Electrical-spark tracking

Spark chambers (or "streamer chambers") are a set of 5 to 10 metal plates thin enough for high-energy particles to cross them, in a chamber filled with He or Ne when particles cross the plates, a trigger signal sets up a strong electric field, and sparks fly from plate to plate two photographic films mounted perpendicular to the plates and to each other record the spark tracks across the plates. The spark chamber has been superseded by drift chambers and silicon detectors. 

In polluted conditions where moisture and solid pollutants collect and in the condition of electrical stress which obtain in HV applications, small leakage currents flow across the surface of the outer insulator. The currents cause a rise in temperature which in turn causes dry bands to form on the surface of the insulator. Small sparks then cross the dry band the temperature of the sparks is 2000-3000 C, and the surface of the insulator can reach 450-600 C. Such temperatures can easily cause degradation of polymers with the development of carbonaceous tracking which extends in dendritic fashion. Alternatively, erosion can occur, causing cratering and final breakdown of the insulator. The worst damage is caused by currents of less than 20 mA. See Fig. 26.4. 

Increased friction and adhesion Sensitive electric instruments Meter sticking Cathode ray tubes Radiofrequency noise from sparks Printing Industry - paper tracking, "ink flying"... 

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