Dymenso (United States)

MPP has recently developed a 50 kW peak power W-band gyro-TWT amplifier with a novel internal mode converter capable of efficiently transforming the TE01 operating mode to a high-quality Gaussian beam over the 92 – 100 GHz frequency band. The gyro-TWT was successfully operated at 48.8 kW peak output powers and duty factors up to 30%. Design details and the results of experimental demonstrations, including infrared images of the output beam, are described below.

Recent advances are presented in the application of the elastic averaging precision alignment methods to the fabrication of W-band serpentine waveguide (SWG) TWT circuits. Previous developments have concentrated on Ka-band circuits [1], fabrication and process developments from these efforts were utilized to optimize the W-band mechanical design and manufacturing process. A W-band circuit consisting of two quasi-symmetrical parts with micron precision micro-machined RF features was joined through a high temperature brazing process. The alignment accuracy of the assembled circuit was evaluated using a scanning coordinate measurement machine (CMM).

We present a study of the effects misalignments have in the assembly of the two halves of a Kaband serpentine waveguide TWT structure using the high frequency electromagnetic simulation software HFSS. The goal of the study is to determine manufacturing tolerances needed in the assembly process. We focus here on the reflected power as a function of frequency from simulations of various misalignments in the plane of the serpentine waveguide's beam tunnel.

Gyrotrons produce power in high-order, transverse electric modes that are typically converted to a Gaussian beam inside the tube. In fusion plasma heating applications, the power is transmitted through a diamond window to an external mirror optical unit where it is coupled into an HE<sub>11</sub> mode in corrugated waveguide. A new coupler is described that couples the cavity RF power directly into corrugated waveguide inside the gyrotron. A high power gyrotron with the improved coupler was tested using 1-MW, 3-μs pulses and demonstrated equivalent power and efficiency as a traditional coupler with HE<sub>11</sub> mode output in corrugated waveguide. In addition, higher HE<sub>11</sub> mode purity was achieved at the gyrotron output.

We report the experimental demonstration of a 5th harmonic mm-wave frequency multiplying vacuum electronic device, which uses an over-moded spherical sector output cavity. In this device, a pencil electron beam is helically deflected in a transverse deflecting cavity before entering the output cavity. No magnetic field is required to focus or guide the beam. We built and tested a proof-of-principle device with an output frequency of 57.12 GHz. The measured peak power was 52.67 W at the 5th harmonic of the drive frequency. Power at the 4th, 6th, and 7th harmonics was 33.28 dB lower than that at the 5th harmonic.

The following topics are dealt with: high-power sources; terahertz emitters; terahertz optics; detectors; quantum cascade lasers; biomolecules; terahertz communications; terahertz cameras; and terahertz spectroscopy systems.