Review of Charged Particle Dynamics. Beam Optics and Focusing Systems Without Space Charge. Linear Beam Optics with Space Charge. Self-Consistent Theory of Beams. Emittance Variation. Beam Physics Research from 1993 to 2007. Appendices. List of Frequently Used Symbols. Bibliography. Index.

Theory and Design of Charged Particle Beams

Homeland security and military defense technology considerations have stimulated intense interest in mobile, high power sources of millimeter-wave (mmw) to terahertz (THz) regime electromagnetic radiation, from 0.1 to 10THz. While vacuum electronic sources are a natural choice for high power, the challenges have yet to be completely met for applications including noninvasive sensing of concealed weapons and dangerous agents, high-data-rate communications, high resolution radar, next generation acceleration drivers, and analysis of fluids and condensed matter. The compact size requirements for many of these high frequency sources require miniscule, microfabricated slow wave circuits. This necessitates electron beams with tiny transverse dimensions and potentially very high current densities for adequate gain. Thus, an emerging family of microfabricated, vacuum electronic devices share many of the same plasma physics challenges that are currently confronting “classic” high power microwave (HPM) generators including long-life bright electron beam sources, intense beam transport, parasitic mode excitation, energetic electron interaction with surfaces, and rf air breakdown at output windows. The contemporary plasma physics and other related issues of compact, high power mmw-to-THz sources are compared and contrasted to those of HPM generation, and future research challenges and opportunities are discussed.

Plasma physics and related challenges of millimeter-wave-to-terahertz and high power microwave generationa)

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: (1) plasma resonance heating and current drive; (2) rf acceleration of charged particles; (3) radar and communications systems; and (4) high-peak power sources for weapons-effect simulation and exploratory development.

/pdf/review-of-high-power-microwave-source-research-4wfh5blzfg.pdf

Review of high-power microwave source research

Fabrication of barium titanate by binder jetting additive manufacturing technology

The achievements resulting from the application of advanced pulsed power to the generation of high power microwaves (HPM) have included the generation of multi-gigawatt pulses of RF energy. The power achievable is orders of magnitude greater than conventional microwave sources can generate. However, the introduction of the HPM technology into logical applications has been limited to date due to the phenomenon of pulse shortening in which the RF pulse terminates before the pulse power source used to produce it. Conventional microwave tubes can generate a few to 10 MW of power with pulsewidths of many microseconds when required. High power microwave sources can produce gigawatts of power, but only for relatively short pulsewidths, typically tens to hundreds of nanoseconds. An international effort during the past few years has generated important new discoveries toward the elimination of pulse shortening. Some of the new techniques have the potential for helping the conventional tube industry as well as being practical for high power microwave sources. This paper reviews the pulse shortening problem, its causes, and the worldwide scope and direction of research conducted to date to resolve it. The paper also discusses the potential remedies for the problem and recommends a course of research to further progress on the issue.

/pdf/evolution-of-pulse-shortening-research-in-narrow-band-high-wzbhfcm6zj.pdf

Evolution of pulse shortening research in narrow band, high power microwave sources

Currently ongoing at Los Alamos National Laboratory is a program to develop high-power, planar 100--300 GHz traveling-wave tubes. A necessary part of this effort is a sheet electron beam source. Previously, we have described a novel asymmetric solenoid lens concept for transforming the circular beam from a high-perveance electron gun to a planar configuration. The lens is a standard electromagnetic solenoid with elliptical, instead of circular, pole apertures. The elliptical pole openings result in asymmetric focusing, which in turn forms an elliptical sheet beam suitable for our planar structures. Here we report the first experimental demonstration of this lens.

/pdf/first-observation-of-elliptical-sheet-beam-formation-with-an-2o8vk0tts0.pdf

First observation of elliptical sheet beam formation with an asymmetric solenoid lens

In this paper, we examine intense space-charge beam physics that is relevant to beam bunching and extraction in a mildly relativistic klystron amplifier, and give numerical examples for a 5 kA, 500 keV electron beam in a 1.3 GHz structure. Much of the peculiar beam physics in these types of devices results from the partitioning of beam energy into kinetic and potential parts. Both tenuous-nonrelativistic and intense-relativistic beams produce effects different in nature from those produced by intense, mildly relativistic beams because the potential energy requirements are either negligible or fixed. In particular, we demonstrate anomalous beam bunching aided by the nonlinear potential requirements and we discuss maximum power extraction as a function of beam bunching. We show that although the space-charge effects can produce quite high harmonic current content, the maximum power extraction from the beam into RF typically occurs at relatively modest bunching. >

Intense space-charge beam physics relevant to relativistic klystron amplifiers

This paper describes the experimental development of a long pulse high current relativistic klystron amplifier (RKA). The desired performance parameters are 1 GW output power and 1 /spl mu/s pulse length with an operating frequency of 1.3 GHz. Peak powers approaching 500 MW have been achieved in pulses of 1 /spl mu/s nominal baseline-to-baseline duration. The half power pulse width is 0.5 /spl mu/s. These pulses contain an energy of about 160 J. RF output rises linearly in concert with the beam current pulse, and terminates abruptly just before the highest part of the pulsed voltage curve is reached. A possible explanation, not yet experimentally confirmed, for the premature termination of the RF pulse is an output cavity gap voltage that is too high, causing electron reflection at the gap and RF breakdown across the gap. A new output cavity has been designed with a much lower shunt impedance and a loaded Q of 4. >

A 500 MW, 1 /spl mu/s pulse length, high current relativistic klystron

We examine beam-cavity interaction physics relevant to mildly relativistic, intense-beam klystron amplifiers. This is an interesting but difficult regime of operation, because of the combination of high beam current and low voltage. The advantage of this regime is that it is relatively easy to access high beam powers (and potentially high microwave output powers) at relatively low beam energy. We calculate the effect of the extremely high beam loading in the input and idler cavities. The output cavity's shunt impedance must match the low beam impedance in order to prevent high output gap voltages that will reflect electrons back upstream. This leads to very low cavity Q factors ( >

Beam-cavity interaction physics for mildly relativistic, intense-beam klystron amplifiers

A gain experiment was performed at Los Alamos using a 120-keV 2-A cylindrical electron beam with a ridged waveguide slow-wave structure at 94 GHz, demonstrating 22 dB of amplification through a traveling-wave interaction. The structure was planar with a gap of 0.75 mm and a length of 5 cm. The 2-A electron beam was confined in a 3.2-kG axial magnetic field, with roughly a 0.5-mm diameter. The electron beam was aligned along the magnetic axis of the solenoid by scribing out its cyclotron motion on a novel optical diagnostic using a procedure that depends on varying the solenoidal field strength. The transport through the structure was verified by letting the beam drill holes in a series of thin metallic foils before insertion of the structure

W.B. Haynes

Papers

First observation of elliptical sheet beam formation with an asymmetric solenoid lens

Intense space-charge beam physics relevant to relativistic klystron amplifiers

A 500 MW, 1 /spl mu/s pulse length, high current relativistic klystron

Beam-cavity interaction physics for mildly relativistic, intense-beam klystron amplifiers

Beam Line Design, Beam Alignment Procedure, and Initial Results for the $W$ -Band Gain Experiment at Los Alamos