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sibly because of these reasons the ion drive device has received the greater attention. However, ion accelerators designed for terrestrial 2 purposes are not particularly satisfactory for space application, ana considerable effort will be required to develop an ion accelerator suitable for space propulsion. Considerable effort is also required for the development of a suitable plasma accelerator. Nevertheless, plasma drive offers several distinct advantages over ion drive.

Because of the relative complexity of the interaction of magnetic fields and plasmas and the resulting variety of plasma accelerator configurations, experiments are needed to determine the design of suitable plasma drive devices. The Plasma Physics Department of Lockheeds Missiles and Space Division has been engaged for a considerable time in experiments involving plasma acceleration, and measurements are being made with several different plasma accelerators.

Description of the Apparatus. Fig. 1 presents a schematic of the collinear electrode plasma accelerator. In essence the device consists of a pair of collinear discharge electrodes connected to a

Insulated electrode lead to provide accelerating magnetic force


Electrode

Plasma discharge

Direction - of plasma acceleration

Electrode

To electrode energy storage system and high voltage povfer supply

Fig. I. Schematic diagram of the collinear electrode plasma accelerator.

low Inductance, high energy capacitor. The leads between the condenser and the electrodes are arranged to keep the inductance of the discharge circuit as low as possible and also to orient the direction of the discharge forces.

ion drive - ионный двигатель

* terrestrial - наземный

be engaged - заниматься (чем-л.)



2. APPLICATION OF DIGITAL COMPUTERS FOR AUTOMATIC TRANSLATION OF LANGUAGES

(Для перевода со словарем)

One of tfie tasks for wfiicfi a digital computer can be used is tlie automatic translation of languages. The idea of translation by computers was first suggested in 1946. The aim of the scheme is not, of course, to produce literary masterpieces, but to give rough-and-ready translations which are more or less correct in meaning and grammar. This is likely to be of tremendous value to scientists, who have a vast amount of foreign scientific literature available but are not able to read a great deal of it. Even very rough translations would be useful here, for they would allow the specialist to skim quickly through the papers and articles in his particular field of study and pick out those of special interest which could then be sent to human translators for more exact renderings.

The general idea, then, is to code the foreign words into numerical form and make the computer operate on these numbers in a certain routine to which the translation process can be reduced. Without going into particulars this routine involves three main operations - comparing the incoming foreign words with entries in a mechanized "dictionary," recognizing particular patterns of words (as in idioms), and transferring information to and from a store.

The size of a store necessary to contain the total vocabulary for a non-technical translation would be extremely large. The number of terms used in specialized branches of science, however, is considerably smaller than required for general literature. Consequently, by limiting the automatic translation to a particular branch of science, the "dictionary" may be reduced to a size manageable by present techniques of storage. Besides reducing the size of vocabulary, concentration on technical literature reduces the problem of ambiguity. And by further specialization on, say, a particular branch of mathematics, ambiguity of technical terms within that branch is lessened. For technical translation, then, a mechanized "dictionary" must be compiled in two stages: first, by collecting together the general language of mathematics, that is, the language common to all or most branches of mathematics - and, secondly, by assembling a glossary of all the technical words in the particular branches of mathematics. The translation of a paper on, say, group theory, would thus be preceded by feeding into a computer a "dictionary" of the general language of mathematics and a glossary of group-theory terms.

Automatic translation is, of course, a very specialized application of digital computers, but it is worth more than just a casual



mention because it does illustrate the i<ind of techniques which are iil<ely to be used more and more for non-numerical "data processing."

3. PLASMA MICROWAVE DEVICES

(Для перевода со словарем)

Promising applications of the properties of plasmas appear in the field of guidance and generation of high Rf energy. Since a column of plasma will support the propagation of various field configurations of electromagnetic waves, a considerable effort is presently being devoted to an understanding of plasma waveguides. The waveguide is the basic component of the microwave system, and its characteristics will determine and limit the other microwave devices which are possible. An electromagnetic wave travelling down a plasma column will have its phase and amplitude altered, depending on the plasma properties and configuration and prototype attenuators, and phase shifters have been built in several laboratories.

Plasma properties can also be used for waveguide switching. In addition, since plasma exhibits interesting properties such as the Faraday effect, polarization characteristics, double refraction and noniinearity, they can be utilized for circuit and microwave applications.

It has been demonstratecf that slow electromagnetic waves can )ropagate in a plasma cylinder in the presence of a dc magnetic ield. As a consequence, intense investigations are being made in attempts to utilize a plasma as, the slow-wave structure of travelling wave tubes. In this manner, the characteristics of the slow-wave structure can be altered externally by changing the plasma properties.

Suggestions have been put forth In which the nonlinear effects of a plasma at high power levels are utilized as the nonlinear propagating medium of a paramagnetic amplifier. The generation of millimeter waves by plasma techniques is another field of great interest and current importance.

In a gaseous discharge plasma system, it is possible for a metastable states of a given atom to be used as carriers of energy to excite specific quantum energy levels of another atom. If the excitation cross section for this process is large, then excess of atoms in this excited state will occur. This is precisely the condition required for maser action, and the successful operation of such a quantum plasma device producing maser osc llations at optical frequencies has been achieved recently.

Further schemes have been put forth whereby the ion sheaths surrounding hypersonic re-entry vehicles would be utilized as coherent radioactive elements and hence as a plasma antenna.



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