Sceptre (fusion reactor)
Sceptre was a series of early fusion power devices based on the Z-pinch concept of plasma confinement, built in the UK starting in 1956.
They were the ultimate versions of a series of devices tracing their history to the original pinch machines, built at Imperial College London by Cousins and Ware in 1947.
When the UK's fusion work was classified in 1950, Ware's team was moved to the Associated Electrical Industries (AEI) labs at Aldermaston.
When George Paget Thomson failed to gain funding from John Cockcroft's Atomic Energy Research Establishment (AERE), he turned over the project to two students, Stanley (Stan) W. Cousins and Alan Alfred Ware (1924-2010[1]).
He met fellow fusion-fascinated Peter Thonemann, and the two developed a similar small machine of their own at Oxford University's Clarendon Laboratory.
When the outer portions hit the walls of the container, a small amount of the material would spall off into the plasma, cooling it and ruining the reaction.
This field would, due to Lenz's law, opposed the motion of the plasma toward it, hopefully slowing or stopping its approach to the sides of the container.
[2] Convinced that the metal tube was the way ahead, the team then started a long series of experiments with different materials and construction techniques to solve the arcing problem.
[8] To better characterize the problem, the team started construction of a larger aluminum torus with a 12-inch bore and 45 inch diameter, and inserted two straight sections to stretch it into a racetrack shape.
[6] A camera placed at the focal point was able to image the entire plasma column, greatly improving their understanding of the instability process.
Electrical arcing and shorting between the tube segments became a problem, but the team had already learned that "dry firing" the apparatus hundreds of times would reduce this effect.
Photographs through a slit in the side showed the plasma column remaining stable for 300 to 400 microseconds, a dramatic improvement on previous efforts.
Working backward, the team calculated that the plasma had an electrical resistivity around 100 times that of copper, and was able to carry 200 kA of current for 500 microseconds in total.
