H. Yin

Visualization of a pseudospark-sourced electron beam

A pseudospark (PS)-sourced electron beam of 3-mm diameter has been experimentally investigated. Emission of X-rays was detected during a PS discharge and clear X-ray images were formed using the PS-sourced electron beam impacting on a 0.1-mm-thick molybdenum target at an applied voltage of 46 kV. Using a phosphor-coated scintillator, the beams cross-sectional profile and surrounding ion channel were also observed. These results confirm the presence of an electron beam.

A MEMS fabrication approach for a 200GHz microklystron driven by a small-scaled pseudospark electron beam

High performance terahertz (THz) radiation sources hold great promise for a variety of military and space applications. With micro-electro-mechanical systems (MEMS) fabrication techniques, it is possible to attain the smaller, more precisely machined resonant structures required by Vacuum Electronic Devices (VEDs) to function in these frequencies. The research presented here proposes a design and fabrication process for a micro-klystron with a targeted operating frequency of 200 GHz; being developed jointly by Duke University, the University of Strathclyde, UK, and Logos Technologies. It also analyzes the use of a pseudospark (PS) discharge as a novel electron beam source to drive the klystron. Dimensional tolerances are investigated using both analytic and numeric techniques. The incorporation of alignment structures into the fabrication process that utilize kinematic and elastic averaging effects, along with clever stacking techniques, allows submicron alignment tolerances yielding an expected power output of approximately 5W per klystron with an overall efficiency of 20%. The device proposed here, with a volume on the order of 0.01 cc, should be capable of output power densities of up to 1kW/cc. A fabrication run recently completed at MITs Microsystems Technology Laboratories yielded promising results and 32 silicon die were successfully bonded into a stack 1.4cm tall. Difficulties remain, however, in controlling surface roughness and integrating a klystron with alignment features for parallel processing. Several alternative fabrication schemes have been proposed and another fabrication run based on these modifications is currently underway.

High frequency radiation generation using pseudospark-sourced e-beam

Summary form only given. High frequency radiation sources in sub-terahertz frequency range (0.1–1 THz) are currently very attractive for both research and technical applications. To generate the high frequency radiation, a pseudospark (PS)-sourced electron beam is ideal because of its scalability accompanied with high intensity and high quality beam generation [1, 2]. The propagation of a PS electron beam is aided by an ion channel formed by the beam front resulting in no need for a guide magnetic field, which brings great simplicity and flexibility. Most recently, PS-sourced electron beam experiments were performed with beam diameters in both the millimeter and micro meter range. The 3mm beam was also diagnosed with a beam produced x-ray image. The PS beams have been applied in radiation sources from Ka to W bands [3, 4]. For further radiation generation, a klystron at 94 GHz is designed because the klystron is an ideal choice for higher frequency operation due to its operation mechanism, efficiency and robustness as well as the fact that it may be easily scaled in size as well [5].

Numerical study of pseudospark discharge based electron beam and propagation for terahertz source generation

The Terahertz band of EM spectrum has received considerable research interests recently. A micro-klystron has the potential to meet the requirement of high power and compact terahertz source in many applications. The micro-klystron needs a very thin electron beam with sufficient current density. A pseudospark discharge cathode has the ability to provide high current density with small diameter electron beam (<1mm).

Development of high power broadband gyro-TWAs towards the terahertz range

In this paper gyrotron travelling wave amplifiers (gyro-TWAs) based on helically corrugated interaction regions will be presented. Their operating principle and the first experiment in X-band will be reviewed. The present experiment in W-band using a cusp electron beam source with the capability of a high pulse repetition frequency of 2 kHz will also be presented. The design and performances of the amplifiers for kilowatt output and broadband operation in the millimeter-wave and terahertz frequency ranges will also be presented.

Design of a sub-terahertz oscillator with high output power

Combing the advantages of high beam current density in a pseudospark-sourced electron beam and large beam cross section in a sheet electron beam, the design of a 0.2 THz extended interaction oscillator driven by a pseudospark-sourced sheet electron beam is presented in this paper. An interaction circuit with excellent design performance while at the same time being compatible with conventional manufacturing techniques was achieved. Numerical simulations predicted a radiation power of 1.52 kW even when a relatively high circuit loss is taken into account.

200 GHz BWO experiment with a pseudospark-sourced electron beam

Experimental results are presented of the first successful low-terahertz region operation of a pseudospark-driven backward wave oscillator (BWO) in the frequency range of 140 GHz to 220 GHz. The experiment agrees well with 3D particle-in-cell numerical simulations.

A high-power Ka-band Free-Electron Maser, defined by a 2D – 1D Bragg lasing cavity

Summary form only given. One of the on-going research programs, at the University of Strathclyde, involves the development of high-power, pulsed, Free-Electron Masers (FEMs) with the lasing cavity defined using periodic corrugations on the drift-tube walls1–4. These corrugations form 1D and 2D Bragg resonators, whose reflection bands determine the dominant resonance of the maser5. Proper selection of the FEM undulator magnetic field strength, allows for efficient extraction of energy from a mildly relativistic (400 – 500 keV) electron beam at the resonant frequency of the lasing cavity, leading to monochromatic output at power levels of several tens of megawatts and pulse durations of ∼150ns (determined primarily by the pulse duration of the driving power supply of ∼250ns).

A high-energy pulsed-power supply for high-power microwave sources

Summary form only given. A range of pulsed microwave sources, under investigation at the University of Strathclyde, require the generation of multi-kilo-ampere, relativistic, electron beams1,2. These may be mono-energetic or varying in energy throughout the duration of the pulse (dependant on the source in question), however all require a driving supply capable of dealing with potentially rapid changes in the accelerating diode impedance.

Radiation generation at 94 GHz from a pseudospark-sourced electron beam

A small-scale pseudospark discharge is being investigated as the electron beam source for a klystron operating at a frequency of 94 GHz, and single-gap discharge experiments have been carried out. The klystron has been designed using the particle-in-cell (PiC) code MAGIC-2D and simulated output to date looks promising.