Parametric phase locking in an electron rf oscillator.

We propose a way to achieve phase locking of output rf radiation produced by an oscillator driven by a cw electron beam. The locking mechanism is provided by fast periodic modulation of electromagnetic properties of the operating cavity. Ohmic loss and/or the eigenmode frequency are modulated using induced photoconductivity of a semiconductor insert, as affected by a laser with a pulse repetition rate equal to twice the rf frequency.

Asymmetric bimodal accelerator cavity for raising rf breakdown thresholds.

We consider an axisymmetric microwave cavity for an accelerator structure whose eigenfrequency for its second lowest TM-like axisymmetric mode is twice that of the lowest such mode, and for which the fields are asymmetric along its axis. In this cavity, the peak amplitude of the rf electric field that points into either longitudinal face can be smaller than the peak field which points out. Computations show that a structure using such cavities might support an accelerating gradient about 47% greater than that for a structure using similar single-mode cavities, without an increase in breakdown probability.