Z hot

US Department of Energy's research facility 

's Z machine has produced plasma that exceeds temperatures of 2 billion degrees Kelvin, which is hotter than the interiors of stars.

The unexpectedly hot output, if its cause were understood and harnessed, could eventually mean that future nuclear fusion plants could be smaller and less costly yet produce the same amount of energy as larger plants.

The phenomenon may also explain how astrophysical entities like solar flares maintain their extreme temperatures.

The Z machine generates the highest power X-rays in the world to create extremely high temperatures in hydrogen fusion fuel. It accumulates energy then targets it in a pulse lasting milliseconds onto an array of thin metal wires. The wires explode, creating plasma. The intense magnetic field created by the current compresses, or "pinches," the plasma, generating X-rays.

The very high radiation output also creates new experimental environments to help validate computer codes responsible for maintaining a reliable nuclear weapons stockpile safely and securely - the principle mission of the Z facility.

The new achievement was obtained in part by substituting steel wires in cylindrical arrays 55 mm to 80 mm in diameter for the more typical tungsten wire arrays, approximately only 20 mm in diameter. The higher velocities achieved over these longer distances were part of the reason for the higher temperatures.

Sandia scientists previously assumed high temperatures to be produced entirely by the kinetic flight and intersection of ions and electrons, unaided by accompanying microturbulent fields.