Experimental study of a 1.5-MW, 110-GHz gyrotron oscillator

This thesis reports the design, construction and testing of a 1.5 MW, 110 GHz gyrotron oscillator. This high power microwave tube has been proposed as the next evolutionary step for gyrotrons used to provide electron cyclotron heating required in fusion devices. A short pulse gyrotron based on the industrial tube design was built at MIT for experimental studies. The experiments are the first demonstration of such high powers at 110 GHz. Using a 96 kV, 40 A electron beam, over 1.4 MW was axially extracted in the design (TE22,6) mode in 3 us pulses, corresponding to a microwave efficiency of 37 %. The beam alpha, the ratio of transverse to axial velocity in the electron beam, was measured with a probe. At the high efficiency operating point the beam alpha was measured as 1.33. This value of alpha is less than the design value of 1.4, possibly accounting for the slightly reduced experimental efficiency. The output power and efficiency, as a function of magnetic field, beam voltage, and beam current, are in good agreement with nonlinear theory and simulations with the MAGY code. In another phase of the experiment, a second tube was built and tested. This tube used the same gun and cavity but also incorporated an internal mode converter to transform the generated waveguide mode into a free-space propagating beam. The gun was tested to full power and current in the experiment. Preliminary results were obtained. A mode map was generated to locate the region of operating parameters for the design mode, as well as for neighboring modes. Scans of the output microwave beam were also taken using a power-detecting diode. Future work will focus on generating high power, as well as operating the collector at a depressed voltage for even higher efficiency. A study is also presented of the 96 kV, 40 A magnetron injection gun.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Anderson, James P. (James Paul), 1972-

Advisor dc:contributor.advisor

• Richard J. Temkin.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/30158

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/30158