RSI Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue

Dec 1936

Volume 7, Issue 12, pp. 439-507

back to top
RSS Feeds

All in Good Proportion

H. A. B.

Rev. Sci. Instrum. 7, 439 (1936); http://dx.doi.org/10.1063/1.1752059 (2 pages)

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Abstract Unavailable
back to top
RSS Feeds

Increased Gamma‐Ray Sensitivity of Tube Counters and the Measurement of the Thorium Content of Ordinary Materials

Robley D. Evans and Raymond A. Mugele

Rev. Sci. Instrum. 7, 441 (1936); http://dx.doi.org/10.1063/1.1752060 (9 pages) | Cited 15 times

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Show Abstract
The useful sensitivity S of a tube counter exposed to feeble gamma‐radiation is proportional to (N−B)/(N+B)☒, where B is the background counting rate and N is the counting rate when the gamma‐ray source is present. S depends 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 sensitivity S may 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 12×10−7 g Th per g rock when only two hours of measurements are made on 1400 g of rock.

A Direct‐Reading Counting Rate Meter for Random Pulses

N. S. Gingrich, Robley D. Evans, and Harold E. Edgerton

Rev. Sci. Instrum. 7, 450 (1936); http://dx.doi.org/10.1063/1.1752061 (7 pages) | Cited 13 times

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Show Abstract
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.

Statistical Analysis of the Counting Rate Meter

L. I. Schiff and Robley D. Evans

Rev. Sci. Instrum. 7, 456 (1936); http://dx.doi.org/10.1063/1.1752062 (7 pages) | Cited 26 times

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Show Abstract
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 constant RC of the output tank circuit. This RC is analogous to a radioactive mean life and may be regarded as the mean memory time. While the output current depends only on the output resistance R, and not on the output capacitance C (except for very rapidly decaying sources), the statistical fluctuations in the output current depend upon RC, and are equivalent to the fluctuation expected in a time interval of 2RC. Expressions are derived for the condenser charge Q, or output current Q/RC, for constant and decaying sources of radiation, as well as for the expected fractional statistical fluctuations in these cases.

A Receiver for Radiometeorographs

A. V. Astin and L. L. Stockmann

Rev. Sci. Instrum. 7, 462 (1936); http://dx.doi.org/10.1063/1.1752063 (2 pages)

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Show Abstract
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.

A Universal X‐Ray Photogoniometer

Robert B. Hull and Victor Hicks

Rev. Sci. Instrum. 7, 464 (1936); http://dx.doi.org/10.1063/1.1752064 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Show Abstract
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.

Discrimination Between Partial and Total Coincidence Counts with Geiger‐Müller Counters

J. C. Mouzon

Rev. Sci. Instrum. 7, 467 (1936); http://dx.doi.org/10.1063/1.1752065 (4 pages) | Cited 2 times

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Show Abstract
A simple amplifier and recorder circuit for discriminating between partial and total coincidences of Geiger‐Müller counters is described.

Wilson Cloud Machines for Portable Use

Gordon L. Locher

Rev. Sci. Instrum. 7, 471 (1936); http://dx.doi.org/10.1063/1.1752066 (8 pages) | Cited 2 times

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Show Abstract
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‐Müller 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.

The Design of Powerful Electromagnets Part I. The Use of Iron

F. Bitter

Rev. Sci. Instrum. 7, 479 (1936); http://dx.doi.org/10.1063/1.1752067 (3 pages) | Cited 22 times

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Show Abstract
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.

The Design of Powerful Electromagnets Part II. The Magnetizing Coil

F. Bitter

Rev. Sci. Instrum. 7, 482 (1936); http://dx.doi.org/10.1063/1.1752068 (7 pages) | Cited 31 times

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Show Abstract
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.

An Improved Vacuum Tube Microammeter

A. W. Vance

Rev. Sci. Instrum. 7, 489 (1936); http://dx.doi.org/10.1063/1.1752069 (5 pages) | Cited 19 times

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Abstract Unavailable

Pendulum Magnetometer for Crystal Ferromagnetism. II

L. W. McKeehan, R. G. Piety, and J. D. Kleis

Rev. Sci. Instrum. 7, 494 (1936); http://dx.doi.org/10.1063/1.1752070 (4 pages) | Cited 3 times

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Show Abstract
Improvements in the method of preparing spheroidal specimens, in the suspension of the pendulum, in the method of measuring its displacement, and in correcting for the field gradient due to the magnetizing solenoid are reported. New means for protecting small specimens from atmospheric action without rigid constraint and up to the softening temperatures of Pyrex glass (or of fused silica) are described.

A Thyratron‐Controlled Ionization Gauge

J. Barton Hoag and Nicholas M. Smith

Rev. Sci. Instrum. 7, 497 (1936); http://dx.doi.org/10.1063/1.1752071 (3 pages) | Cited 8 times

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Show Abstract
A thyratron is used to maintain constant the ionizing electron current in an ionization gauge. A circuit operating entirely from the alternating current supply line is given, together with the constants found suitable in the particular apparatus used and including provision for outgassing the metal parts of the gauge. The thyratron control was found to maintain constant electron current over the usual pressure range and with line voltage fluctuations of ±6 percent.

A Coercimeter for Magnetically Weak Materials

E. V. Potter and E. F. Coleman

Rev. Sci. Instrum. 7, 499 (1936); http://dx.doi.org/10.1063/1.1752072 (3 pages)

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Show Abstract
A form of coercimeter based on that of Davis and Hartenheim is described. By altering constructional features and using a direct‐coupled thermionic amplifier and microammeter for indicating balance, the accuracy and sensitivity of measurements on the coercive force of magnetically weak materials like slags are improved. A stable two‐stage amplifier makes the balance indication more sensitive by a factor of about 200. The range of application of the instrument is thus also extended to alloys of very low coercive force and to cases where the available sample is very small.
back to top
RSS Feeds

Stirring Mechanism for Precision Thermostats

S. C. Collins

Rev. Sci. Instrum. 7, 502 (1936); http://dx.doi.org/10.1063/1.1752073 (1 page) | Cited 2 times

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Abstract Unavailable
FREE

Erratum: A Method for Blackening Brass

David W. Mann

Rev. Sci. Instrum. 7, 503 (1936); http://dx.doi.org/10.1063/1.1752074 (1 page)

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Abstract Unavailable

A Note on the Melcher‐Nutting Method for the Measurement of the Total Porosities of Consolidated Sands

Morris Muskat

Rev. Sci. Instrum. 7, 503 (1936); http://dx.doi.org/10.1063/1.1752075 (1 page)

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Abstract Unavailable

PHYSICS NEWS

Rev. Sci. Instrum. 7, 504 (1936); http://dx.doi.org/10.1063/1.1752076 (4 pages)

Online Publication Date: 29 December 2004

Full Text: | Download PDF

Abstract Unavailable
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close