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

Two types of double confocal waveguide <inline-formula> <tex-math notation="LaTeX">${\mathrm {TE}}_{06}^{anti} $ </tex-math></inline-formula>-mode input couplers operating at 140 and 220 GHz are theoretically and experimentally investigated in this article, respectively. The 140 GHz input coupler is based on a power division network structure, while the 220 GHz input coupler is based on a coaxial resonant cavity structure. The field pattern of these two input couplers are analyzed and discussed. The prototypes were fabricated and tested. Back-to-back transmission experimental results agree well with the results of the theoretical simulations. The experimental results show that the 3 dB bandwidth of the power division input coupler at 140 GHz is about 9 GHz and the maximum transmission is −1.4 dB. The 3 dB bandwidth of the coaxial cavity input coupler at 220 GHz is about 3.5 GHz and the maximum transmission is −0.9 dB. It means that a wider bandwidth can be obtained from the power division input coupler, while a higher conversion efficiency can be obtained fromthe coaxial cavity input coupler. The proposed methodology can be applied to the design of an arbitrary <inline-formula> <tex-math notation="LaTeX">${\mathrm {TE}}_{0{n}}^{\text{anti}} $ </tex-math></inline-formula> (<inline-formula> <tex-math notation="LaTeX">${n} >=2$ </tex-math></inline-formula>) mode input coupler for a double confocal structure gyro-amplifier.

Theoretical and Experimental Investigations on Input Couplers for a Double Confocal Gyro-Amplifier

A Novel Terahertz Frequency Measurement Method Based on the Fabry–Pérot Resonator

A sheet beam electron gun focused by a periodic elliptic magnetic field is designed in this paper. And the periodic elliptic magnetic field has successfully been designed and fabricated. The experimental results show that the measured and the simulated axial magnetic field coincide well.

Design and experiment of the focus system based on periodic elliptic magnetic field

Summary form only given, as follows. Electric pulses are widely used for manipulation of biological cells, for example, cell fusion, rotation, dielectrophoresis, and electroporation. In recent years, the biological effects of ultrashort (/spl sim/ns) electric pulses on cells and tissues were studied and reported. It is obvious that parameters like pulse height, duration, front edge, back edge, and repetition rate, of an electric pulse are all important for biological effects arising from the pulse. There are plenty of experiment studies of the influence of these parameters. We report our analysis and calculation results of the influence of pulse duration. The tendency of our calculation results is consistent with experiment results.

Influence of electric pulse duration on the action on a biological cell

It has been shown that stringent requirements on permeability and permittivity are needed for surface waves to exist on the surface of the vacuum and the medium made from negative-index materials (NIM). In this paper, we theoretically analyzed the transverse magnetic modes on the surface of a finitely thick NIM plate, and examined theoretical predictions with particle-in-cell simulations. The results are in agreement and show that the requirements could be released.

http://ieeexplore.ieee.org/iel7/6847484/6857455/06857691.pdf

Yanyu Wei

Papers

Theoretical and Experimental Investigations on Input Couplers for a Double Confocal Gyro-Amplifier

A Novel Terahertz Frequency Measurement Method Based on the Fabry–Pérot Resonator

Design and experiment of the focus system based on periodic elliptic magnetic field

Influence of electric pulse duration on the action on a biological cell

Study on surface waves in a medium plate made from negative index materials