A type of laser employing a very high discharge current, passing down a small bore to ionize a noble gas such as argon or krypton. The ionization process creates a population inversion for lasing to occur. A research laser useful for some industrial applications.

The process by which ions are formed.

Radiant power incident per unit area upon a surface, expressed in watts-per-centimeter-squared (W·cm^-2).  Symbol: E

Exposure to radiant energy, such as heat, X-rays, or light; the product of irradiance and time.