A distributed radiator, heavy ion target driven by Gaussian beams in a multibeam illumination geometry

Abstract

An inertial confinement fusion target driven by ion beams in a multibeam illumination geometry is presented. Two dimensional integrated LASNEX calculations (ion beam deposition to fusion burn in one computer simulation) predict a gain of greater than 65 for this target. Each beam has a Gaussian density profile and is focused to an elliptically shaped spot. Multiple beam ellipses are overlayed to form an annulus on the end of the cylindrical hohlraum. The beams enter at angles relative to the cylindrical axis of the hohlraum that are consistent with both liquid wall chamber protection and the space required for a final focusing system upstream. For an accelerator that is 25% efficient (η = 0.25), a gain G of 65 leads to ηG greater than 16; a reactor with a reasonably small recirculating power fraction requires ηG greater than 8-10.

Overview of Theory and Modeling in the Heavy Ion Fusion Virtual National Laboratory

“…At this time, electrons from the plasma layers and from the beam-pipe walls provide the largest share of beam neutralization, although neutralization by photoionization electrons becomes dominant as the beam reaches the target. An important finding of this and similar simulations is that the beam waist for either type of pulse is close to values required by current distributed-radiator targets [56]. The IPROP code treats the beam ions kinetically; however, the plasma is described with a two-fluid model.…”

Drift compression and final focus systems for heavy ion inertial fusion

“…In addition, we need to be able to shape the driver beam energy as a function of time in order to optimize compression. In contemporary target designs based on heavy ion inertial fusion, a beam pulse consisting of a prepulse of 1.5 MJ and a main pulse of 4.4 MJ is envisioned [20]. Obtaining the optimal pulse shape for an ion beam or laser pulse will prove to be a difficult task and puts additional requirements on the accelerator or laser system.…”

“…The prepulse and the main pulse can be accelerated in the same accelerator up to an energy of 3 GeV [20].…”

“…The average beam current in the 4.4 MJ main pulse of 4 GeV delivered in 10 ns will be about 3.4 kA when using 32 beams [20].…”

Results on intense beam focusing and neutralization from the neutralized beam experiment

“…These beams are focused and directed such that they intersect before striking the target and then strike the target as they are expanding into an annular configuration [24]. The target chamber is filled at low pressure with a gas such as flibe.…”