Before revision: A hydrogen radio frequency discharge, the first element inside a hydrogen maser (see description below) A maser (; acronym of microwave amplification by stimulated emission of radiation) is a device that produces coherent electromagnetic waves ( originally,
After revision: A hydrogen radio frequency discharge, the first element inside a hydrogen maser (see description below) A maser (; acronym of microwave amplification by stimulated emission of radiation) is a device that produces coherent electromagnetic waves ( i.e.