetic separation of 10B and 11B ions extracted from the erosion plasma of a vacuum arc discharge. Cathode spots are initiated by flashover across an alumina ceramic block of diameter ∼2.5 mm located at the center of the working cathode. The design of the trigger system provides rather uniform cathode erosion, and the cathode dimensions (diameter of 14 mm, length of ∼15 mm) ensure long-term operation of the source. The plasma generator operates at a pulse repetition rate of up to 10 Hz with a discharge current pulse width of 280 µs. At an arc current of 130 A, the source provides an ion beam of a rectangular cross section of 0.6 × 6 cm2 with an energy of 25 keV and amplitude up to 75 mA. A mass analyzer magnet was used for mass-to-charge separation.

Effects of gas pressure and discharge current on beam composition in a magnetron discharge ion source.

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.

Ion source based on a circular anode layer plasma thruster.

A new version of pulsed ion source based on plasma thruster technology has been developed and tested. The ion source design uses a circular anode layer geometry in which the ion beam is extracted radially from the full circumference. The source has been tested for operation in argon, nitrogen, and air at a gas flow rate of up to 20 SCCM with discharge current and voltage measurements in low- and high-current modes. The source, having a simple design and open acceleration gap geometry for observation and photography, is suitable for the treatment of the inner surfaces of pipes and tubes.

Sputtering of pure boron using a magnetron without a radio-frequency supply.

Boron at room temperature is insulating and therefore conventionally sputtered using radio-frequency power supplies including their power-matching networks. In this contribution, we show that through a suitable ignition assistance, via temporary application of a high voltage (∼600 V) to the substrate holder or auxiliary electrode, the magnetron discharge can be ignited using a conventional mid-frequency power supply without matching network. Once the discharge is ignited, the assisting voltage can be reduced to less than 50 V, and after the boron target surface is at elevated temperature, thereby exhibiting sufficient conductivity, the assisting voltage can be turned off. The deposition of boron and boron nitride films has been demonstrated with a deposition rate of approximately 400 nm/h for a power of 250 W.

Surface modification of ferritic steels using MEVVA and duoplasmatron ion sources.

Metal Vapor Vacuum Arc (MEVVA) ion source (IS) is a unique tool for production of high intensity metal ion beam that can be used for material surface modification. From the other hand, the duoplasmatron ion source provides the high intensity gas ion beams. The MEVVA and duoplasmatron IS developed in Institute for Theoretical and Experimental Physics were used for the reactor steel surface modification experiments. Response of ferritic-martensitic steel specimens on titanium and nitrogen ions implantation and consequent vacuum annealing was investigated. Increase in microhardness of near surface region of irradiated specimens was observed. Local chemical analysis shows atom mixing and redistribution in the implanted layer followed with formation of ultrafine precipitates after annealing.

Low-energy dc ion source for low operating pressure.

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.

Boron ion beam generation using a self-sputtering planar magnetron.

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.

A self-sputtering ion source: a new approach to quiescent metal ion beams.

A new metal ion source is presented based on sustained self-sputtering plasma in a magnetron discharge. Metals exhibiting high self-sputtering yield such as Cu, Ag, Zn, and Bi can be used in a high-power impulse magnetron sputtering discharge such that the plasma almost exclusively contains singly charged metal ions of the target material. The plasma and extracted ion beam are quiescent. The ion beams consist mostly of singly charged ions with a space-charge limited current density which reached about 10 mA/cm(2) at an extraction voltage of 45 kV and a first gap spacing of 12 mm.