Beam conditioning for electron energy recovery systems in devices employing axis-encircling beams
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Date
1988Author
Singh, A.
Lawson, W.
Goutos, D.
Hix, W.
Striffler, C.
Granatstein, V.
Destler, William
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Show full item recordAbstract
Depressed collectors are extensively used in linear-beam devices. In spiraling
beam devices, the motion of the spent beam needs to be converted into axial
motion before it can deliver energy to the retarding axial electrostatic field produced
by depressed collectors. A method of doing so is presented here, along with
simulation results. A large-orbit gyrotron is chosen as an illustrative example in
which the axis-encircling beam is generated by passing an axially streaming beam
through a magnetic cusp. After rf interaction, an 'unwinding' of the beam is done
by a second magnetic cusp with a reversed magnetic field. The trajectories of electrons
going through the two cusps have been simulated in order to evaluate the
effects of finite cusp width and finite width of emitting surface. Also studied are the
effects of variations of the magnetic field, the accelerating voltage of the beam, and
the distance between cusps. These simulations show that the rotational energy of
electrons is largely converted into axial energy after passage through the second
cusp. An initial geometry has been chosen for three collectors, of which two are at
depressed potentials. Changes in the energies of the particles are introduced
between the two cusps as an approximation of the effect of rf interaction. Simulation
of trajectories in the region of the depressed collectors has demonstrated
energy sorting of the beamlets to different depressed collectors.
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