Stalder Technologies and Research

Electrical discharges in liquids can produce plasmas with unusual properties and they have been put to use for a variety of practical applications, including plasma surgery. This photo illustrates a plasma wand operating in a saline solution. The orange glowing region is due to excited sodium atoms. Some other excited-state species, such as OH* are produced, though they are invisible to the naked eye. The bubbles are due to vaporized water shedding off of of the electrically-excited electrode.

At the University of Nevada, Reno, a project funded by the AFOSR was conducted to investigate the properties and methods to produce air plasmas and to investigate methods to minimize the power required to produce such plasmas. This work entailed both computational and experimental work. The top photo at left shows the inside of the tank, with a multipass cell (White Cell) to measure ozone production, and an 8-channel optical emission telescope array for measuring the spatial and temporal evolution of the optical emissions arising from electron-beam excitation.

In a project in the Molecular Physics Lab at SRI International, funded by the Army Research Office, I designed and built a small arcjet plasma device. The feed gas was hydrogen with small admixtures of methane. The arcjet impinged on solid targets, and under certain conditions a polychrystalline diamond film was formed. Diagnostics included optical emission spectroscopy, quadrupole mass spectrometry, Langmuir probes.

Arc plasmas produced by carbon electrodes in helium gas can produce fullerenes (C60, and related carbon molecules). This photo shows the glowing cathode, heated by ion bombardment and the much cooler anode with cathode and anode arcs that are evaporating carbon, from which the fullerenes are produced.

There were significant efforts in the 1980s to produce and study intense relativistic electron beams in air. At SRI, I worked on various contracts at various national laboratories, including LLNL and the Naval Research Lab, using microwave interferometers, laser deflection, and optical emission methods to study plasmas and air channels produced by such beams. These photos are of the Advanced Test Accelerator at LLNL [photos courtesy of Lawrence Livermore National Laboratory]

High power microwave and radiofrequency beams can produce ionization in air, especially at high altitudes. In laboratory experiments at LLNL I applied microwave interferometers to study the temporal behavior of the plasmas produced by high power microwaves. The photo at the left shows the plasma from two different angles, and also shows multiple plasmas formed from reflections off of overdense plasma layers.

From 1983 through 1986 I worked for Applied Materials, Inc., developing new plasma etch tools to process silicon wafers. These early days in semiconductor plasma processing saw the development of the AMAT 8100, AMAT 8300, and AMAT Precision Etch 5000. I am a co-inventor of the magnetically-enhanced plasma reactor at the core of the 5000 series of plasma etchers.

AMAT 8100 multiwafer plasma etcher

Heavy ion fusion is a concept that utilizes high current ion beams to compress fusion fuel pellets to very high densities and temperatures to induce nuclear fusion. The heat released would be captured to produce electricity. Several accelerator concepts were proposed, and some of these are limited by ion-ion charge changing collisions causing loss of beam current. Thus, it was important to determine the cross sections for either charge exchange or ionization, both of which cause beam loss. I built this system to be a target for studies of Cs ion collisions. This was the subject of my Ph.D. thesis.