W-band Cherenkov maser based on a periodic surface field structure

Summary form only given. The development of periodic structures for use as oscillators and amplifiers in the millimetre and sub-millimetre region has been an important topic in science in recent years [1–4]. The 2D periodic structure used in this instance to form the interaction region has a potential for application in sources of high power microwave and THz radiation [5]. Such a structure can be observed using a hollow, copper, cylindrical waveguide with a sinusoidal grating machined into the walls where the diameter of the waveguide is much larger than λ (D » λ). A surface field is excited around the perturbations if the structure is radiated by a volume field. Normally the surface field created within the structure will propagate with a phase velocity less than c. A relativistic electron beam will travel close to the structure interacting with the surface field as the phase velocity of the EM field can be tuned to be close to the velocity of the electron beam. There will be energy exchange between the two as the electrons give some of their energy to the EM field at the operating frequency of the device. In this paper we demonstrate a novel high Q cavity operating at W-band (75–110GHz), where there is coupling between a near cut-off TM0,6 volume field and an evanescent HE1,20 surface field, produced within a periodic structure. Results will be presented of the numerical modeling of the Cherenkov maser using the PIC code MAGIC. Its viability as a real device, able to produce high power microwave radiation at W-band frequencies, will be discussed.