Tunable fluid-loaded free-electron laser in the low-electron-energy and long-wavelength extreme
نویسندگان
چکیده
A tunable fluid-loaded free-electron laser ~FEL! oscillator is demonstrated. This FEL-type experiment employs low-energy electrons, down to 0.4 keV. Therefore, it interacts with extremely long radio waves, in the VHF range (l.1 m). The device consists of a folded-foil planar wiggler (lW54 cm), and a double-stripline cavity. The variable dielectric loading is implemented by distilled water in glass pipes situated on both sides of the stripline structure. Coherent oscillations are observed at the fundamental cavity mode, around 270 MHz. By varying the fluid dielectric loading, the operating frequency is tuned in a range of 10 MHz. This paper presents ~a! the effect of a variable dielectric loading on the FEL tunability in general, and ~b! an extremely lowelectron-energy and long radiation wavelength, in the lowest end of the known FEL operating spectrum. @S1063-651X~99!03703-4#
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