No abstract

In the course of developing new high peak power klystrons at SLAC, high electric fields in several regions of these devices have become an important source of vacuum breakdown phenomena. In addition, a. renewed interest in breakdown phenomena for nanosecond pulse, multi-megavoll per centimeter fields has been sparked by recent R&D work in the area of gigawalt RF sourcesThe most important regions of electrical breakdown are in the output c*vjiy gap area, the RF ceramic windows, and the gun ceramic insulator.The details of the observed breakdown in these regions, ex periments performed to understand the phenomena arid solu tions found to alleviate the problems will be discussed.Recently experiments have been performed on a new proto type R&D klystron. Peak electric fields across the output cavity gaps of this klystron exceed 2 MV/cm. The effect of peak field duration (i,e> pulse width) on the onset of breakdown havt-been measured. The pulse widths varied from tens of nanoseconds to microseconds. Results from these experiments will be presented.

It is important to minimize power loss in the waveguide system connecting klystron, pulse-compressor, and accelerator in an X-Band NLC. However, existing designs of klystron output cavity circuits and accelerator input couplers utilize rectangular waveguide which has relatively high transmission loss. It is therefore necessary to convert to and from the low-loss mode in circular waveguide at each end of the system. A description is given of development work on high-power, high-vacuum 'flower-petal' transducers, which convert the TEto mode in rectangular guide to the ml mode in circular guide. A threeport modification of the flower petal device, which can be used as either a power combiner at the klystron or a power divider at the accelerator is also described.