V. L. Granatstein

University of Maryland, College Park

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Co-Authors

P. Sprangle

University of Maryland, College Park

John Rodgers

Mississippi State University

Gregory S. Nusinovich

University of Maryland, College Park

Robert K. Parker

Tenwek Hospital

Y. Carmel

Hewlett-Packard (Israel)

W.W. Destler

University of Maryland, College Park

Thomas M. Antonsen

University of Maryland, College Park

W. Lawson

University of Maryland, College Park

K. R. Chu

Institute of Molecular Biology, Academia Sinica

A. K. Kinkead

Clarus Therapeutics (United States)

Cooperative Institutions

University of Maryland, College Park

106

United States Naval Research Laboratory

Massachusetts Institute of Technology

Tel Aviv University

Oak Ridge National Laboratory

Naval Research Laboratory Plasma Physics Division

University System of Maryland

Science Applications International Corporation (United States)

Fusion Academy

Plasma Technology (United States)

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High power microwave sources for advanced accelerators

AIP conference proceedings (1992)

V. L. Granatstein P.E. Latham W. Lawson W. Main M. Reiser

The development of future linear colliders operating at ≳1 TeV center of mass energy will likely depend on the availability of microwave amplifiers which are both affordable and are capable of significantly surpassing the performance of klystrons in terms of power and frequency. One of the most promising concepts for the required amplifiers is the gyroklystron. This paper reviews the physical principles of the gyroklystron and contrasts its phase bunching behavior with that of a klystron. Experiments in a low power gyroklystron which have studied phase noise and penultimate cavity tuning are summarized. The stages in developing an X‐band gyroklystron resulting in the achievement of 29 MW, 1 μsec output pulses with 34% efficiency and 36 dB gain is recapitulated. Finally, plans are described for experiments which will extend gyroklystron performance to the ∼100 MW level at X‐band, and explore operation at a frequency of ∼20 GHz by operating the output cavity at the second harmonic of the electron cyclotron frequency.

Klystron

Harmonic

Center frequency

10.1063/1.42163

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Citations (4)

Realization of a relativistic mirror: Electromagnetic backscattering from the front of a magnetized relativistic electron beam

Physical review. A, General physics (1976)

V. L. Granatstein P. Sprangle Robert K. Parker John Pasour M. Herndon

An intense relativistic electron beam has been injected into a cylindrical drift tube containing a counterstreaming electromagnetic wave ${f}_{i}=9.3$ GHz and ${P}_{i}=170$ kW). Within a narrow range of axial magnetic field centered at 5 kG, a reflected wave at ${f}_{s}\ensuremath{\sim}40$ GHz was generated by the interaction of the beam with the incident wave. The reflected wave was observed to have a power of several hundred kilowatts (i.e., greater than the power of the incident wave) and a pulse duration on the order of nanoseconds. All observed experimental characteristics (viz. frequency shift, power amplification, pulse duration, and cyclotron resonance) were consistent with a model of reflection from the discontinuity in refractive index that is associated with an electron beam front near cyclotron resonance. This mechanism could be employed in a new class of short-pulse, ultrahigh power, tunable generators at millimeter and submillimeter wavelengths.

Relativistic electron beam

Cyclotron resonance

Pulse duration

Electromagnetic pulse

10.1103/physreva.14.1194

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Citations (54)

Gigawatt microwave emission from an intense relativistic electron beam

nrl (1974)

V. L. Granatstein M. Herndon J. A. Nation

Relativistic electron beam

Source

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Citations (2)

Slow Cyclotron Instability in a High-Power Backward-Wave Oscillator

IEEE Transactions on Plasma Science (2004)

Y. Choyal Kazuo Minami V. L. Granatstein

The linear dispersion relation of a backward-wave oscillator (BWO), derived earlier by the authors, is modified to include effects of RF surface current at the beam-vacuum interface. This modified dispersion relation results in an unstable interaction between the slow cyclotron mode (SCM) and the structure mode in addition to the conventional Cherenkov instability caused by the slow space charge mode. Numerical analysis is then carried out using parameters of a BWO experiment at University of Maryland. Fine structure of the SCM instability is elucidated. The analysis indicates that BWO radiation would not be suppressed near cyclotron absorption in an infinitely long system.

Dispersion relation

Backward-wave oscillator

10.1109/tps.2004.835972

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Citations (5)

Can Plasma Microwave Devices Revitalize And Broaden The Scientific And Technological Base Of Microwave Sources?

