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High-energy plasma immersion ion implantation (PIII) in the range of 50-100 keV is an interesting alternative of surface modification technique to more commonly investigated beam processing of materials in such energies. A stacked Blumlein (SB) technique was used to reach high-voltage pulses of 30 to 100 kV, with much cheaper and electronically simpler configuration compared to a hard-tube (HT) system previously used by another PIII group. The reason is because Blnmlein systems employ cheaper thyratrons with higher current capabilities compared to HT tetrodes. Although HT modulators provide higher retained peak dose and variable pulse duration, Blumlein pulsers are preferable for low-cost systems with lower dose and high-energy implantation. The disadvantages of Blumlein systems are their fixed pulse duration and lower repetition rate ( Index Terms--Aerospace materials, high energy, plasma implantation, surface treatment.

A new method was developed to produce lithium plasma for plasma immersion ion implantation. Initially, an argon glow discharge with operation pressure ranging from 2 x [10.sup.-1] to 1 mbar is generated by negatively polarizing an electrode from -400 to -1500 V. Small pieces of metallic lithium that are 99.9% pure fill the top of a conic crucible, with a depth of 2 cm, in electric contact with the electrode. Argon ions from the plasma are used to bombard this target, where heat is created by the momentum transfer from the impacting ions to the crucible. By controlling the operation pressure and the electrode voltage polarization, it is possible to easily heat the crucible to temperatures above the lithium melting point (180 [degrees]C), causing its evaporation. Lithium atoms are then ionized, mainly due to collisions, with argon ions moving toward the crucible. Double Langmuir probe measurements indicated variation in the density of the discharge from 4 x [10.sup.9] [cm.sup.-3] to [10.sup.10] [cm.sup.-3] after lithium evaporation. Silicon wafer pieces immersed in this mixed plasma were submitted to repetitive negative high-voltage pulses (3 kV/6 [micro]s/2.5 kHz) to accelerate plasma ions. High strain in the treated layers was measured by high-resolution X-ray diffraction. Photoluminescence intensity increased after annealing. X-ray photoelectron spectrometry measurement revealed lithium implantation in silicon with an atomic concentration of 78% on the top surface and a penetration depth of about 75 nm. Index Terms--Lithium, plasma implantation, silicon sample, surface diagnostics.

Blumlein pulsers are well-suited devices for high-voltage pulse generation in nanosecond and microsecond ranges. These generators have been used with great success in several areas such as in breakdown tests, X-ray generation, lasers, and high-energy plasma implantation. They consist of lengths of transmission lines charged in parallel and synchronously discharged in series into the load by using single or multiple switches at the opposite line endings. The main problem with the device performance is the presence of the shield cable impedance contributing to the Blumlein power loss especially when using only one switch. The very well known technique used for minimizing these losses consists of winding the transmission lines to increase the line shielding inductance if coaxial cables are used. Therefore, herein, circuit models are presented to assess theoretically the temporal response of the wound coaxial Blumlein pulsers by using a SPICE circuit simulator. For model assessment, the authors used the experimental results produced by a wound coaxial Blumlein pulser of 100 kV/200 A with 1.0 [micro]s of pulse duration constructed for applications in surface treatment of polymers and aluminum with high-energy ions. Index Terms--Blumlein, coaxial cable, modeling, pulser, SPICE simulator, transmission line.

To treat stainless-steel surfaces by nitrogen plasma implantation, a solid-state compact modulator was devised, in which a 8.0-[micro]F capacitor discharges through a forward converter composed of a low-blocking-voltage insulated-gate-bipolar-transistor switch (1.0 kV) and three step-up pulse transformers, rather than employing hard-tube devices such as in conventional plasma ion implantation pulsers, which are expensive and cumbersome. For this, a modulator was built to produce pulses with amplitudes of the order of 4 kV, duration of about 5.0 [micro]s, and rise time of ~1.0 [micro]s with maximum current/frequencies capabilities of 2.0 A and 5 kHz, respectively. Index Terms--Compact pulser, dc converter, insulated-gate bipolar transistor (IGBT) switch, nitrogen plasma implantation, pulse transformer, surface treatment.

A high-voltage pulsed power supply of 100 kV/200 A with output short pulses of the order of 1 [micro]s (based on stacked coaxial Blumlein technology) was developed for use in surface treatment of materials by plasma implantation. The plasma implantation process requires pulse repetition and the authors' device is capable of operating at a frequency range of 10-150 Hz, depending on the level of the output voltage. Herein, the authors show that nitrogen-ion species were implanted into stainless steel surfaces (SS304) at high energies (> 30 keV) by using this pulser, inducing [alpha] phase as demonstrated by X-ray diffraction diagnostic. Moreover, microhardness tests of these treated samples have shown an improvement of about 13.0% for the surface hardness factor. Index Terms--Blumlein pulser, hardness factor, nitrogen, plasma implantation, stainless steel (SS), surface treatment.

Lumped nonlinear transmission lines (NLTLs) have been studied for the generation of radio frequency (RF) signals in the range of the order of tens of megahertz (MHz) up to a few hundreds of MHz depending on the nonlinear element used in the LC line. The oscillations obtained at the output of these lines are applied in defense mobile platforms and communications systems. Low power NLTLs use varactor diodes as nonlinear elements, which show a strong nonlinear effect with capacitance variation of the order of 90% at their p-n junction with the applied voltage, which is an excellent performance to obtain oscillations at the line output. However, these semiconductor devices operate at low voltage, producing small voltage modulation depth (VMD), low power, and consequently reduced signal range. Looking for increasing the VMD of the signal generated with NLTLs, this work developed a RF amplifier using a metal–oxide–semiconductor field-effect transistor (MOSFET) model RD06HVF1. A 30-section line using varactor diodes MV209 as nonlinear elements can work as an RF source to obtain oscillations with a frequency of 33.3 MHz at the line output. Using SPICE simulations, it has been demonstrated that an amplifier circuit connected to the output of this varactor diode transmission line can produce an increase of the VMD produced at line output from 10.7 to 40 V approximately, thus allowing higher level power to electromagnetic wave propagation and consequently higher signal range. Experimental comparison using a printed circuit board (PCB) prototype with the corresponding simulation will be also shown. [ABSTRACT FROM AUTHOR]

The magnetic suppression of secondary electrons emitted during nitrogen plasma immersion ion implantation is examined. Better suppression in denser plasmas is expected, as the cathode would be maintained if the electron layer were formed faster than it is longitudinally lost.