Repetitively pulsed relativistic klystron amplifier

Levine, Jerrold S.; Harteneck, B.

doi:10.1063/1.112813

Cited by 22 publications

(5 citation statements)

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“…An energy efficienty of 20% and a power efficiency of 35% were obtained for RKA's at the Naval Research Laboratory [6]; similar efficiencies were obtained at Los Alamos National Laboratory [7] and at Physics International [8]. In this Letter we will describe a mechanism that substantially increases the energy efficiency of RKA's to 50%.…”

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confidence: 51%

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Efficient Conversion of the Energy of Intense Relativistic Electron Beams into rf Waves

et al. 1995

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A novel relativistic klystron amplifier has achieved 50%%uo energy efficiency, a significant advance over the previous state of the art of 20%%uo. A radially converging structure that was inserted in the output gap reduced the potential energy residing in the electron beam and maximized rf output energy. Electrons that stopped inside the gap were intercepted by this structure and were shunted to ground. This is in contrast to classical klytons in which such electrons would have formed a virtual cathode and/or flow backward, regaining energy from the rf field.PACS numbers: 85.10.Jz, 41.75.Ht A high current "conventional" klystron amplifier has been considered as a candidate for a high power microwave (HPM) source [1]. However, klystrons that operate with high current are inefficient due to space charge effects and the large spread in the electron energy at the output gap. To reduce these effects a high beam voltage is required. But high voltage leads to beam stiffness that can be overcome only by injecting a high rf input power and/or by lengthening the drift region in klystrons.Relativistic klystron amplifiers (RKA's) use the self-field of annular intense relativistic electron beams (IREB's) to considerably reduce effects associated with beam stiffness [2,3], but the efficiency is still limited by beam loading, rf breakdown, and the spread in the electron kinetic energies at the gaps.During the last year, we have developed a new type of RKA [4] that employs cavities with inductively loaded wide gaps. Using these cavities, we eliminated many deleterious effects that plagued the operation of narrow gap RKA's in the past. However, the energy distribution of the electrons at the output gap could not be narrowed down, leading to inefficient operation.The spread in kinetic energy results from the spatial distribution of the potential energy residing in the IREB and from the bunching mechanism. The particle code MASK [5], which successfully simulated the global operation of RKA's [4], was used to obtain microscopic details of the modulated IREB such as density and energy distributions of the electrons [ Fig. 1(a) -1(d)]. To achieve efficient operation of RKA (or any klystronlike devices), the rf voltage across the output gap has to fulfill two conditions that are impossible to satisfy at the same time, especially for a modulated beam with a large energy spread: (1) It has to be low enough to avoid electron reflection that can cause a virtual cathode formation.(2) It has to be high to drain most of the electrons' energy so as to maximize the RF energy output. An energy efficienty of 20% and a power efficiency of 35% were obtained for RKA's at the Naval Research Laboratory [6]; similar efficiencies were obtained at Los Alamos National Laboratory [7] and at Physics International [8].

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Efficient Conversion of the Energy of Intense Relativistic Electron Beams into rf Waves

et al. 1995

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“…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].…”

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

Kj¹,

et al. 1996

Phys. Rev. Lett.

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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.

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“…Levine and Harteneck at Physics International Corporation reported a repetitively pulsed RKA that produced 250-300 MW peak power at 1.3 GHz in 80-ns pulses at repetition rates of up to 200 Hz. 131 Fazio et al at Los Alamos National Laboratory reported a 500-MW, 1.3-GHz RKA with a FWHM of 0.5 s, using a 600-keV, 5-kA electron beam. 132 The ''super-reltron'' is a klystron-like variant of the conventional vircator that was developed by Titan Advanced Innovative Technologies of Albuquerque, NM ͑see Fig.…”

Section: Relativistic Klystron Oscillators and Amplifiersmentioning

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Review of high-power microwave source research

Gold

Nusinovich

1997

Review of Scientific Instruments

368

138

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This article reviews the state-of-the-art in high-power microwave source research. It begins with a discussion of the concepts involved in coherent microwave generation. The main varieties of microwave tubes are classified into three groups, according to the fundamental radiation mechanism involved: Cherenkov, transition, or bremsstrahlung radiation. This is followed by a brief discussion of some of the technical fundamentals of high-power microwave sources, including power supplies and electron guns. Finally, the history and recent developments of both high-peak power and high-average power sources are reviewed in the context of four main areas of application: ͑1͒ plasma resonance heating and current drive; ͑2͒ rf acceleration of charged particles; ͑3͒ radar and communications systems; and ͑4͒ high-peak power sources for weapons-effect simulation and exploratory development.

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Repetitively pulsed relativistic klystron amplifier

Cited by 22 publications

References 4 publications

Efficient Conversion of the Energy of Intense Relativistic Electron Beams into rf Waves

Efficient Conversion of the Energy of Intense Relativistic Electron Beams into rf Waves

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

Review of high-power microwave source research

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