Leak Test with Laser Beam
There also are methods to check for leakages by means of laser beams. A test object is filled with a tracer gas to a certain overpressure. The outside of the test object is scanned with a CO2 Laser beam. If the Laser beam meets this gas escaping through a leakage, then the electrons of this gas are activated to a higher energy level by the laser beam, i.e. one or more electrons of the gas molecules are transported on a higher trajectory. When falling back on the original trajectory this energy is released again. This takes place by emission of photons (a light lightning with a certain frequency [colour]).
These lightning´s are detected by a suitable sensor and synchronized with the scanning raster. On a picture of the test object, shown on a monitor, the leak location can be recognized.