Principle and design of a medium-enhanced free-electron laser

Free-electron lasers are widely tunable sources of coherent radiation. The standard vacuum free-electron laser consists of a relativistic electron beam propagating invacuum in a periodic magnetic field. It readily generates infrared radiation using medium energy (50 MeV) electrons. Visible and ultraviolet radiation production requires costly higher energy electrons. This thesis shows that, if a free-electron laser is loaded with a gas, its wavelength of oscillation as determined by phase-matching condition, is shorter than in vacuum for the same electron energy and magnetic field parameters. For example, with a 2.5 cm period, 5kG magnetic field and a 44 MeV electron beam a vacuum free-electron laser would generate 4 micro m radiation, whereas if filled with 0.9 atm of hydrogen gas it would generate 0.25 micro m radiation. The analysis of the gas-loaded free-electron laser (GFEL) is developed following that of the vacuum free-electron laser.