• E.S.M. McCrory, F.G. Garcia, T.K. Kroc, A. Moretti, M. Popovic
  Fermilab, Batavia

We have been collecting data on the conditioning of the high-gradient accelerating cavities in the Fermilab 400 MeV H-Minus Linac for over 16 years [1]. This linac was upgraded in 1989 from a 201 MHz Alverez structure to include 805 MHz side-coupled cavities. Automated measurements of the sparking rate have been recorded since 1994 and are reported here. The sparking rate has declined since the beginning, but there are indications that this rate may have leveled off now. The X-rays emitted by the cavities are continuing to decrease.

[1] Kroc, et al., Proceedings of LINAC96, pp 338-340

• M. Popovic, A. Moretti
  Fermilab, Batavia
• A. Dudas, R.P. Johnson, M.L. Neubauer, R. Sah
  Muons, Inc, Batavia

Magnetrons are the lowest cost microwave source in dollars/kW, and they have the highest efficiency (typically greater than 85%). However, the frequency stability and phase stability of magnetrons are not adequate when used as power sources for accelerators. Novel variable frequency cavity techniques have been developed to phase and frequency lock the magnetrons, allowing their use for either individual cavities, or cavity strings. Ferrite or YIG (Yttrium Iron Garnet) materials are placed in the regions of high magnetic field of radial-vaned, π−mode structures of a selected ordinary magnetron. A variable external magnetic field that is orthogonal to the magnetic RF field of the magnetron surrounds the magnetron to vary the permeability of the ferrite or YIG material. Measurements of a prototype magnetron will be described.