A compact normal magnet for high power millimeter-wave gyrotrons: The electropermagnet

An innovative compact normal room temperature magnet has been developed for use with millimeter-wave gyrotrons. An example of an electropermagnet has been made and tested to 2.0 T, has a 30 mm ID bore and a 25 mm flat field cavity region, suitable for efficient fundamental and 2nd harmonic mode high power pulse and CW gyrotrons to at least 110 GHz, and is only ~22 kg. Gyrotron design with this magnet for 40 to 100 kWCW, using external high power and depressed collectors, at W-band 94 GHz is discussed. The electropermagnet concept is useful for harmonic cyclotron devices operating at reduced harmonic number for higher efficiency interactions into the submillimeter THz range. This compact concept is expected to fill millimeter-wave portable and size restricted gyrotron type applications where superconducting magnet based systems are not practical. In addition to being very small, other advantages of this magnet are low fabrication cost, negligible operating and maintenance costs, zero standby power, low operating power, fast turn-on time, and no cool-down time.