Muons, Inc, Batavia
Old Dominion University, Norfolk, Virginia
LBNL, Berkeley, California
Voss Scientific, Albuquerque, New Mexico
ODU, Norfolk, Virginia
The performance of many particle accelerators is limited by the maximum electric gradient that can be realized in rf cavities. Recent studies have shown that high gradients can be achieved quickly in 805 MHz cavities pressurized with dense hydrogen gas, because the gas can suppress, or essentially eliminate, dark currents and multipacting. In this project, two new test cells operating at 500 MHz and 1.3 GHz will be built and tested, and the high pressure technique will be used to suppress the vacuum effects of evacuated rf cavities, so that the role of metallic surfaces in rf cavity breakdown can be isolated and studied as a function of external magnetic field, frequency, and surface preparation. Previous studies have indicated that the breakdown probability is proportional to a high power of the surface electromagnetic field, in accordance with the Fowler-Nordheim description of electron emission from a cold cathode. The experiments will be compared with computer simulations of the rf breakdown process.
LBNL, Berkeley, California
Funding: This work was supported by the Office of Science, U. S. Department of Energy, under Contract No. DE-AC02-05CH11231.
A fiber-based frequency and timing distribution system based on the principle of heterodyne interferometry has been in development at LBNL for several years. The temporal fiber drift corrector has evolved from an rf-based to an optical-base system, from mechanical correctors (piezo and optical trombone) to fully electronic, and the electronics from analog to fully digital, all using inexpensive commodity fiber components. Short-term optical phase jitter and long-term phase drift are both in the femtosecond range over distribution paths of 2 km and more. The temperature dependence of group and phase velocity correction is measured and applied. We will discuss the results of field tests, integration into various client subsystems and further applications.
