Compact, Inexpensive and High Efficiency Free - Lasers
Free Electron Lasers (FELs) are large and expensive machines because of the high energy electron beam required. FELs are currently limited to national laboratories and universities because of their size and cost limitations. This work is concerned with reducing the size and cost so that an FEL can be placed in an individual investigator's laboratory, allowing the FEL to move to the user instead of the user to the FEL. Efficiency enhancement is also a topic of concern since efficiency is an important parameter in any energy conversion process. A FEL with a component cost, including the accelerator, of approximately 300 k, has lased at 86 μm with a micropulse of approximately 12 ps. The FEL achieved a power growth four orders of magnitude greater than the coherent spontaneous emission with a small signal, single pass gain of 22%. The price is about an order of magnitude less than other FELs for the far infrared, and transforms the device from the role of a national facility to that of a laboratory instrument. Cost reduction was achieved by employing several novel features; a microwave cavity gun for the accelerator, a staggered array wiggler, and an on axis hole in the upstream cavity mirror for electron beam injection and optical radiation extraction. Efficiency is limited in an FEL because as electrons radiate, they lose energy and thus synchronism with the optical wave. A second FEL has been designed to provide high efficiency operation at 10 μm wavelength by means of combining a linear accelerator and magnetic wiggler into one structure. As electrons lose energy to the radiation at the FEL oscillation wavelength, energy is replaced by the microwave linac. The electron beam acts as a catalyst for the conversion of microwave power to infrared power. A six period model of the linac/wiggler was built to experimentally check the microwave properties of the structure. Simulation results predict an efficiency greater than 15% in a 1.35 m long wiggler. A fast variable attenuator will be used to modulate the microwave field in time so that small signal gain reduction is avoided.
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- COST REDUCTION;
- Engineering: Electronics and Electrical; Engineering: System Science; Physics: Optics