The Ammonia Gas MSER is the first MASER to be developed in 1954. It is named so because it is based on the molecule of ammonia. It was developed by Towns, Gordan, & Zeiger.
Ammonia MASER is based on the fact that ammonia molecule consists of one nitrogen & three hydrogen atoms exist in two energy states, which differs in energy about 10^-4 eV.
This frequency lies in microwave region. Therefore ‘M’ also stands as microwave.
Thus the transition of molecule from higher to lowerenergy level will emit a photon of frequency 24000MHz.
The transition process may be set by an input signal of correct frequency or by spontaneous fall of one molecule which stimulates another and so on… till the process become self-sustaining.
To sustain the production of photon, more excited molecules are fed till the chamber become resonant cavity.
Construction & Working :
Let us learn the construction & working pointwise :
- It consists of an “O” shaped oven to excite the ammonia molecule. The excited molecule steam out through the outlet “H” and then pass through the seprater “S”. A seprator “S” consists of charged rod & is cylindrical in shape.
- Excited ammonia molecules are repeled by the electric field of charged rods of seprator while unexcited molecules are attracted, but since the force of repulsion from all the side of cylinder separator will balance, the excited molecule will continue to move along axis of seprator and reach the resonance cavity “R”. The unexcited molecule will be removed by attraction of electric field.
|Fig. Experimental setup
of Ammonia Gas MASER.
- In the resonance cavity the excited ammonia molecules are subjected to stimulated emission by allowing a beam of photon of frequency 24000MHz to enter the cavity through the wave guide “w” under the effect of incident microwave beam, the excited ammonia molecule give out photon of frequency 24000MHz by the process of stimulating emission.
- These photons further stimulates another photons & these stimulating photon come out through output signal as intense MASER beam.