A. A. Vikharev

Pulsed cyclic heating of copper surface using high-power 30-GHz free-electron maser

Thermal fatigue of the surface of copper subjected to multiply repeated pulsed microwave heating has been studied in order to estimate the maximum permissible acceleration rate for the CLIC collider at CERN. For this purpose, the damage of copper rings in a test cavity of the JINR-IAP facility was traced under the action of 104–105 microwave pulses at a temperature rise up to 190–250 K in every pulse. The test cavity was loaded by pulses of a high-power 30-GHz free-electron maser. Data on the dynamics of damage developed on the copper surface under the action of a strong electromagnetic field in the cavity are presented.

Millimeter and submillimeter-wave, high-gradient accelerating structures

Accelerating structures to be fed by short rf pulses at room temperatures are considered. Millimeter-wave structures, aimed to obtain more than 150 MV/m gradients at 30-90 GHz, are assumed to be fed by existing multi-megawatt gyrodevices. The highest gradients (~ 100 MV/cm) could be reached using picosecond THz pulses produced by conversion of laser radiation in organic crystals. Using experimental results on THz pulse generation, we suggest a new accelerating structure design.

Efficiency enhancement of active microwave pulse compressors

A microwave pulse compressor operated with a superposition of eigen quasi-degenerated modes is considered. A proper choice of eigen frequencies and Q-factors allows essential reduction of diffraction losses during power storage. Peculiarities of power extraction by means of a high-power RF switch are analyzed. 30 GHz projects of multi-megawatt compressors based on: 1) dual-mode circular cross-section cavity as well as 2) four- mirror cavity with active grating are discussed.