ISSN:0034-6748    

DOI:10.1063/1.1752059

出版商:AIP    

年代:1936

数据来源: AIP

摘要:

The useful sensitivitySof a tube counter exposed to feeble gamma‐radiation is proportional to (N−B)/(N+B)½, whereBis the background counting rate andNis the counting rate when the gamma‐ray source is present.Sdepends upon the product of (a) the efficiency of production of secondary electrons in the counter by the incident radiation, and (b) the efficiency of the tube counter in discharging once for each such secondary electron formed within its sensitive volume. Systematic comparison of many forms of tube counters reveals that the sensitivity to gamma‐radiation from a source of given strength and geometry, may be markedly increased (a) by increasing the effective area of the cathode by employing screen‐wire cathodes or grooved tube cathodes in place of solid smooth cathodes, and by using cathodes of high atomic number. If the cathode is not radioactive, various cleaning treatments do not increase its sensitivity. Temperature changes between 0° and 45°C do not appreciably affect the copper cathode tube counter. The sensitivitySmay be increased further (b) by careful selection of the operating voltage and the pressure of the filling gas. For every counter an optimum pressure and voltage may be found at which the counter is many times more sensitive than it would be if no care were given to the selection of these operating conditions. For a tube counter 12 cm long and 2 cm in diameter maximum sensitivity is obtained with a 100‐mesh copper gauze cathode when the counter contains air at 6.5 cm Hg pressure and is operated 170 volts above threshold. The elevated sensitivity of these gamma‐ray counters permits the direct measurement of the feeble gamma‐radiation from the radioactive impurities in ordinary granitic rocks, and, when combined with independent measurements of the uranium content by the radon emanation method, leads to thorium measurements having a probable statistical error of about 12×10−7g Th per g rock when only two hours of measurements are made on 1400 g of rock.

ISSN:0034-6748    

DOI:10.1063/1.1752060

出版商:AIP    

年代:1936

数据来源: AIP

摘要:

Randomly distributed pulses, of any voltage shape, and of varying magnitude, actuate an amplifier whose output meter indicates only the average rate of arrival of the pulses. Counting rates of 30 per minute up to several thousand per minute are read directly from a rugged meter. The apparatus is a.c. operated, is portable, and is particularly adapted to the study of feeble gamma‐radiation. The apparatus consists essentially of a preamplifier, a uniform pulse generator based on a relaxation oscillator or on an inverter circuit, an output amplifier stage, and a capacity‐resistance electrical tank circuit for performing the averaging process.

ISSN:0034-6748    

DOI:10.1063/1.1752061

出版商:AIP    

年代:1936

数据来源: AIP

摘要:

The counting rate meter, or vacuum tube speedometer, is an integrating and averaging instrument with an electrical, exponentially decaying memory. It is designed to replace message‐register equipment in all particle counting apparatus, and is ideally suited to continuous photographic recording. The average current to the output meter is proportional to the counting rate for constant sources or for decaying sources whose mean life is significantly greater than the time constantRCof the output tank circuit. ThisRCis analogous to a radioactive mean life and may be regarded as the mean memory time. While the output current depends only on the output resistanceR,and not on the output capacitanceC(except for very rapidly decaying sources), the statistical fluctuations in the output current depend uponRC,and are equivalent to the fluctuation expected in a time interval of 2RC.Expressions are derived for the condenser chargeQ,or output currentQ/RC,for constant and decaying sources of radiation, as well as for the expectedfractionalstatistical fluctuations in these cases.

ISSN:0034-6748    

DOI:10.1063/1.1752062

出版商:AIP    

年代:1936

数据来源: AIP

摘要:

A receiver for use in radiometeorography is described. It is one which has given satisfactory performance in this field for about one year. It is based on the Jones 5‐meter superheterodyne receiver. Designed for the reception of pulse‐type signals it has a low response to random noises.

ISSN:0034-6748    

DOI:10.1063/1.1752063

出版商:AIP    

年代:1936

数据来源: AIP

摘要:

A compact apparatus for making Laue, rotation, and Schiebold‐Sauter photograms, without the intermediate transfer of the crystal, has been constructed. Back reflection photograms may also be made. An accurate horizontal scale and verniers, combined with a microscope which may be used as an autocollimating telescope, facilitates the adjustment of the crystal, and permits interfacial angle measurements. All essential parts are readily adjustable with respect to the goniometer axis.

ISSN:0034-6748    

DOI:10.1063/1.1752064

出版商:AIP    

年代:1936

数据来源: AIP

摘要:

A simple amplifier and recorder circuit for discriminating between partial and total coincidences of Geiger‐Mu¨ller counters is described.

ISSN:0034-6748    

DOI:10.1063/1.1752065

出版商:AIP    

年代:1936

数据来源: AIP

摘要:

Two new forms of Wilson cloud apparatus, developed for stratosphere balloon flights and suitable for portable use, are described. The machines are of light weight, require only small amounts of electric power, and are arranged for optional control by Geiger‐Mu¨ller counters. Both machines employ baffles for removing turbulence from the cloud chamber; one uses a metal bellows, but no diaphragm; the other uses a thin rubber diaphragm and a bellows pump. Vacuum tube circuits control the timing of events connected with the expansion cycle. Stereophotographs are taken with flash bulbs, or with a spark illuminator that uses only 10 watts of power from an a.c. supply.

ISSN:0034-6748    

DOI:10.1063/1.1752066

出版商:AIP    

年代:1936

数据来源: AIP

摘要:

It is shown that the iron in the usual Weiss type of electromagnet is not as efficiently used as it might be whenever as intense fields as possible are desired. A design is proposed, consisting essentially of a small magnetizing coil completely surrounded by iron except for openings to the center of the coil where the magnetic field is produced.

ISSN:0034-6748    

DOI:10.1063/1.1752067

出版商:AIP    

年代:1936

数据来源: AIP

摘要:

In Part I of this article it is shown that the efficient use of iron in electromagnets is dependent on the design of efficient magnetizing coils. The characteristics of such magnetizing coils are discussed, and it is shown that the important factors are the shape of the coil, the power available, the distribution of current density, and the efficiency of cooling. Formulae applicable to coils of various types are derived, and the main features of an efficient design are determined.

ISSN:0034-6748    

DOI:10.1063/1.1752068

出版商:AIP    

年代:1936

数据来源: AIP