Beam Breakup in an Advanced Linear Induction Accelerator

Abstract

Two linear induction accelerators (LIAs) have been in operation for a number of years at the Los Alamos Dual Axis Radiographic Hydrodynamic Test (DARHT) facility. A new multipulse LIA is being developed. We have computationally investigated the beam breakup (BBU) instability in this advanced LIA. In particular, we have explored the consequences of the choice of beam injector energy and the grouping of LIA cells. We find that within the limited range of options presently under consideration for the LIA architecture, there is little adverse effect on the BBU growth. The computational tool that we used for this investigation was the beam dynamics code linear accelerator model for DARHT (LAMDA). To confirm that LAMDA was appropriate for this task, we first validated it through comparisons with the experimental BBU data acquired on the DARHT accelerators. Index Terms-Electron beam instabilities, linear induction accelerators (LIAs).

Beam breakup in a solid-state powered linear induction accelerator

“…Theory [5,6,7] predicts that, after a large number of cells (N), the maximum amplitude of the BBU asymptotes to I is the beam current in kA, tr Z is the transverse coupling impedance in Ohms/cm, B is the solenoidal guide field in kG, and indicates an average over the cells. This scaling of BBU growth has been experimentally validated [3,8,4,9], and is unmistakable in computer simulations based on models of beam interaction with the cavities [10].…”

The Ion-Hose Instability in a High-Current Multipulse Linear Induction Accelerator

“…Initial perturbations were ∼1% of the beam size at the LIA exit. In the linear regime (exponential growth), the resonant frequency is inversely proportional to beam radius as shown by (1). Since the matched beam radius varies significantly through the LIA (Fig.…”

“…Acceleration and transport by the 72 cells of the Scorpius LIA are illustrated in Fig. 1, which shows a solenoidal magnetic transport field designed to suppress the beam breakup (BBU) instability [1]. Although the ion-hose instability [2] is usually associated with long-pulse LIAs, it is also problematic for multipulse accelerators like Scorpius [3].…”

Direct measurement of the image displacement instability in a linear induction accelerator

“…Figure 3 shows that the results of the model (solid line) agree well with the measured data (dots). The second code [20,21], the Linear Accelerator Model for DARHT (LAMDA), has been benchmarked against theory, experimental data and other beam dynamics codes and was used to help understand what effect the BBU and resistive wall instabilities have on the IDI measurements.…”