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Fireball generation from a high-intensity circuit breaker arc is interpreted here as a quantum-mechanical phenomenon caused by severe cooling of electrode material evaporating from contact surfaces. According to the proposed mechanism, quantum effects appear in the arc plasma when the radius of one magnetic flux quantum inside solid electrode material has shrunk to one London penetration length. A formula derived for the threshold discharge current preceding fireball generation is found compatible with data reported by Silberg. This formula predicts linear scaling of the threshold current with the circuit breaker’s electrode radius and concentration of conduction electrons.

The KLY hypersatellite spectrum of gaseous AI has been measured in photon excitation with a plane crystal Bragg spectrometer. The experimental energy of KCY; line is obtained. The result is in good agreement with available theoretical calculations. The K shell double photoionization cross-se.ction is estimated from the measured hypersatellite intensity and it is compared with existing theoretical calculations based on the shake theory and correlated wave functions. h

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