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

Science and technologies based on terahertz frequency electromagnetic radiation (100 GHz–30 THz) have developed rapidly over the last 30 years. For most of the 20th Century, terahertz radiation, then referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to 'real world' applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2017, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 18 sections that cover most of the key areas of THz science and technology. We hope that The 2017 Roadmap on THz science and technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies.

The 2016 terahertz science and technology roadmap

Bibliometric data set the scene by illustrating the growth of terahertz work and the present interest in terahertz science and technology. After locating terahertz sources within the broader context of terahertz systems, an overview is given of the range of available sources, emphasizing recent developments. The focus then narrows to terahertz sources that rely on surface phenomena. Three are highlighted. Optical rectification, usually thought of as a bulk process, may in addition exhibit a surface contribution, which, in some cases, predominates. Transient surface currents, for convenience often separated into drift and diffusion currents, are well understood according to Monte Carlo modelling. Finally, terahertz surface emission by mechanical means—in the absence of photoexcitation—is described.

https://iopscience.iop.org/article/10.1088/0022-3727/47/37/374001/pdf

A review of terahertz sources

This paper presents a comprehensive theory of the cyclotron resonance maser (CRM) interaction in a circular waveguide. The kinetic theory is used to derive the dispersion relationships for both TE and TM modes. The TE mode case has been investigated by several authors, but there has been comparatively little work on the TM mode case. However, the TM mode interaction competes effectively with the TE mode interaction at relativistic electron energies. The conditions for maximum temporal and spatial growth rates are shown. The TM mode growth rates are found to vanish when the RF wave group velocity equals the beam axial velocity (‘grazing incidence’). The single particle theory is used to derive a compact set of self-consistent non-linear equations for the TE and TM mode interactions. These equations are particularly appropriate for the cyclotron auto-resonance maser (CARM) regime but applicability extends to other regimes as well. The conditions for optimum efficiency are investigated for oscillator and amp...

Linear and nonlinear theory of the Doppler-shifted cyclotron resonance maser based on TE and TM waveguide modes

We report on hot test measurements of a wide-bandwidth, 220-GHz sheet beam traveling wave tube amplifier developed under the Defense advanced research projects agency (DARPA) HiFIVE program. Nano-computer numerical control (CNC) milling techniques were employed for the precision fabrication of double vane, half-period staggered interaction structures achieving submicrometer tolerances and nanoscale surface roughness. A multilayer diffusion bonding technique was implemented to complete the structure demonstrating wide bandwidth (>50 GHz) with an insertion loss of about −5 dB achieved during transmission measurements of the circuit. The sheet beam electron gun utilized nanocomposite scandate tungsten cathodes that provided over 438-A/cm2 current density in the 12.5:1 ratio sheet beam. An InP HBT-based monolithic microwave integrated circuit preamplifier was employed for TWT gain measurements in the stable amplifier operation region. In the wide-bandwidth operation mode (for gun voltage of 20.9 kV), a gain of over 24 dB was measured over the frequency range of 207–221 GHz. In the high-gain operation mode (for gun voltage of 21.8 kV), over 30 dB of gain was measured over the frequency range of 197–202 GHz. High-power tests were conducted employing an extended interaction klystron.

Performance of a Nano-CNC Machined 220-GHz Traveling Wave Tube Amplifier

Terahertz (THz) electromagnetic (EM) radiation in beam-plasma system under different plasma distribution has been simulated using particle-in-cell (PIC) method in this paper. The calculation results show that the electromagnetic radiation frequency under radially non-uniform plasma distribution is lower than that under uniform plasma distribution, which is good agreement with the theoretical analysis. The related physical analysis about the simulation results is given out. This work will give a better physical understanding of beam-plasma system and provide guidance to the project practice

THz electromagnetic radiation in beam-plasma system under different plasma distribution

In this paper, we have developed an accurate and fast method of predicting the dispersion characteristics, interaction impedance, and attenuation of tunneladder slow-wave structure for millimeter-wave traveling-wave tubes, in which an equivalent circuit theory and the simulations of electromagnetic simulation software are incorporated. The discrepancy between the theoretical data by this approach and the experimental data is within 0.5% on dispersion characteristics. Furthermore, the cold results are used in the nonlinear beam-wave interaction simulation code LATTE to calculate the tube gain. The test results show good agreement with the computer simulated (LATTE) linear and saturated gains.

A Method of Numerical Design of Tunneladder Circuits for Millimeter-Wave Traveling-Wave Tubes

The ridge loaded ring-plane traveling wave tube can provide high output power in a relatively broader bandwidth. The dispersion relation for the interaction between the electron beam and the symmetrical mode propagating in this slow wave circuit is obtained, by means of the Variational method. The method to calculate the arbitrary order Bessel function with complex argument is discussed. The three dimensional trajectory graph of the Bessel function with complex argument is plotted. The instantaneous operating bandwidth can be estimated in terms of the relation between of the gain and frequency.

Computation for the gain of ridge loaded ring-plane traveling wave tube

A planar radial helix slow wave structure based on a low loss medium is suggested Instead of the axial, the beam-wave interaction path of this structure is on the radial direction In this paper, the wave propagation characteristic of the planar radial helix is studied with CST(MWS)

Simulation of a planar radial helix slow wave structure

In this paper, we have proposed a 140 GHz slow-wave structure, consisting of an improved array of half-period-staggered double-vane. This structure is suitable for the millimeter-wave sheet beam traveling-wave tubes (TWTs). Numerical results from HFSS simulations clearly demonstrate that there is the better high-frequency characteristics at frequencies from 130 to 150 GHz for the slow-wave structure.

Yanyu Wei

Papers

THz electromagnetic radiation in beam-plasma system under different plasma distribution

A Method of Numerical Design of Tunneladder Circuits for Millimeter-Wave Traveling-Wave Tubes

Computation for the gain of ridge loaded ring-plane traveling wave tube

Simulation of a planar radial helix slow wave structure

A 140 GHz improved slow-wave structure based on staggered double-vane