Theory of gyro devices with thin electron beams (large-orbit gyrotrons)

It is shown for a precisely aligned electron beam of small thickness in a l arge-orbit gyrotron that high cyclotron harmonics (up to s less than or equ al to 5) can be selectively excited with an electronic efficiency that is a cceptable for some applications (1-10%). When the quality of the electron b eam is high, the selective properties are maintained even for modes with hi gh radial indices, raising hopes that this method can be used to obtain coh erent radiation not only in the millimeter but also in the entire submillim eter wavelength range. A method for taking into account the space-charge ef fects is developed, and it is shown that the corresponding effects can be i mportant at relatively small values of the electron pitch factor. The resul ts of the analysis and preliminary experiments reveal the possibility of cr eating high-power compact sources of submillimeter radiation for the spectr oscopy of various media, the diagnostics of dense plasmas, and some other a pplications. (C) 1998 American Institute of Physics. [S1063-7842(98)01610-9 ].