Low-voltage ubitrons for industrial purposes

Mode-selective amplification in a waveguide free electron laser with a two-sectioned wiggler

“…Consequently, the small signal gain is formulated as (12) If the above equation is specified for the case of a straight wiggler under the conditions of and the gain function becomes (13) Consequently, the small signal gain is reduced to (14) Note that is the total wiggler length in this case. The above gain expression is therefore the same as that derived for conventional waveguide FEL's in [1] and [2].…”

“…For compact FEL's driven by low current electron beams, however, the space charge effects are not important, and the interaction mechanism is dominated by waveguide dispersion with a negligible field variation in the transverse dimensions of the waveguide [1], [2], [4]- [6]. Hence, compact waveguide FEL's may be analyzed in the single-particle regime with both the wiggler field and the radiation field approximated by their on-axis values.…”

“…The electric field of TE mode has one transverse field component on axis given by [2] (1) where is the electron entrance phase with respect to the electromagnetic wave. The wiggler field may be expressed by its on-axis expression (2) (3) for the first and second wiggler sections, respectively.…”

“…This suggests that the waveguide mode may grow at the two resonant frequencies [1], [2], and hence there is a mode competition between the low-frequency mode and the high-frequency mode. Although radiation at high frequency is usually preferred, small signal analysis suggests that the low-frequency mode often has a higher gain than the high-frequency mode [2], [9], [10], as shown in Fig. 2.…”

Strong wiggler field assisted amplification in a second-harmonic waveguide free electron laser

“…Parallel to the efforts to improve the output power at a given electron beam current, an equally important issue in the development of the compact waveguide FEL technology is to reduce the minimum electron energy needed to generate strong radiation at a given frequency [4], [11]- [13]. FEL operations at reduced electron energy not only permit the use of smaller and less expensive power supplies, but also increase the interaction gain indirectly through its inverse proportion to [3], [4].…”