Effects of a solenoidal focusing field on the electron-ion two-stream instability in high-intensity ion beams

A rigid-beam model is used to investigate the influence of a solenoidal foc using field B-0(e) over cap (Z) on the electron-ion two-stream instability that can occur in high-intensity ion beams when an (unwanted) component of background electrons is present. A relatively weak solenoidal magnetic fiel d strongly constrains the transverse electron motion and can lead to a sign ificant reduction in instability growth rate whenever omega (2)(pe) much gr eater than 2(n(b)e(b)/n(e)e)omega (2)(pe). Here, omega (ce) = eB(0)/m(e)c i s the electron gyrofrequency, omega (pe) = (4 pin(e)e(2)/m(e))(1/2) is the electron plasma frequency, and n(b) and n(e) are the ion and electron numbe r densities. (C) 2001 Elsevier Science B.V. All. rights reserved.