A temperature of 2 to 3 billion degrees Kelvin -- hotter than the
interior of any known star -- has been achieved in a lab in New Mexico.
temperature record was set recently in a test shot at the Z Pinch
device at Sandia National Laboratory, where an immense amount of electrical
charge is stored in a device called a Marx generator. Many
capacitors in parallel are charged up and then suddenly switched
into a series configuration, generating a voltage of 8 million volts.
The process captured in a famous photograph, see
Physics News Graphics.
This colossal electrical discharge constitutes a current of 20
million amps passing through a cylindrical array of wires, which
implodes. The imploding material reaches the record high
temperature and also emits a large amount of X-ray energy
(see PNU 702).
Why the implosion
process should be so hot, and why it generates X-rays so efficiently
(10-15 percent of all electrical energy is turned into soft X-rays), has
been a mystery.
Now Malcolm Haines of Imperial College, in London, and his
colleagues, think they have an explanation. In the hot fireball
formed after the jolt of electricity passes through, they believe,
the powerful magnetic field sets in motion a myriad of tiny vortices
(through instabilities in the plasma), which in turn are damped out
by the viscosity of the plasma, which is made of ionized atoms.
In the space of
only a few nanoseconds, a great deal of magnetic energy is converted
into the thermal energy of the plasma. Last but not least, the hot
ions transfer much energy to the relatively cool electrons, energy
which is radiated away in the form of X-rays.
Haines et al.,
Physical Review Letters,
24 February 2006
Contact Malcolm Haines, firstname.lastname@example.org
Image at Physics News Graphics