Linear Induction Accelerator with Magnetic Steering for Inertial Fusion Target Injection

A traveling-wave induction accelerator was designed and built to launch 1 cm diameter cylindrical aluminum tubes (surrogate IFE targets) into a vacuum chamber at speeds greater than 50 m/s.

The accelerator is 0.55 m long with 300 coils. Each coil is energized 30 degrees out of phase with the adjacent coils resulting in a traveling sinusoidal magnetic field that moves past the projectile with resulting accelerating force.

Saddle coils surrounding the axial drive coils provide projectile spin.

Four saddle coils were placed around the projectile’s flight path at a distance of 0.4 m from the barrel. AC voltage energizes these coils resulting in an AC quadrupole magnetic field that provides a centering force as the projectiles pass through the coils.

To further improve accuracy, an actively controlled, in-flight, magnetic steering system was placed after the initial passive steering coils. This system measured the position of the projectile at two locations, in real time and adjusted the AC current in another set of four saddle coils to correct the measured trajectory errors. The first set of steering coils improved the standard deviation by a factor of 8 and the second set by an additional factor of 3, for a total factor of 24 improvement.