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Published online: 4 March 2009 | doi:10.1038/nchina.2009.42

Plasma physics: Focus on your neutrons

Felix Cheung

Introduction

© (2009) APS

The neutron source — a device that emits neutrons — is useful in diverse applications in physics, materials and medicine. Because neutrons are freed in fusion reactions, a simple approach for generating them is to ionize a target — often deuterium — rapidly by an intense laser field. However, to obtain more neutrons, both the ion density and the ion temperature need to be maximized. Now, Hongbin Zhuo at the National University of Defense Technology in Changsha and co-workers¹ have proposed a simple idea that can lead to a high concentration of target ions at the appropriate temperature favourable for neutron production.

Their idea is to make the target into a thin-shelled, hollow sphere with a small opening, through which an intense laser pulse enters and fills the entire cavity. The trapped laser ionizes the inner shell surface, and the radiation pressure drives local electrons radially outwards, which creates a space–charge field that accelerates local ions towards the target.

When the ions become strongly heated, they create a thermal pressure that pushes them back to the cavity centre. The result is a peak of high ion density (pictured) and temperature at the cavity centre that is ideal for neutron production.

In a way, the target configuration resembles the cavity used in inertial confinement fusion experiments — except the former is much smaller and the mechanism of action is different. Based on their simulation, the researchers believe their design will help the realization of highly compact and localized neutron sources.

The authors of this work are from:
National Laboratory for Parallel and Distributed Processing, School of Computer Science, National University of Defense Technology, Changsha, China; Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, China; Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou, China; Institute for Theoretical Physics I, Ruhr University, Bochum, Germany; Department of Physics, Shanghai Jiao Tong University, Shanghai, China.

Reference

1. Zhuo, H. B. et al. Laser-driven inertial ion focusing. Phys. Rev. E 79, 015401 (2009).  | Article | ChemPort |