The X-Rays That Shouldn't Be There

For around 20 years, Caltech Professor of Applied Physics, Paul Bellan, and his group have been creating magnetically accelerated jets of plasma, an electrically conducting gas composed of ions and electrons, in a vacuum chamber big enough to hold a person. (Neon signs and lightning are everyday examples of plasma).

In that vacuum chamber, wisps of gas are ionized by several thousand volts. One hundred-thousand amps then flow through the plasma, producing strong magnetic fields that mold the plasma into a jet traveling around 10 miles per second. High-speed recordings show that the jet transitions through several distinct stages in a few tens of microseconds.

Bellan says the plasma jet looks like an umbrella growing in length. Once the length reaches one or two feet, the jet undergoes an instability that causes it to transform into a rapidly expanding corkscrew. This rapid expansion triggers a different, faster instability that creates ripples. [Caltech story]