Prashanth Kumar

A Reflector Antenna for Focusing Subnanosecond Pulses in the Near Field

A prolate-spheroidal reflector antenna focusing subnanosecond pulsed electromagnetic radiation in the near field is studied. This antenna reflector is fed by a pair of balanced, conical-plate transmission lines and the radiated pulse consists of a prepulse, an impulse, and a postpulse. Whereas the prepulse amplitude decreases inversely with distance, the impulse is maximum near the geometric focus, and its power density distribution has a full-width at half-maximum (FWHM) width of 32 cm in the axial direction and 10 cm in the lateral direction.

A Hyperband Antenna to Launch and Focus Fast High-Voltage Pulses Onto Biological Targets

This paper briefly reviews the design of a prolate-spheroidal impulse-radiating hyperband antenna system to launch and focus fast (100 ps) high-voltage ( >; 100 kV) pulses onto biological targets. Design and experiments on a graded five-layer dielectric lens, designed to match the pulses into the target medium, are outlined. The design and numerical simulations of a switch system to launch high-voltage spherical TEM pulses are also presented.

Secondary electron yield measurements from materials with application to collectors of high-power microwave devices

An experimental test facility has been established for measuring the secondary electron yield (SEY) of materials thought to be suitable for low yield vacuum electronic applications such as collectors in high-power microwave (HPM) tubes. Experiments can be broadly divided into two energy-regimes: a high-energy (1-50 keV) and a low-energy (10 eV-1 keV) regime. Measurements of SEY at high energies are presented for the following materials: copper, titanium, and Poco graphite. Observation of time-dependent SEY behavior in these samples suggests that surface processes play an important role during measurements. In addition, SEY at low energies and as a function of the angle of incidence of primary electrons has been measured for plasma sprayed boron carbide (PSBC). The experimental results presented here are benchmarked with existing SEY data in the literature, empirically and to first principle formulae

Radially Inhomogeneous Spherical Dielectric Lens for Matching 100-ps Pulses Into Biological Targets

Design, simulations, and experiments on a radially inhomogeneous spherical dielectric lens, that is used at the second focal point of a prolate-spheroidal impulse radiating antenna, are presented. This lens is designed to match 100-ps pulses into a biological medium. The higher field amplitude and smaller spot size obtained with such a lens are useful for various bioelectric applications.

Launching a fast (100 ps) high-voltage (> 100 kV) pulse into a biological target

This paper describes the design and numerical simulations of a switch system to launch fast (100 ps), high-voltage (>100 kV) spherical TEM waves from the first focal point of a prolate-spheroidal impulse-radiating antenna.

The Dose Effect in Secondary Electron Emission

In this paper, total incident electron dose as an inherent parameter in secondary electron emission is experimentally demonstrated. A completely automated experimental setup allows for measuring of secondary electron yield (SEY) as a function of beam energy, angle of incidence of primary electrons, electron dose, and time. SEY data are presented for copper, plasma-sprayed boron carbide, and titanium nitride samples with principal focus on dose dependence. Experiments were conducted in the low-energy range (5-1000 eV) and direct-current regime. Experimental results have been compared with formulas in literature, and good agreement was observed. Modified empirical formulas incorporating the dose effect have also been proposed.

A prolate-spheroidal impulse-radiating antenna system to launch and focus 100-ps pulses for melanoma treatment

This paper briefly reviews the design of a prolate-spheroidal impulse-radiating antenna system, to launch and focus fast (100 ps) high-voltage (> 100 kV) pulses, as a non-invasive tool for melanoma (skin cancer) treatment. The experiments on a graded five-layer dielectric lens, designed to match the pulses into a biological target medium, are outlined. The design of a switch system to launch high-voltage spherical TEM pulses is also summarized.

A Switched Oscillator as an antenna for high power THz generation

This paper presents an approach to high power THz generation that uses a Switched Oscillator (SwO) as a photoconductively-switched antenna. A simplified model is used to demonstrate the SwO as an effective THz radiator. Numerical simulations are used to optimize various parameters of interest with the primary objective of maximizing the radiated energy and minimizing lossess. The radiation Q and resonant frequency are obtained as function of each parameter.

Carl E. Baum: The University of New Mexico years

This paper reminisces about the final years of Dr. Carl E. Baums life and career as a distinguished Research Professor at the University of New Mexico, Department of Electrical and Computer Engineering. It focuses on Carls most significant research projects during this time, in his capacity as an advisor and mentor to his graduate students, and as a colleague.

Graded dielectric lens to match 100 ps pulses into biological targets

Results from analytical calculations, numerical simulations and experiments for a radially inhomogeneous hemispherical dielectric lens are compared in this paper. Such a lens is used at the second focal point of a prolate-spheroidal impulse radiating antenna to match 100 ps pulses in to biological targets.