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This paper presents the latest results from a second harmonic gyro-TWA experiment at Strathclyde University. The experiment uses a helically corrugated interaction region and operates at Ka-band. Simulations have been performed to predict the amplifier gain and bandwidth using linear theory. Amplifier stability margin can be improved with the addition of a sever. A sever has been designed and manufactured,...
Latest results from a second harmonic gyro-TWA experiment at Strathclyde University are presented. The Ka-band experiment uses a helically corrugated waveguide. Simulations have been performed to predict the amplifier gain and bandwidth. The simulations are compared to laboratory measurements of the cold waveguide dispersion using a new, improved design of polarization converter.
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...
In a number of applications, wideband amplifiers1–5 provide significant advantages over oscillators of similar output power. For instance, in spherical tokamak fusion plasma heating, frequency agility allows targeted heating of specific plasma layers, possibly providing an additional plasma stabilization technique. Experimental and theoretical investigations of wideband amplifiers at MW power levels...
Centimetre wavelength broadband amplifiers at MW power levels are required for a number of applications including RaDAR as well as spherical tokamak fusion plasma heating and diagnostics. Recent publications1,2,3 on gyro-amplifiers have shown exceptional gain, power, bandwidth and efficiency performance in this wavelength range, however, when larger intrinsic and tunable bandwidths are required, gyro-amplifiers...
A high microwave pulse compressor based on a large diameter 5-fold helical waveguide structure was studied. The eigenwave dispersion was calculated using numerical and analytical techniques and compared with experimental measurements. The results of 5-fold helically corrugated waveguide microwave pulse compression experiments will be presented.
The results of 3-fold helically corrugated waveguide microwave pulse compression experiments are presented. A pulse of 80 ns duration having a power of 5.6 kW is compressed into a 140 kW peak power pulse of 1.5 ns duration. To enhance the power capabilities of the microwave pulse compressor a larger diameter 5fold helical waveguide structure was studied; the eigenwave dispersion is discussed using...
In this paper, we report the observation of high-current (1.5 kA), magnetically confined, annular electron beams with circumference of -220 mm and wall thickness of ~2 mm and its transportation through the 2 m coaxial beam channel with inner/outer radii of 30 mm/40 mm respectively. The results of the experimental studies of a FEM driven by such an electron beam are presented. The results of FEM lasing...
High power millimeter and sub-millimeter wave sources operating in the high GHz - THz (35 GHz-1 THz) frequency range are important for a number of applications. This work will focus on the overview of recent theoretical and experimental research conducted at the University of Strathclyde to design, build and study masers operating at 37.3 GHz, 91.2 GHz and 0.74 THz. The results obtained will be presented...
Waveguide with a helical corrugation of the inner surface has the desirable properties of optimised dispersion, operation far from cut-off and high breakdown field strength which make it an excellent medium for passive pulse compression. New compression measurements at both milli-watt and kilowatt powers using an optimised frequency modulation of the input pulse will be presented and discussed.
Summary form only given. Interference and diffraction of electromagnetic waves on periodic structures is a fundamental topic which has proven to be relevant and applicable to many areas of physics. Periodic structures (also known as Bragg, or photonic band gap structures) have been considered as distributed elements of the interaction space of high power sources of coherent radiation. In this role...
This paper presents an overview of a coaxial free-electron maser (FEM) based on 2D and 1D distributed feedback, driven by a large diameter (70 mm) annular electron beam. Most recent experimental results and numerical simulations are presented and discussed. Particle in cell (PiC) code MAGIC is used to demonstrate the possibility to control the operating mode and frequency of the output radiation....
Waveguides with a helical corrugation on the inner surface have proven an effective dispersive medium for the compression of smoothly frequency modulated microwave pulses. This paper presents the results of experiments where ~5.7 kW, X-band (8.0 GHz - 12.5 GHz), microwave pulses of 67 ns duration and 5% frequency modulation were compressed into 2.8 ns pulses with 12 times higher peak power
Cylindrical waveguide with a helical corrugation on the inner surface has proven an effective dispersive medium for the compression of smoothly frequency modulated microwave pulses. This paper presents the results of experiments where ~5.6kW, X-band (8.0GHz to 12.5GHz), microwave pulses of 80ns duration and 5% frequency modulation were compressed into 1.5ns pulses with 25 times higher peak power
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