Broad band optical absorption spectroscopy investigations in a low-voltage circuit breaker using an ultra-bright source produced by a fast electric discharge

Summary form only given. In the low voltage range operation of a rail-gap circuit breaker, an electrical arc is created during the interruption of a multi-kilo ampere short circuit current. Then the arc is displaced from its ignition area to a quenching area. Previous studies have been performed to understand the physical phenomena observed during the circuit breaker operation. These studies, using optical emission spectroscopy in the experimental part, demonstrated that the hot gas surrounding the arc plays an important role in the arc re-strike phenomena. To investigate this hot gas mainly composed of species ablated from the wall, optical absorption spectroscopy is well adapted because of the very weak spectral emission. Due to the single shot operating mode of the circuit breaker, a broad spectral band source is more suitable than a tunable laser especially in the case of molecular band absorption. In this connection, a fast, powerful electric discharge device has been developed. The strong magnetic compression due to the fast rise of the discharge current leads to a hot and dense plasma at the time of maximal compression. At this moment and in our operating conditions, the plasma radiation is very similar to a blackbody at a temperature well above 30000 K. This plasma source turns out to be very convenient for the broad band absorption spectroscopy due to its brightness, stronger than the circuit-breaker arc one, and its short duration providing excellent time resolved measurements. This source and the absorption spectrum by hot gas in circuit breaker will be presented during the conference.