Power Engineering. Соколова Е.В. - 24 стр.

       3. Under proper conditions the atom reverts to its earlier state and in doing so it
radiates energy. It is released by subjecting the molecules to electromagnetic waves
of the right frequency making the molecules emit their excessive energy. Conse-
quently the released energy is radiated as electromagnetic radiation to the stimulating
waves that are thus amplified.
       4. Light waves as well as radio waves, can be greatly amplified by beaming
them through masses of high energy atoms. Weak light or radio waves fed into the
maser are assumed by scientists to emerge amplified ones hundreds of times.
       5. In microwave devices such as klystrons and travel ling-wave tubes, moving
charged particles (electrons) interact with a microwave field; the internal energy is
directly transferred (converted) to microwave energy, and there is no flow of charge.
This internal energy, which is associated with the motion of electrons in atoms and
molecules, is quantized, that is the molecular energy can exist only in certain discrete
levels. Molecules in various energy states can interact with a microwave radiation
field of appropriate frequency. They may either absorb energy from the radiation
field and jump to a state of greater internal energy or else give up some of their inter-
nal energy and drop to a state of lower energy. The amount of internal energy thus
transferred (i. e. the difference in energy of the two energy levels) is linearly related
to the frequency of the radiation field.
       6. The elementary maser amplifier involves the use of two energy levels. The
molecular system is first disturbed and then put in an emissive condition with more
molecules in the upper of the two energy levels. A sophisticated method of exciting a
molecular system is the three-level maser, in which a strong microwave field equal-
izes the populations of two energy states and amplification is obtained at a lower fre-
quency by inducing between one of these two levels and an intermediate undisturbed
level. Both the two-level and the three-level masers require energy to be supplied to
the system at microwave frequencies.
       7. Masers are held to operate in the very highest known frequencies by the
electromagnetic spectrum. This means that energy waves emitted by masers move
faster than other signals and with lack of interference.
       8. Thus masers are characterized by two basic features. First they are inherently
low-noise devices, free of flicker noise, shot noise, and partition noise. Second, their
frequency, determined by the internal molecular structure, can be extremely high. Re-
cently, optical masers or "lasers" have been realized in the optical — frequency re-
gion. The great advance of masers is certain to come in the field of communications
especially in high quality space communications. The maser is reported to enable sci-
entists to measure the temperature of planets, and to do the first measurements of the
amount of hydrogen in a number of galaxies.
       9. In addition to amplifying radio and light waves, masers are capable of pro-
ducing signals that are one million or more times as sharp as conventional (ordinary)
signals. Masers are sure to have a promising future as they will be applied in numer-
ous fields. Our Russian scientists A. M. Prohorov and N. G. Basov are known to have
made great contributions to the maser development.



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