Using a hybrid-fluid model to simulate the ion-hose instability in long-pulse electron linacs

Abstract

A numerical model of the ion-hose instability for long-pulse electron linacs is presented, where the ion motion is represented by fluid parameters. In order to gain extra numerical stability, the fluid behavior of the ions is evolved via particle-in-cell (PIC) techniques. This methodology provides a much faster simulation than a full PIC calculation, allowing for end-to-end simulations of the ion-hose instability in actual linear accelerator configurations. After the description of the simulation model and some simple test cases, the instability is analyzed for a variety of nominal accelerator transport conditions. Simulations of the instability are provided for sections of the DARHT long-pulse accelerator that show different growth regimes of the instability. We find that large-amplitude growth is possible in accelerator and transport regions lacking uniform external focusing, for electron pulse lengths of 2 sec and longer.

Electron beam requirements for Smith-Purcell backward wave oscillator with external focusing

“…However, as discussed in Ref. [20], wiggler focusing provides better stability compared to PPM focusing. The second method assumes that the flat beam is generated inside the solenoid magnetic field by immersing a line cathode in the solenoid.…”

“…The first method assumes that a flat beam is generated in the field-free region, which is later focused using a wiggler field. Another way for focusing such a flat beam is to use periodic permanent magnet (PPM) focusing where one uses an axisymmetric periodic magnetic field as discussed by Carlsten et al [20]. However, as discussed in Ref.…”

Beam Imaging of a High-Brightness Elliptic Electron Gun

“…In addition, high-brightness elliptic charged-particle (electron, muon, proton, antiproton, and ion) beams have wide applications in other accelerators for nuclear physics research and high-energy density physics research because they are naturally matched to alternating-gradient focusing systems where the transverse section of the beam is a pulsating ellipse [7]. Furthermore, high-aspectratio elliptic beams will enable the research and development of advanced accelerators with planar structures [8,9]. This paper reports on the progress in an on-going experimental demonstration of a high-brightness spacecharge-dominated elliptic electron beam operating at 2290 V with a perveance of 1.0× 10 -6 .…”