Characterization of Spark Discharges at High Pressure Conditions by Spectral Line Broadening

One of the most famous applications of spark discharges is the ignition of the petrol-air mixture in a cylinder of an Otto engine. In the system, an ignition coil generates a high voltage up to 45 kV that causes a spark between the electrodes of a spark plug. Spark plugs typically work in a pressure range of 10 to 30 bars close to the ignition point of a modern Otto engine. This ignition technology is wellengineered, but the plasma parameters, namely gas temperature and electron density of the spark plasma at high pressure conditions are unknown. For a conventional ignition system the electrode gap of the spark plug is 0.7 mm and the duration of this plasma is only a few hundreds of nanoseconds, which makes a challenge to infer consistent and reproducible results.