Sceptre IV¿a megajoule discharge system

Equipment for the production of a ring discharge of the Zeta or Sceptre type is described. The principles of design for the equipment, which uses 1 MJ of stored energy, are outlined, and details of the components are given. The discharge tube is made of accurately machined copper sectors forming a torus 2m in diameter and 30cm in bore. The stabilising magnetic field of up to 0.5 Wb/m2 is produced inside the torus by solenoidal coils supplied from a pulsed rectifier set of peak output 10.5kA at 110V d.c. The stored energy from the capacitor bank is discharged into the primary of the transformer, in which the ring discharge acts as the secondary. This primary current is switched by a specially developed ignitron circuit, which provides also a clamping connection to increase the current, while preventing reverse voltage on the capacitor bank. The performance of the apparatus is described as a result of three years´ operational experience. The peak gas-discharge current recorded is about 720kA, and a discharge resistance of about 0.001¿ is estimated. Experimental results relating to the design are discussed.