Cooperation of traveling and quasi-cutoff waves in a cyclotron-resonance maser

Cyclotron radiation cooling of a short electron bunch kicked in an undulator with guiding magnetic field

“…1(b)], namely, is a decreasing function at Ω u > Ω c and an increasing function at Ω u < Ω c [4,14]. We should operate in the region Ω u < Ω c , where electrons with higher input energies get bigger oscillatory velocities (∂V u =∂V ∥ > 0); this is similar to the "negative-mass" effect well known in theory of cyclotron accelerators [15,16] and cyclotron resonance masers [17][18][19][20][21][22][23][24].…”

“…This fact has an evident quantum interpretation, namely, the elementary act of radiation of the wave by a particle is emission of a quant with energy ℏω and axial momentum ℏh, so that δp ∥ =δγ ¼ β gr . Equation (18) leads to the following equation describing the change in the axial electron velocity:…”

“…Moreover, in the case of the cyclotron excitation of a wave with the group velocity comparable with the speed of light, there is one more effect weakening the rf space-charge forces. This is a complicated (helical) spatial structure of the electron bunches [18][19][20][21][22][23][24] caused by rotating character of the excited wave. According to the theory [24], this effect is described also by a factor of ≈γ −2 0 .…”

“…Finally, as compared to the cases of both free-electron and Cherenkov masers, the space-charge parameter in the case of the cyclotron maser is smaller by a factor of γ −4 0 . The second reason to neglect the rf space-charge effects is the "negative-mass" character of these effects [18][19][20][21][22][23][24]. Since the azimuthal bunching is stronger than the axial one, the quasi-Coulomb interaction of electrons leads not to their mutual repulsion (as it happens free-electron and Cherenkov masers) but to their effective phase attraction.…”