Fusion reactors heat a plasma of the hydrogen isotopes deuterium and tritium under immense pressure until their nuclei overcome the natural force of repulsion and fuse together. Upon fusing they form helium nuclei, releasing excess neutrons and huge amounts of energy.
Fusion reactions are the power source of the stars, and would be the most powerful source of clean energy on the planet. Currently there are two multibillion dollar facilities attempting to achieve stable fusion reactions; the ITER fusion reactor in France, and the National Ignition Facility (NIF) in California.
ITER will be ready to test its fusion reactor in about 2019 or 2020, and will trigger the reaction by containing the plasma fuel in powerful magnetic fields, and then heating it with particle beams and radio waves.
NIF has already started testing its design, whereby it uses a very powerful laser pulse to crush a tiny capsule filled with plasma. Unfortunately it has not yet achieved any significant levels of energy production.
It actually turns out that the group closest to achieving nuclear fusion has done so on a far smaller budget than ITER or NIF.
Researchers at the Sandia National Laboratory in Albuquerque, New Mexico, are on track to test their reactor before the end of 2013, and have high hopes that it will reach break-even. Break-even is the point at which the process produces as much energy as was consumed to trigger the reaction, and is a huge step along the path to achieving full nuclear fusion reactions that can power the planet in the future.
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Sandia use a method similar to NIF, however they use their MagLIF technology to instantly crush the fuel, a process known as inertial confinement fusion, with a magnetic pulse, not a laser pulse.
The process involves placing a tiny cylinder, about 7mm in diameter, filled with the deuterium and tritium plasma, inside their Z machine. The Z machine is an electrical pulse generator, capable of delivering 26 million amps in a short pulse lasting just milliseconds. As the vast current passes along the walls of the cylinder it creates a magnetic field that exerts a huge force on the walls, instantly crushing the cylinder and compressing the fuel inside.
After initial tests the scientists discovered that the Z machine was not powerful enough to produce sufficient heat to trigger a break even reaction. Researcher Steve Slutz led a team to investigate how they might enhance the process, and with the help of various computer simulations they discovered three changes that they could make to increase the heat of the reaction.
- They would apply the pulse of current in an even shorter period of time, just 100 nanoseconds, in order to increase the speed of the implosion.
- They would preheat the fuel inside the cylinder with a laser pulse just before their Z machine delivered its pulse, so that the starting temperature of the reaction is much higher.
- They would place the cylinder in a magnetic containment field to prevent any heat from escaping in the form of charged particles.
Sandia’s plasma physicist, Ryan McBride, is heading the team that are making the upgrades and checking to see if the computer simulations were accurate.
The first change, delivering the pulse in a shorter time, has been made, and McBride was proud to announce that “it performed as predicted.” The other two changes will be made in the coming year, and they hope to put all three modifications together by the end of 2013 for another attempt at break-even.
By. James Burgess of Oilprice.com