• O.A. Ivanov, A.M. Gorbachev, V.A. Isaev, A.A. Vikharev, A.L. Vikharev
  IAP/RAS, Nizhny Novgorod
• J.L. Hirshfield
  Yale University, Physics Department, New Haven, CT
• M.A. LaPointe
  Yale University, Beam Physics Laboratory, New Haven, Connecticut

Funding: Research sponsored by US Department of Energy, Office of High Energy Physics

Experimental investigations of an active Ka-band microwave pulse compressor are presented. The compressor is based on a running wave three mirror quasi-optical resonator utilizing a diffraction grating whose channels embody plasma discharge tubes as the active switch. The principle of compression is based on quickly changing the output coupling coefficient (Q-switching) by initiating plasma discharges in the grating channels. Excitation of the resonator was achieved with a few 100 kW of 34.29 GHz microwaves in 700 nS pulses from the magnicon in the Yae Ka-band Test Facility. A power gain of at least 7:1 in the compressed pulse with a duration of 10-15 nS was achieved.

• S.V. Kuzikov, A.A. Vikharev
  IAP/RAS, Nizhny Novgorod
• J.L. Hirshfield
  Yale University, Physics Department, New Haven, CT
• S. Kazakov
  Omega-P, Inc., New Haven, Connecticut

Funding: Sponsored in part by US Department of Energy, Office of High Energy Physics.

A multi-mode cavity design for a two-beam accelerator aimed to achieve an accelerating gradient exceeding 150 MeV/m is reported. The cavity has a square cross section which allows excitation in several equidistantly-spaced eigen modes by a bunched drive beam in such a way that the RF fields reach peak values only during time intervals that can be much shorter than for excitation of a single mode, thus exposing the cavity surfaces to strong fields for shorter times. This feature is expected to raise the breakdown and pulse heating thresholds. In order to measure an increase in breakdown threshold surface electric field due to this reduction of exposure time during each RF period, a high-power experiment is planned. Preliminary calculations show that such a study in which comparison of breakdown threshold would be made of a conventional single-mode cavity with a multi-mode cavity can in principle be carried out using the drive beam of the CTF-3 test stand at CERN.