14 DAY TRIAL // Scientists working with the Z machine, the largest X-ray generator in the world, are puzzled by their own achievement: a temperature around 130 times higher than the temperature inside the Sun.
"At first, we were disbelieving," said project leader Chris Deeney. "We repeated the experiment many times to make sure we had a true result."
Previous experiments also managed to obtain staggering temperatures such as 500 million degrees Celsius, but 2 billion degrees isn't something they had expected. A thermonuclear explosion (an H-bomb) produces temperatures estimated to reach "only" tens of millions degrees.
Such colossal temperatures are measured by optical means - in a similar way as there exists a connection between temperature and the height of a liquid in a tube (which allows us to measure temperature with a thermometer), there exists a connection between the temperature of plasma and the wavelength of the emitted light (which allows measuring such huge temperatures).
The Z machine, which is housed at Sandia National Laboratories, works by discharging around 20 million amperes through a vertical array of very fine tungsten wires. The wires are vaporized into a cloud of ionized gas, i.e. plasma. Due to the fact that the plasma particles are electrically charged they can be maneuvered with the help of a magnetic field. The magnetic field here is used to squeeze the plasma into a vertical shape of the thickness of a pencil lead.
The collapsing plasma generates huge bursts of energy, especially in the form of X-rays. To get a certain sense of proportion: The power of these bursts, which last for around a trillionth of a second, is 80 times larger than the entire world's electrical power usage. In 2003 the lab announced that it also detected neutrons - a sign that fusion had taken place, i.e. that they had replicated the process that takes place inside the Sun or in an H-Bomb. (Not surprisingly, the Z machine is also used to simulate nuclear weapons.)
The Sandia researchers have now changed the wires with slightly thicker steel wires, which allow the plasma ions to travel faster and thus achieve higher temperatures. However, they weren't expecting the new record. Yet another thing that puzzles the scientists is that the high temperature was achieved after the plasma's ions should have been losing energy and cooling.
Sandia consultant Malcolm Haines speculates that they might have stumbled upon some unknown source of energy, because when the high temperature was achieved, the Z machine kept releasing more energy than was originally put in. Such a thing usually happens only when nuclear reactions occur and provide the extra jolt of energy just as the plasma ions are beginning to slow down.