Undergraduate Research at Jefferson Lab

Demonstrating Injection Phase Locking of a 915 MHz 75kW Magnetron

Student: Josh Blum

School: J. Sergeant Reynolds

Mentored By: Haipeng Wang

Magnetrons have great potential as highly efficient RF-sources for physics and industry. Many possible applications require a cleaner frequency spectrum than a magnetron typically produces. Using a second, cleaner, RF-source the frequency of a magnetron can be locked, ensuring stability and reducing signal noise. According to the Adler-Chen Model, successful locking depends on the power ratio between injected and magnetron signals and the frequency difference between them. This model has not been proved yet at the target 915 MHz frequency or 75kW power range however. To make sure that the injection signal was not overwhelmed by internal reflections from the high-power magnetron, there was a lengthy tuning and calibration process before running the main experiment. Actual high power tests showed successful phase lock. During these tests sub-Hz level phase locking was demonstrated by reducing current to the magnetron filament. These tests also confirmed that magnetrons have very high efficiency as RF-sources, especially when compared to Klystrons. In the immediate future, these results lead to repeating this process on a second magnetron and then using both magnetrons to demonstrate of power-combining. Success on the next phase of the project will be handed off to industry partners for use in water treatment.

[Watch the presentation on YouTube]