17. Plasma generator

As is well known, electric current can be generated if a metal conductor continually crosses the lines of force of a magnetic field. This is the principal feature of all de­signs of modern electric generators and electrical en­gines^

However, a generator can be constructed with nothing moving inside, thus eliminating the need for a steam turbine. A copper wire acts as a conductor in ordinary dynamos. How­ever, the metal could be successfully replaced by a jet of gas heated to a plasma state. Plasma is a rather new term in science and engineering. This term denoted another state of matter — the fourth state besides the solid, liquid and gaseous. It is caused by heating the matter to a temperature of 4000-5000°C and higher. In this case the so-called ionized gas is produced with a tremendous mass of free electrons forced away from the atoms. In this state a substance becomes an excellent conductor of current.

If a jet of plasma is directed between the poles of a power­ful magnet, an electric current would result which could be carried elsewhere by special electrodes. Thus, the rotor with the conductors, unlike the dynamo, is replaced here by a gaseous conductor continually crossing the magnetic field.

The efficiency of transforming the energy of fuel heat into electric current in a plasma generator can be brought to 55-56 per cent, and even to 70 per cent some day.

Though there are many difficulties in developing a plas­ma generator or, in other words, magnetohydrodynamic genera­tor, Soviet scientists and engineers believe that It is a practical task. To fulfil this task it is necessary to study the physical properties of the plasma and to find the means of increasing its density and temperature.

Scientists and engineers are concentrating their atten­tion on developing a power-generating installation based on the magnetohydrodynamic principle.

18. Laser

A decade or so ago a new principle of electromagnetic wave generation, was discovered almost at one and the same time in the Soviet Union and America. Light and radio waves are known to be electromagnetic oscillations. A few years ago the new principle was applied to generate visible radio waves, i. e. light. The device used is called laser, or opti­cal maser.

Under ordinary conditions all bodies absorb electromag­netic oscillation, either radio or light waves. Now scientists have developed a method of electromagnetic waves passing through substances, so that the waves are not absorbed but amplified many times. A laser beam is generated neither by an incandescent filament nor by an electric arc. It is pro­duced in a ruby crystal. A laser beam is a thousand million times brighter than sunlight.

Laser beams possess some remarkable qualities. One of them is negligible divergence, unlike that of a searchlight beam. When a laser was directed towards the moon, it lit up an area only a few miles in diameter.

A second quality is that the waves of a laser beam have a highly uniform frequency and their stability is much great­er than the oscillations emitted by an ordinary radio trans­mitter. Finally a system of lenses enables a laser beam to be focused to a point at which all its energy is concent­rated.

Laser beams can be used for precision machining of the hardest materials such as diamonds, hard alloys, etc.

It has recently been theoretically proved that a laser beam can be turned into electricity with high efficiency.

Scientists have developed different types of lasers and among the latest are lasers with semiconductor sources of light. Perhaps the most interesting thing about semiconduc­tor lasers is that they can transform electrical energy directly into light wave energy. They perform it with an efficiency of one hundred per cent as compared with a maximum of about one per cent of other lasers.

Theoretical calculations have shown that devices similar to semiconductor lasers can also transform the energy of light radio waves into electrical energy with an efficiency of up to 100 per cent. This means that electric power may be trans­mitted over considerable distances with negligible loss without any use of transmission lines.

Today laser beams are used to machine diamonds, cut and weld the hardest alloys and cure people. They find applica­tion in scientific research, computer techniques, communica­tions and in monitoring cosmic bodies.

Laser design is still far from being perfect but remarkable results have already been obtained both in this country and abroad.

In time lasers will have the most different applications. They can be used to control chemical reactions, to produce high temperature plasma, to raise the sensitivity of radio

telescopes, thus enabling them to be used to study galaxies inaccessible to modern instruments; to treat diseases and accelerate elementary particles.