Induction Linac Systems Experiments Research Articles

Design and construction of a large aperture quadrupole electromagnet

We are currently constructing a prototype quadrupole electromagnet for the proposed Induction Linac Systems Experiments (ILSE) at LBNL. ILSE (PUB-5219, 1989 (Lawrence Berkeley Laboratory)) will address many physics and engineering issues relevant to the design of a heavy ion fusion driver accelerator. The pulsed electromagnet has two layers of current windings and will produce a field gradient of 28 T m −1, with a usable aperture radius of 6 cm. It operates at a repetition rate of I Hz, steady state. In this paper, we discuss how the interaction of various concerns such as maximum dynamic aperture, short lattice period, field quality, iron yoke weight, heat transfer, and voltage stand-off have led to our particular design choices. We also present two- and three-dimensional numerical calculations concerning field topography and the results of transport simulations of space-charge-dominated ion beams with ILSE parameters.

ILSE Heavy Ion Accelerator

Lawrence Berkeley Laboratory (LBL) and Lawrence Livermore National Laboratory (LLNL) propose to build at LBL the Induction Linac Systems Experiments (ILSE), the next logical step towards the eventual goal of a heavy-ion induction accelerator powerful enough to implode or {open_quotes}drive{close_quotes} inertial-confinement fusion targets. ILSE is a 10 MeV heavy ion accelerator system that will establish the beam dynamics understanding required for a heavy ion IFE driver. Space charge dominated beams with driver scale dimensions will be employed. ILSE, although much smaller than a driver, will be the first experiment at full driver scale in several important parameters. Most notable among these are line charge density and beam cross section. Nearly all accelerator components and beam manipulations needed for an inertial fusion energy (IFE) driver will be tested. The ILSE accelerator and research program will permit experimental study of those beam manipulations required of an induction linac inertial fusion driver that have not been tested sufficiently in previous experiments. ILSE is also an important step in driver technology development for heavy ion drivers.

The ILSE experimental program

The Heavy-Ion Fusion Accelerator Research Program at Lawrence Berkeley Laboratory has proposed building a 10 MeV induction linac systems experiment, ILSE, to investigate accelerator physics and beam manipulations which are needed or desirable for an induction linac driver. This paper describes the experiments proposed for ILSE: transverse beam combining, drift compression, bending of space-charge-dominated beams, final focus, recirculation, and some studies of beam propagation in the environment of the reactor chamber.

Three-dimensional particle simulation of heavy-ion fusion beams*

The beams in a heavy-ion-beam-driven inertial fusion (HIF) accelerator are collisionless, nonneutral plasmas, confined by applied magnetic and electric fields. These space-charge-dominated beams must be focused onto small (few mm) spots at the fusion target, and so preservation of a small emittance is crucial. The nonlinear beam self-fields can lead to emittance growth, and so a self-consistent field description is needed. To this end, a multidimensional particle simulation code, warp [Friedman et al., Part. Accel. 37-38, 131 (1992)], has been developed and is being used to study the transport of HIF beams. The code’s three-dimensional (3-D) package combines features of an accelerator code and a particle-in-cell plasma simulation. Novel techniques allow it to follow beams through many accelerator elements over long distances and around bends. This paper first outlines the algorithms employed in warp. A number of applications and corresponding results are then presented. These applications include studies of: beam drift-compression in a misaligned lattice of quadrupole focusing magnets; beam equilibria, and the approach to equilibrium; and the MBE-4 experiment [AIP Conference Proceedings 152 (AIP, New York, 1986), p. 145] recently concluded at Lawrence Berkeley Laboratory (LBL). Finally, 3-D simulations of bent-beam dynamics relevant to the planned Induction Linac Systems Experiments (ILSE) [Fessenden, Nucl. Instrum. Methods Plasma Res. A 278, 13 (1989)] at LBL are described. Axially cold beams are observed to exhibit little or no root-mean-square emittance growth at midpulse in transiting a (sharp) bend. Axially hot beams, in contrast, do exhibit some emittance growth.

ILSE: The next step in heavy ion fusion research

Induction Linac Systems Experiments is the next experiment planned by the Heavy Ion Fusion Accelerator Research (HIFAR) group at LBL, following the recent completion of the MBE-4 experiment. ILSE at 10 MeV will address many of the key physics and technology issues of HIF such as performance of a multiple beam, high voltage injector, high intensity electrostatically-focused transport, beam combining, high intensity magnetically-focused transport, drift-compression and energy-tilt removal, high intensity transport around a magnetic bend, and, possibly, recirculation. Presuming a “new start” in FY 94, experiments could begin with ILSE in FY 97.