Accession Number : ADA326140
Title : Harmonic Millimeter Radiation from a Microwave Free Electron Laser Amplifier.
Descriptive Note : Doctoral thesis,
Corporate Author : COLUMBIA UNIV NEW YORK SCHOOL OF ENGINEERING AND APPLIED SCIENCE
Personal Author(s) : Liu, Yan-Hua
PDF Url : ADA326140
Report Date : JUN 1997
Pagination or Media Count : 91
Abstract : In this project an electron beam is bunched at a microwave frequency and the harmonics of this bunching drive radiation at millimeter wavelengths, using a FEL configured as a single pass traveling wave amplifier. A 10kW 24GHz microwave input signal grows to 200kW level using the lower frequency unstable root of the waveguide FEL dispersion relation. The Columbia FEL facility operates at this frequency in the TE11 mode, using a helical undulator (1.85cm period) and a 3mm dia. 600kV electron beam contained in a 8.7mm ID cylindrical waveguide. The harmonic currents set up by the microwave are found to cause growth of harmonic power under two conditions. When the upper frequency root corresponds to the third harmonic, we observe a small amount of third harmonic emission in the TE11 mode, accompanied by comparable second harmonic. The millimeter harmonic radiation produced is coherent and phase related to the microwave source. Second, we have found substantial emission at the seventh harmonic, most likely in the TE72 mode, which in cylindrical waveguide travels at very nearly the same wave speed as the 24GHz power. In order to excite the seventh harmonic radiation, the electron beam must be displaced from the system axis 2mm in this device. We present a theoretical model of the experiment which predicts that if the microwave signal is strong enough to drive the FEL into saturation, the harmonic radiation becomes powerful.
Descriptors : *HARMONICS, *MILLIMETER WAVES, *FREE ELECTRON LASERS, *LASER AMPLIFIERS, OPTICAL WAVEGUIDES, RESONANT FREQUENCY, ELECTRON BEAMS, GRATINGS(SPECTRA), COHERENT OPTICAL RADIATION, QUANTUM ELECTRONICS, CONTINUOUS WAVE LASERS, DISPERSION RELATIONS, HARMONIC GENERATORS, HARMONIC ANALYSIS, FREQUENCY MULTIPLIERS.
Subject Categories : Lasers and Masers
Radiofrequency Wave Propagation
Distribution Statement : APPROVED FOR PUBLIC RELEASE