An experimental analysis of the waveguide modes in a high-gain free-electron laser amplifier

Miscellaneous · Sun Jan 01 00:00:00 EST 1989

OSTI ID:5206106

Anderson, B R

The presence, growth, and interaction of transverse waveguide modes in high-gain free-electron laser (FEL) amplifiers has been observed and studied. Using the Electron Laser Facility at Lawrence Livermore National Laboratory, a 3 MeV, 800 A electron beam generated by the Experimental Test Accelerator was injected into a planar wiggler. Power was then extracted and measured in the fundamental (TE{sub 01}) an higher-order modes (Te{sub 21} and TM{sub 21}) under various sets of operating conditions. Horizontal focusing through the wiggler was provided by external quadrupole magnets. There was no axial guide field. The input microwave signal for amplification was generated by a 100 kW magnetron operating at 34.6 Ghz. Power measurements were taken for both flat and tapered wigglers, for two sizes of waveguide, and for both flat and tapered wigglers, for two sizes of waveguide, and for both fundamental and higher mode injection. Mode content was determined by sampling the radiated signal at specific points in the radiation patter. For the flat wiggler and with the large waveguide (2.9 cm {times} 9.8 cm) the power in the higher modes was comparable to power in the fundamental. both exhibited gains greater than 30 dB/m prior to saturation and both reached powers in excess of 80 MW. Choice of injection mode had little effect on the operation of the system. Operation with the smaller guide (WR-229) provided much better mode selectivity. The fundamental mode continued to show optimum gain in excess of 30 dB/m while the higher-mode gain was of order 20 dB/m. As expected, power output increased significantly with the tapered wigglers. The relative mode content depended on the specific taper used.

• Research Organization: California Univ., Davis, CA (United States)
• OSTI ID: 5206106
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
43 PARTICLE ACCELERATORS
FREE ELECTRON LASERS
POWER
ACCELERATORS
AMPLIFICATION
AMPLIFIERS
ELECTRON BEAMS
FOCUSING
GAIN
LAWRENCE LIVERMORE LABORATORY
MAGNETRONS
OPERATION
QUADRUPOLES
WAVEGUIDES
WIGGLER MAGNETS
BEAMS
ELECTRICAL EQUIPMENT
ELECTROMAGNETS
ELECTRON TUBES
ELECTRONIC EQUIPMENT
EQUIPMENT
LASERS
LEPTON BEAMS
MAGNETS
MICROWAVE EQUIPMENT
MICROWAVE TUBES
MULTIPOLES
NATIONAL ORGANIZATIONS
PARTICLE BEAMS
US AEC
US DOE
US ERDA
US ORGANIZATIONS
426002* - Engineering- Lasers & Masers- (1990-)
430100 - Particle Accelerators- Design
Development
& Operation