Hydrogen Maser and iMaser Clock Technology

Maser stands for Microwave Amplification by Stimulated Emission of Radioation. The Hydrogen Maser is an active oscillator
with a natural output derived from the quantum transition between two of the hyperfine levels.(F=1, MF=0 to F=0, MF=0) of
the ground electronic state of atomic hydrogen.This corresponds to a well-known 21 cm line.

Molecular Hydrogen, supplied from a storage bottle dissociated into atoms by an HF plasma discharge in the H source. Leaving the H source, the atoms enter a State Selector which directs the beam of atoms in the appropriate quantum state (F=1, MF=0 and F=1, MF=1) into a quartz Storage bulb coated with Teflon to minimize the interactions of Hydrogen atoms with the bulb walls. The storage bulb is placed in the center of a Microwave cavity using the TE011 mode. The cavity is tuned and close to the hyperfine structure transition of the Hydrogen atom. The tuning of the cavity is controlled by the cavity temperature (coarse adjustment) and by a Varactor diode. A-coupling loop, mounted in the cavity, extracts part of the Maser energy to the low noise receiver and the Phase Lock Loop (PLL), which includes the local quartz oscillator (OCXO).


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