RF Breakdown Studies Using a 1.3 GHZ Test Cell

Conference · Fri May 01 04:00:00 EDT 2009

OSTI ID:956737

Sah, R; Johnson, R P; Neubauer, M; Conde, M; Gai, W; Moretti, A; Popovic, M; Yonehara, K; Byrd, J; Li, D; BastaniNejad, M

Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Recent studies have shown that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual vacuum and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. A 1.3-GHz RF test cell with replaceable electrodes (e.g. Mo, Cu, Be, W, and Nb) and pressure barrier capable of operating both at high pressure and in vacuum has been designed and built, and preliminary testing has been completed. A series of detailed experiments is planned at the Argonne Wakefield Accelerator. At the same time, computer simulations of the RF Breakdown process will be carried out to help develop a consistent physics model of RF Breakdown. In order to study the effect of the radiofrequency on RF Breakdown, a second test cell will be designed, fabricated, and tested at a lower frequency, most likely 402.5 MHz.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-07CH11359
• OSTI ID: 956737
• Report Number(s): FERMILAB-CONF-09-206-AD-APC
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
ACCELERATORS
Accelerators
BREAKDOWN
CAVITIES
COMPUTERIZED SIMULATION
ELECTRODES
GEOMETRY
HYDROGEN
MAGNETIC FIELDS
MITIGATION
PHYSICS
TESTING
WAKEFIELD ACCELERATORS