Vg. Kurakin, HIGH-CURRENT RACETRACK MICROTRON AS A FREE-ELECTRON LASER DRIVER, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 341(1-3), 1994, pp. 407-411
A racetrack microtron combines the best features of a linac and a clas
sical microtron. It might serve as a basis for free electron lasers to
make these promising devices more compact and relatively cheap and th
us available for many laboratories. At the same time it is known that
stable acceleration in a racetrack is broken up at high intensity by a
utomodulation of the beam current. It is shown in this paper that such
modulation originates from positive feedback arising at some frequenc
ies between the system rf cavity and the electron beam. The beam-cavit
y interaction equations followed by a stability analysis are presented
. A linear approximation is used to derive stability conditions, the l
atter being represented in an analytical form followed by numerical ca
lculations and a stability diagram. Comparing the results obtained wit
h experimentally measured values shows the validity of the approach us
ed. The physical meaning of observed intensity modulation as well as s
ome measures of their suppression are discussed.