Compact active atomic hydrogen maser in Beijing Institute of Radio Metrology & measurement

In this paper, a compact active hydrogen maser in the Beijing Institute of Radio Metrology and Measurement is described. It uses the active mode of operation, cavity which is dielectrically loaded by the sapphire. The cavity is 18 cm outside diameter and 20 cm high, and weighs only 2.5 kg. Based on the sapphire-loaded cavity design, the volume of the total hydrogen maser has been reduced remarkably. The most recent stability data from the compact hydrogen masers is presented, which was measured by National Institutive of Metrology (3×10^-13@1s, 3×10^-15@1day). The compact hydrogen maser can be used for portable or space born application.