Phase measurements between a master oscillator and its slave gyroklystron have been made. The pulsed gyroklystron was operated both as an amplifier and as a phase triggered oscillator. As an amplifier, the phase jitter during the 3 πs pulse was 20°; from pulse-to-pulse the jitter was 0.86°. As a phase triggered oscillator the jitter of the firing point from shot-to-shot was < 7° even at input-to-output power ratios as large as 52 dB. The significance of these results for linear accelerator applications Is discussed.

Klystron

10.1109/tns.1985.4334241

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Citations (2)

Influence of Labor Epidural Management on Outcome in Obstetrics

Regional Anesthesia: The Journal of Neural Blockade in Obstetrics, Surgery, & Pain Control (1992)

Robert K. Parker

Labor pain

10.1136/rapm-00115550-199217011-00031

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Citations (3)

Field Emitter Array Development For High Frequency Applications

Robert K. Parker Kevin L. Jensen R.H. Abrams

RF vacuum microelectronics combines the advantages of electron transport in vacuum with gated electron emission structures derived from solid-state microfabrication. The advent of practical gated vacuum emitters of micron size will have a strong impact on RF source technology. Nextgeneration RF amplijiers incorporating microfabricated emitters will allow amplifer designs that minimize the need for high-voltage power supplies, complex modulating circuitry, and the heavy magnets common with linear beam tubes. One attractive application for such eficient compact amplifers is as the vacuum power booster of a microwave power module (MPM), a device that combines a solid-state preamplifer with a low-gain vacuum amplifer for efficiency. Program goals are to create a 50-watt 10-GHz amplifier with 10 dB gain and efficiency exceeding 50%. We will survey the requirements placed on FEAs for per$ormance in a microwave amplifer as determined by various analyses, describe the present status of the pei$ormance of ring cathodes designed for inductive output amplijiers (IOAs), (i.e., the narrow-band, cavity-based klystrode under development at VarianlCPI and the wide-band, helix-based twystrode under development at NRL), and identi! the challenges that remain before this new RF source technology is realized.

Field emitter array

10.1109/ivmc.1997.627395

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Citations (8)

Vacuum electronics at the dawn of the twenty-first century

Proceedings of the IEEE (1999)

V.L. Granatstein Robert K. Parker C.M. Armstrong

In this introduction to the Special Issue on vacuum electronics, the history, operating principles, and recent technological trends of vacuum electronic devices are reviewed. The development of microwave power tubes is described and improvements in these devices over the past quarter of a century are highlighted. These improvements have been substantial and have been driven by modern high-power applications and by advances in materials and computational science. The second part of this paper describes the advent of a new class of vacuum electronics generator as involving relativistic electron beams and interaction with fast waves (e.g., gyrotrons, free-electron lasers). These new types of generators are opening the electromagnetic spectrum beyond the microwave region (i.e., millimeter-wave, infrared, ultraviolet, and even X-ray) for applications of high-power, coherent generators of electromagnetic radiation.

Electromagnetic spectrum

Vacuum tube

Power Electronics

Vacuum ultraviolet

10.1109/5.757251

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Citations (134)

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)

Stents for proximal esophageal cancer: a case-control study

Gastrointestinal Endoscopy (2011)

Robert K. Parker Russell E. White Mark Topazian Robert Chepkwony Sonja P. Dawsey

10.1016/j.gie.2010.11.036

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Citations (28)

Radio-Frequency (RF) Vacuum Electronics: A Resurgent Technology For Tomorrow

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (1987)

Robert K. Parker R.H. Abrams

Recent advances in the development of fast-wave, or periodic-beam, devices operating at millimeter- and submillimeter-wavelengths are not the only signs of resurgence in the field of RF vacuum electronics. Significant progress is being achieved in areas of well-established slow-wave power tube technology. In addition, the field is being stimulated by the introduction of techniques (CADD/CAM and microelectronics fabrication) and technologies (improved magnetics) from other disciplines. By any single-parameter measure -- peak or average power, efficiency, bandwidth noise reduction -- or by more complex figures-of-merit -- power-bandwidth product, Pf2 -- vacuum RF power device performance is advancing, not incrementally, but at breakthrough rates. This dramatic progress could presage a period of growth in RF vacuum electronics unequaled since the postwar period of achievement in magnetron and klystron development.

Vacuum tube

Klystron

Microelectronics

Power Electronics

Traveling-wave tube

10.1117/12.940789

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Citations (4)

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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Citations (0)

Gastrointestinal endoscopy experience of surgical trainees throughout rural Africa

Surgical Endoscopy (2020)

Robert K. Parker Michael Mwachiro Hillary M. Topazian R. Eric Davis Albert F. Nyanga

10.1007/s00464-020-08174-3

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Citations (10)