Intense source of @[email protected] (\(185\) and \(253.7\ \text{nm}\)) radiation produced by an electrical discharge in a @[email protected] with the inner side covered by an amalgam of mercury with another element such as indium or gallium to control the vapour pressure of the mercury. These @[email protected] have 2-3 times the UV output for the same @[email protected] as the standard @[email protected]