Impact of the Three-Wave Instability on the Spiral Line Induction Accelerator

摘要

The solenoidal and helical quadrupole magnetic fields that are used to transportthe high current beam in the spiral line induction accelerator may admit instabilities such as the electromagnetic three wave instability. Previous studies have shown that stability is easily maintained for energies up to approx. 40 MeV. Three wave growth rates for energies exceeding 40 MeV can be < or = .001/cm. Strategies are outlined for stabilizing or further reducing growth rates. These are (1) cyclotron detuning, where the instability is detuned by varying the axial magnetic field, (2) damping the instability through the use of discrete quadrupole focusing, which allows the instability to be detuned by varying the quadrupole wavenumber. The effectiveness of de-Qing and cyclotron detuning is discussed for the various instability regimes. Keywords: Q Factor, High current, Accelerator, Strong focusing. (JHD)