Posted on: 14th November 2011

29th October, 2011: The staff at Culham downed their tools and focussed on a different type of plasma for an evening to celebrate fireworks season in the UK. Several hundred staff and their families congregated at Culham for a impressively-sized bonfire and professional firework display.

Swiss physicist Patrick Blanchard from the EFDA JET department was there with his wife and two children. “It was a good time with the family, the kids were happy” he said. But how did he compare the quality of the plasma with JET? “It was a good plasma; short-lived… but perhaps more accessible [than JET] for the younger generation!”

A JET plasma: the hottest part is transparent.

A JET plasma: the hottest part is transparent.

The show itself was fired by 3 crew from Kimbolton fireworks, who let off over 150 fireworks during the show. “But each one of those might contain up to 660 separate explosive tubes” explained display director Simon Page. However, fireworks temperatures are a far cry from a JET plasma: gunpowder burns at about 1,500 degrees Celsius, the bright sparkles from magnesium are at about 2,200 degrees Celsius and the flash powders to generate the loud bangs and flashes are at nearly 3,000 degrees Celsius – nothing compared to the hundreds of millions of degrees in the middle of the JET plasma.

Surprisingly the extreme heat of a JET plasma would make for poor fireworks. Light is emitted by electrons changing orbits around their nuclei, so the central, hottest part of the plasma is transparent because the gas is completely ionised. Only where the plasma is degraded at the cooler edges is visible radiation given out. And the elements in the fireworks that create the beautiful colours – barium for green, copper for blue and strontium for red – would be considered impurities in JET.

Another contrast is that, viewed from the control room the JET plasma is silent. “This might have been better for my daughter, Emma (aged 4)” laughs Patrick. “She was scared of the loud bangs!”