Space-charge limitation in a high-current betatron due to the negative-mass effect

Experiments demonstrate a longitudinal instability of the negative-mass type in a high-current betatron at the time electrons are injected into the accelerating chamber. This instability limits the charge which can be captured in the acceleration mode; hence, in the design of high-current betatrons, the charge which can be accelerated must be consistent with the threshold number of particles for the onset of this instability for a given injected-electron energy and magnetic field index. (AIP)