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In this paper experimental measurement of a W-band gyrotron travelling wave amplifier (gyro-TWA) which is upgraded to operate at a high output power and wide frequency band will be presented. The gyro-TWA based on helically corrugated interaction region and cusp electron beam source can output a maximum power of ∼5 kW at its centre frequency of ∼94 GHz with an instantaneous frequency bandwidth of...
Two designs of fundamental mode rectangular to circular waveguide TE10 to TE11 mode converter are presented. The waveguide transitions are optimized for operation as an input coupler on a 372 GHz gyro-TWA for Dynamic Nuclear Polarization (DNP) enhancement of NMR imaging. A T-junction input coupler and a multiple hole directional coupler were optimized for operation between 360–384 GHz. The T-junction...
The design of two fundamental mode rectangular to circular waveguide mode converters are presented. The waveguide transitions are optimized for operation as an input coupler on a 372 GHz gyro-TWA for Dynamic Nuclear Polarization (DNP) enhancement of NMR imaging. A T-junction input coupler and a multiple hole directional coupler were optimized for operation between 360–384 GHz. The T-junction coupler...
This paper presents the design and measurement of a HE11 mode multilayer window for a W-band gyro-amplifier. The window acts to seal the vacuum inside the amplifier whilst coupling out microwave power with minimal reflection and absorption. The Gaussian-like HE11 mode is used in order to achieve the lowest reflection through the window. Operating over 90–100 GHz the simulated reflection of this window...
A gyrotron traveling wave amplifier (gyro-TWA) with a cusp electron gun and a helically corrugated waveguide operating in the W-band is presented. When driven by an electron beam of energy 40 keV and current 1.5 A, the simulated microwave output power is 5 kW (CW) with a 3 dB frequency bandwidth of 90–100 GHz and a saturated gain of 37 dB. Linear analyses, numerical simulation and the latest experimental...
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.
The latest experimental results of a W-band (75–110 GHz) gyrotron traveling wave amplifier [1] with a helically corrugated waveguide and cusp electron gun is presented. A waveguide with a helical corrugation on its inner surface has ideal dispersive properties which improve the bandwidth of the amplifier whilst maintaining the already good efficiency of operation [2,3]. The large orbit annular electron...
A quasi-optical corrugated horn has been constructed for a W band gyro-TWA1,2 based on a cusp electron beam source3–5 with a helically corrugated interaction region6–8. The design is intended to provide an effective method to decouple the radiation and the beam so that a depressed collector energy recovery system may be used9–11. The horn converts a cylindrical TE11 mode into a free-space TEM00 mode...
A W-band gyrotron travelling wave amplifier (gyro-TWA) with a cusp electron gun and a helically corrugated waveguide is presented. The large orbit electron beam from the cusp gun interacts resonantly with an ideal eigenwave existing in the interaction region based on the cyclotron resonance maser instability. When driven by the 40 keV, 1.5 A electron beam the amplifier was simulated to output a maximum...
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