Active S-Band Pulse Compressor

Pulse compression is a method of increasing the peak power of the microwave pulse at the expense of its length. Pulse compression had been first realized at SLAC, resulting in doubling the energy of the electron beam, hence the name SLED, SLAC energy doubler. Over the years a number of pulse compressors had been demonstrated with some being bulky but efficient, like the binary pulse compressor and other being compact but less efficient, like SLED-II. An active pulse compressor had been proposed to increase the efficiency and compression ratio which relies on a high power active switch. Currently there are no practical switches that can work reliably with 100s of megawatts of power. Most of the switches ferroelectric, plasma-based, semiconductor) are limited by the breakdown strength of various dielectric inserts. An all-metal switch based on relativistic beam has proved to be one of the most successful one. However, this configuration does not seem to be practical for user facility operation. Euclid Beamlabs LLC proposes an active switch that is based on a pure copper resonator and controlled by a single-side multipactor discharge at a metallic wall in the presence of a resonant DC magnetic field and a normal to metal rf field. The discharge is ignited by external rf power produced by inexpensive 2.45 GHz, 1-5 kW magnetrons. In Phase I we will finalize a switch design and manufacture it. We will test the switch operation in the lab. Key characteristics to be demonstrated are the fast time response ~15 ns) and multipactor ignition repeatability. The two-mile accelerator at SLAC utilizes about 200 pulse compressors which are running with about 60% efficiency. Increasing the efficiency to 70% will result in a large energy cost saving. For industrial applications it is even more important to maintain a high efficiency system, because industrial radiography machines often compete with radionuclide gamma irradiators. The end user comparing the electricity bill associated with the accelerator - based system to the cost of securing, servicing and disposing of the radioactive element will find the economics of the pulse compressor accelerator-based source to be extremely favorable. The active pulse compressor will find applications in compact high gradient accelerators.