High-Yield Z-Pinch Thermonuclear Neutron Source

Introduction: Neutron beams are useful for many applications, from noninvasive imaging and characterization of materials to producing medical isotopes and detecting hidden explosive devices. Some applications require high-energy neutrons created in fusion nuclear reactions between deuterium (D) and tritium (T). To achieve thermal fusion, deuterium or DT plasma must be heated to about 10 8 K, which is a challenging task. One of the pathways to controlled thermonuclear fusion is inertial confinement fusion (ICF). High-energy ICF lasers, such as OMEGA at the University of Rochester and the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, as well as ICF pulse power facilities, such as the Z accelerator at Sandia National Laboratories, compress and heat deuterium or DT-filled capsules by strong laser or X-ray radiation. The highest thermonuclear DD neutron yield of the pre-NIF era is about 3 × 10 11 , obtained by direct capsule illumination with laser beams on OMEGA and by X-ray compression on Z. In the future, NIF will deliver ~180 kJ of X-ray energy to the capsule. DT neutron yield corresponding to " breakeven " (the same energy input as released in a DT reaction) is 6 × 10 16. Neutron yields above 6 × 10 16 can only be produced when the fusion energy release exceeds the input, indicating ignition and fusion energy gain. On the other hand, a DD plasma at the same temperature and density would produce a fusion neutron yield about two orders of magnitude less due to lower reaction cross section, that is, about 6 × 10 14. Deuterium fusion neutron yields of this magnitude could only be expected from ignition-scale ICF facilities, only one of which, NIF, has been built so far. 13 , exceeding the previous ICF record by two orders of magnitude, has recently been obtained on Z without a capsule implosion. A deuterium gas column was imploded in cylindrical geometry by a 15 MA, 100-ns-long current pulse, as illustrated by Figs. 1(a) and (b). The most powerful, fast, multi-MA current driver in the world, shown in Fig. 1(c), is much smaller and simpler to operate than ignition-class lasers. Non-thermonuclear DD fusion neutrons have been produced in Z-pinch plasmas at pinch currents up to about 2 MA for many years. They were generated by relatively small quantities of " beam " deuterium ions accelerated in the strong electric fields accompanying the development of instabilities in the pinch. …