Devices
In the pioneering experiment, Los Alamos National Laboratory's FRX-L, a plasma is first created at low density by transformer coupling a large electrical current through a gas inside a quartz tube (generally a non-fuel gas for testing purposes). This heats the plasma to about 200 eV (~2.3 million degrees). An arrangement of external magnets keeps the fuel confined within the tube during this period. Plasmas are electrically conducting, allowing a current to be passed through them. This current, like any, will generate a magnetic field that interacts with the current. It is possible to arrange the plasma so that the fields and current will stabilize within the plasma once it is set up, self-confining the plasma. FRX-L uses the field-reversed configuration for this purpose. Since the temperature and confinement time is much lower than in MCF, by about 100 times, the confinement is relatively easy to arrange and does not need the complex and expensive superconducting magnets used in most modern MCF experiments.
FRX-L is used solely for plasma creation, testing and diagnostics. It uses four high-voltage (up to 100 kV) capacitor banks storing up to 1 MJ of energy to drive a 1.5 MA current in one-turn magnetic-field coils that surround a 10 cm diameter quartz tube. In its current form as a plasma generator, FRX-L has demonstrated densities between 2 and 4 × 10 cm, temperatures of 100 to 250 eV, magnetic fields of 2.5 T, and lifetimes of 10 to 15 µs. All of these are well within an order of magnitude of what would be needed for an energy-positive machine.
FRX-L was later upgraded to add an "injector" system. This is situated around the quartz tube, and consists of a conical arrangement of magnetic coils. When powered, the coils generate a field that is strong at one end of the tube and weaker at the other, pushing the plasma out the larger end. To complete the system, the FRX-L injector was to be placed above the focus of the existing Shiva Star "can crusher" at the Air Force Research Laboratory's Directed Energy Lab at the Kirtland Air Force Base in Albuquerque, NM.
At some point the plans were changed, and instead a new experiment, FRCHX, has been placed on Shiva Star. Similar to the FRX-L, it uses a generation area and injects the plasma bundle into the Shiva Star liner compression area. Shiva Star delivers about 1.5 MJ into the kinetic energy of the 1 mm thick aluminum liner, which collapses cylindrically at about 5 km/s. This collapses the plasma bundle to a density around 5x10 cm and raises the temperature to about 5 keV, producing neutron yields on the order of 10 neutrons "per shot" using a D-D fuel. The power released in the larger shots, in the range of MJ, needs a period of resetting the equipment on the order of a week. The huge electromagnetic pulse (EMP) caused by the equipment forms a challenging environment for diagnostics.
Read more about this topic: Magnetized Target Fusion
Famous quotes containing the word devices:
“So that with much ado I was corrupted, and made to learn the dirty devices of this world.
Which now I unlearn, and become, as it were, a little child again that I may enter into the Kingdom of God.”
—Thomas Traherne (1636–1674)
“There is nothing in machinery, there is nothing in embankments and railways and iron bridges and engineering devices to oblige them to be ugly. Ugliness is the measure of imperfection.”
—H.G. (Herbert George)
“The relationship between mother and professional has not been a partnership in which both work together on behalf of the child, in which the expert helps the mother achieve her own goals for her child. Instead, professionals often behave as if they alone are advocates for the child; as if they are the guardians of the child’s needs; as if the mother left to her own devices will surely damage the child and only the professional can rescue him.”
—Elaine Heffner (20th century)