Y. Carmel Thomas M. Antonsen B. Levush Gregory S. Nusinovich W.W. Destler

The birth of plasma microwave electronics dates back to 1949 when several authors discussed the excitation of electromagnetic waves in a plasma through the beam-plasma instability. Numerous attempts to sue this interaction for the generation and amplification of electromagnetic waves have been only marginally successful, partly because a plasma is a very complicated medium for the propagation of electromagnetic wave, especially when immersed in a magnetic field. Plasma microwave electronics has enjoyed renewed interest and considerable success in the last few years. The authors shall review new results, both in the US and abroad, demonstrating that the presence of a low density background plasma in microwave tubes actually lead to (a) enhanced interaction efficiency, (b) a great reduction or complete elimination of the guiding magnetic field amplitude, (c) high gain, extremely wide band bandwidth amplification, (d) CW operation, and (e) a high degree of spectral purity. Some of these new devices are unique in the sense that their operation is based on hybrid plasma-resonator structures and have no analogue in the field of vacuum microwave devices. The authors plan to discuss future trends, difficulties, and topics open for further investigation.

10.1109/plasma.1994.589116

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A gyrotron-backward-wave-amplifier experiment

S. Y. Park B. Arfin Robert K. Parker V. L. Granatstein J. L. Hirshfield

A proof-of-principle experimental device of a gyrotron backward-wave amplifier has been designed and is being fabricated. The TE 10 -mode device is electronically tunable over 18 to 26 GHz with an instantaneous bandwidth 1 to 3%. The possibility of enhanced bandwidth will be investigated by using a tapered waveguide in a tapered magnetic field.

Gyrotron

10.1109/irmm.1983.9126463

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Axial mode locking in a harmonic-multiplying, inverted gyrotwystron

IEEE Transactions on Plasma Science (2000)

V. L. Granatstein John Rodgers Huaihong Guo G.S. Nusinovich Jie Zhao

When in microwave sources, an open waveguide operating at frequencies close to cutoff is used as a resonator, a number of modes with the same transverse structure, but different axial distribution can be excited by an electron beam. The width of the resonance curves of these modes broadens as the number of axial variations grows. This leads to overlapping of these curves at large axial indexes. As a result, phase locking of such modes may occur. A theory describing axial mode locking in gyrodevices is developed. The results of theoretical analysis are compared to a harmonic-multiplying, inverted gyrotwystron experiment. It is shown that such phase-locked operation in a set of modes with overlapping resonance curves can significantly enlarge the bandwidth of gyrodevices. Furthermore, this technique may be broadly applicable to other devices, which employ cavities with overlapping modes.

Harmonic

10.1109/27.887681

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Citations (11)

High efficiency, phase-locked operation of the harmonic-multiplying inverted gyrotwystron oscillator

IEEE Transactions on Plasma Science (1999)

John Rodgers Huaihong Guo V. L. Granatstein S.H. Chen Gregory S. Nusinovich

The inverted gyrotwystron (phigtron) is a millimeter wave frequency-doubling amplifier that has been demonstrated to produce over 300 kW peak power at twice the input frequency (centered at f/sub in/=16.85 GHz and f/sub out/=33.7 GHz) over a 0.5% bandwidth with a saturated gain of 30 dB and efficiency greater than 35%. The device has also been studied both theoretically and experimentally in a different operating regime where frequency-doubled, phase-locked oscillation is possible. A signal, injected via a fundamental gyro-traveling wave tube input section, modulated a 55 kV, 10 A electron beam. After transit through a drift section, the prebunched electron beam produced phase-locked, second harmonic oscillations in a TE/sub 03/ mode output cavity. RF output centered at either of two frequencies, 34.42 and 34.62 GHz, with a maximum output power of 180 kW, an efficiency of 32% and a locked signal gain of 35 dB was measured. A theoretical prediction of locking bandwidth, a design overview, and the experimental results are presented followed by a summary and discussion of the results.

Frequency multiplier

Harmonic

10.1109/27.772268

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Citations (30)

Axial magnetic field effects on the operation of a millimeter-wave free electron laser

Robert K. Parker R.H. Jackson Steven H. Gold H.P. Freund V. L. Granatstein

Free-electron laser

Extremely high frequency

Free electron model

Source

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Study of an energy recovery system for a large-orbit gyrotron

Ajay Singh W.W. Destler D. Goutos V. L. Granatstein W. R. Hix

An approach to energy recovery from the spent beam of large-orbit gyrotron is outlined that uses a double magnetic cusp arrangement. The first cusp produces a large rotational velocity, while the second cusp unwinds the axis-encircling beam before it proceeds toward depressed collectors. The results of numerical simulations for beam transmission through the two cusps are summarized. An experimental setup for proof of principle is described. Results are presented in the form of the depressed potential on a Faraday cup versus the current collected by it. Current collection is observed up to larger depressed potentials when the second cusp is introduced, as compared with the case where field reversal is not introduced, thus verifying the concept. A design for multiple depressed collectors is presented along with the trajectories in the collector region.< >

Faraday cage

Gyrotron

Orbit (dynamics)

10.1109/iedm.1988.32777

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Citations (3)