34 GHz fundamental-mode peniotron for high device efficiency

Summary form only given. The peniotron interaction has been proven capable of yielding electronic conversion efficiency as high as 75%. This inherently high efficiency is due to the nature of the interaction in which the electrons move forward in phase by 360/spl deg/ with each cyclotron orbit. Therefore, the electrons see the transverse component of the resonant wave as a "DC" electric field, experience E/spl times/B drift, and lose all or most of their transverse energy to the wave. However, while high conversion efficiency has been demonstrated, practical application of the peniotron requires that high power be efficiently extracted from the device while competing gyrotron modes are suppressed. This is the objective of the UCD harmonic peniotron. The UCD peniotron incorporates a four-vane slotted cavity with a vane radius of 1.82 mm and slot/vane radius ratio b/a of 1.45. The lowest order mode of this slotted circuit, the /spl pi//2 mode, is a TE/sub 11/-like mode with a large TE/sub 31/ component, which is necessary for the second-harmonic peniotron interaction. This mode is resonant (first axial mode) at approximately 34 GHz for the 31 mm cavity design length. The fundamental-mode interaction provides good separation from possible competing gyrotron modes with the nearest competition being the fourth harmonic gyrotron. Simulation with a large-signal code however, indicates that the starting current of the fourth-harmonic gyrotron mode is above the peniotron operating current of 3.5 amps, further insuring stability. The cavity incorporates diffraction coupling through an output iris to achieve the desired loaded Q of 375 required for overcoupling of the device and maximum power output (approximately 125 kW). The iris output coupling also has the added benefit of heavily loading higher order axial modes, further enhancing stability. VVR-28 ports are coupled directly into the slots of the resonant cavity to allow for power measurement and other diagnostics. Large- signal simulation of the device predicts an electronic conversion efficiency of 58% with a predicted device efficiency of 47%. The device is designed to be driven by a Northrop-Grumman Cusp electron gun.