Left is one of the first patents on the
multi-cavity magnetron, filed in
Germany in November 29, 1935 by H.E. Hollmann. The patent explains in
explicit detail how the cavity magnetron works and that it can have many
configurations including any even number of cells. Also stated is that a fluid
is used between the outer
magnet and the inner cylinder to cool the device.
is the patent for split-anode magnetron and its controlling circuit. Other
magnetron patents by Hollmann are shown below.