Extraction of 1 GW of rf Power from an Injection Locked Relativistic Klystron Oscillator

Abstract

Initial results of extracted power from a moderately modulated intense relativistic electron beam are reported. The modulation circuit is operated as a relativistic klystron oscillator frequency locked to an external oscillator. A 40% modulated electron beam has yielded more than 1 GW of rms power to a vacuum load and also radiated through an antenna. The ratio of the rf power to the intense electron beam power is approximately 20%.PACS numbers: 84.40.Fe, 07.57.Hm, 41.60.-m A common milestone for all researchers working on high power microwave (HPM) sources has been to extract and radiate rf powers of the order of 1 GW [1][2][3][4][5][6][7]. Many projects also work on providing a long pulse, of order 1 msec, to provide both high power and high energy [1-3]. Many of these efforts have made use of moderate to high voltages (1 MV) at relatively high diode impedances (100 V to 1 kV).We report on an effort to operate at lower impedance and voltage, but with high power and high energy. This has led to complications due to the intense space charge depression of the beam kinetic energy. We began with a Friedman relativistic klystron amplifier (RKA) and converted the system to an injection locked oscillator due to limited power of the external oscillator drive power.This Letter begins with a discussion of the experimental geometry, followed by a discussion of the beam modulation results, and concludes with a brief discussion of extracting and radiating the rf wave.

Equilibrium and confinement of bunched annular beams

“…In this section, we will apply the bunched annular beam equilibrium theory to three experiments, namely, the 1.3 GHz RKA experiment at LANL [1], the 1.3 GHz relativistic klystron oscillator (RKO) experiment at AFRL [2], and the 9.4 GHz backward wave oscillator (BWO) experiment at the University of New Mexico [3]. All three of these experiments utilize an annular electron beam for high-power microwave generation, whose transverse size is comparable to the conductor wall.…”

“…By using density test functions to compute the maximum self-field parameters for annular beams, we compare theoretical parameter limits with those corresponding to three annular beam experiments -1.3 GHz RKA experiment at LANL [1], 1.3 GHz RKO [2] experiment at AFRL, and the 9.4 GHz BWO [3] experiment at the University of New…”

“…In recent years, a number of high-power microwave (HPM) experiments have employed high-intensity bunched annular relativistic electron beams, such as the relativistic klystron amplifier (RKA) experiment at Los Alamos National Laboratory (LANL) [1], relativistic klystron oscillator (RKO) experiment at Air Force Research Laboratory (AFRL) [2], and the backward wave oscillator (BWO) at the University of New Mexico [3]. Since an annular beam typically has a transverse size, which is of the order of the conductor wall radius, the beam-wall interaction can be increased compared to the interaction of a pencil beam with a wall.…”

Optimum energy absorption of a short-pulse laser in a doped dielectric slab

“…One may well wonder whether such greatly enhanced absorption is of the resonant type studied in this paper. Finally we should point out that this model may also be applicable to gas-phase absorption by short pulse laser or even microwave; an example of the microwave source would be a 100 ns microwave pulse at 1.3 GHz, which is equivalent to 130 cycles [9]. …”

Electron beam halo formation in high-power periodic permanent magnet focusing klystron amplifiers

“…Several mechanisms of RF pulse shortening have been proposed [3], ranging from plasma formation at various locations in the device to nonlinear effects at the RF output section [4][5][6][7]. However, few of them have been fully verified in terms of theory, simulation and experiment.…”