Depressed Collector Experiments On A Quasioptical Gyrotron

A simple, single, single-stage collector has been tested on the quasioptical gyrotron (QOG) experiment at the Naval Research Laboratory (NRL). This is the first application of a depressed collector to a high power gyrotron, and was relatively easily accomplished due to the natural separation of the electron beam and the output radiation in the QOC. Collector efficiencies as high as 50% and overall efficiencies up to 16% were observed. The output power reached 431 kW with an overall efficiency of 13% and a collector efficiency of 41%. The collector efficiency was limited in this experiment due to interception of approximately 15% of the electron beam on an undepressed section of the beam guide, a problem readily correctable with a small change in the beam guide dimensions. If this part of the electron beam was collected at the collector potential, the overall and collector efficiency would increase to 16% and 55% respectively. The maximum collector efficiency would increase to 58% (at high output power) and the best overall efficiency would increase to 20% (at lower output power).

This report presents an update of the experimental achievements published in the review “State- of-the-Art of High-Power Gyro-Devices and Free Electron Masers”, Journal of Infrared, Millimeter, and Terahertz Waves, 41, No. 1, pp 1-140 (2020) and in the KIT Scientific Report 7761 (2021), related to the development of gyro-devices (Tables 2-34). Emphasis is on high-power gyrotron oscillators for long-pulse or continuous wave (CW) operation and pulsed gyrotrons for any applications.

This report presents an update of the experimental achievements published in the review “State- of-the-Art of High-Power Gyro-Devices and Free Electron Masers”, Journal of Infrared, Millime-ter, and Terahertz Waves, 41, No. 1, pp 1-140 (2020) related to the development of gyro-devices (Tables 2-34). Emphasis is on high-power gyrotron oscillators for long-pulse or continuous wave (CW) operation and pulsed gyrotrons for any applications.

The performance of gyrotrons has developed rapidly during recent years and they now form very powerful sources of microwave energy at millimetric wavelengths. Much development, both of the detailed theory including multi-mode interaction and of practical devices, has taken place in the major European laboratories. This book is a collection of surve

The conference proceedings will include the papers of approximately 50 key specialists from most of the world's major fusion laboratories, including the European Community, the U.S., Russia and the PRC. The unifying themes are the emission of electron cyclotron waves by high temperature plasmas and the reciprocal process, absorption, which can be used for heating, non inductive current drive and diagnostic purposes.