The Z-Machine
The method of attaining a uniform plasma was reached in 1995 with the advancement of wire-array Z-pinches. This idea, like all the others, has also been around since the 1970's but, until now, could not deliver the power to implode large numbers of many small wires. This breakthrough is typified in the development of the Z-Machine, shown in the picture below. The Z-machine uses double-nested wires arranged so that the current vaporizes the outer array, and the induced magnetic field pushes the vaporized material inward. This geometry, it was found, reduces the instabilities in the implosion, and when the vaporized materials collide at the z-axis they create a shorter pulse of X-rays, producing temperatures of 1.8 million degrees[5].
Current Specifications of the Z-Machine:
[4]
Energy - 2.0 megajoules acheived
Power - 290 terawatts
Temperature - 155 eV (1.8 million Kelvin)
Output/Input Energy Ratio - 15%
Figure 3 - a time-elapsed photograph of the X-rays
produced by the Z-Machine
The
interior of the Z-Machine is depicted in the figure to the right.
The possibilities of a high-yield fusion reactor seem promising for Sandia National Labs. Though not achievable in its current state, the highly-hoped for successor to the Z-Machine, the X-1, is planned to provide 16 megajoules or radiation, ,allowing the main chamber to reach temperatures of 3 million Kelvin, their estimated temperature to start fusion[4]. However, the prospects of using such a machine to have a commercially viable source of energy may still be a long ways down the road.
Figure 4 - the components of the Z-Machine at Sandia Labs