There's also a German article with a short setup diagram at
http://www.ipp.mpg.de/ippcms/de/presse/pi/05_06_pi.html
and a short ~2MB video of the bang at
http://www.ipp.mpg.de/ippcms/de/presse/pi/05_06_kugelblitz.mpg
Pity that it is not a "contained" plasma ball, more like a plasma
"smoke ring". Interesting though that the plasma is greenish. Maybe
due to ionized natrium / chlorine from the salt water. Wonder if
other salts would result in other colours :-)
The German site's diagram shows a 5 kV DC supply and 500uF capacitor
bank, that's a few kJ, and more like can crusher than tesla coil.
cheers,
- Jan