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A reciprocating apparatus for detecting ionizing rays
534
V. S. BUREAU OF STANDARDS NOTES.
[J. F. I.
but the specifications for them are practically unchanged from those given in previous editions of this circular. These specifications have been prepared primarily for the use of the departments of the government in purchasing incandescent lamps, but it seems desirable, on account of the thoroughness with which the subject has been studied and discussed, that the specifications should be available to the general public. They are, therefore, being issued as the ninth edition of Bureau of Standards Circular No. 13, and copies may be obtained on application to that Bureau. Criticisms and suggestions concerning these specifications and lamp ratings are invited from both manufacturers and users of lamps. All such suggestions will be carefully considered when the specifications are again revised.
A Reciprocating Apparatus for Detecting Ionizing Rays.
TAKEO SHIMIZU. (Proc. Roy. Soc., A. 7oo.)--Mr. C. T. R. Wilson, of Cambridge, years ago devised a very elegant method of making visible the paths of ionizing particles in gases. Air containing water vapor was expanded suddenly and the vapor condensed upon the ions. The path of an alpha particle was a streak of cloud, the droplets of which had formed around the ions caused by the collisions of the particle. Mr. Shimizu has modified the method so that the expansion is produced twice a second along w'ith the application of an electrostatic field for a known part of the stroke. A reciprocating mechanism operates the piston governing the expansion. For a study of the path of each track the Wilson apparatus is superior. It is, however, claimed that the newer form is more sensitive .and by the periodic recurrence of the stroke it is possible to study the time of the origination of the rays producing the traces. Mr. Shimizu has used his device to investigate the products of collisions with alpha particles. Sir Ernest Rutherford states that among IOO,OOO alpha particles from radium C passing through air there will be one making close collision with an atomic nucleus so as to produce a rapidly moving atom. A moving picture film recorded the tracks as seen from two positions at right angles to each other. In the 3ooo tracks photographed 35 spurred tracks were found, but their explanation and interpretation remains for the future. Owing to this recently devised apparatus it has thus become possible to have a registration at half-second intervals, if not continuously, of what goes on in air subject to the bombardment of ionizing particles. This field of investigation is thereby advanced to an extent comparable to the progress introduced into other fields upon the employment of continuously recording methods. G. F. S.
V. S. BUREAU OF STANDARDS NOTES.
[J. F. I.
but the specifications for them are practically unchanged from those given in previous editions of this circular. These specifications have been prepared primarily for the use of the departments of the government in purchasing incandescent lamps, but it seems desirable, on account of the thoroughness with which the subject has been studied and discussed, that the specifications should be available to the general public. They are, therefore, being issued as the ninth edition of Bureau of Standards Circular No. 13, and copies may be obtained on application to that Bureau. Criticisms and suggestions concerning these specifications and lamp ratings are invited from both manufacturers and users of lamps. All such suggestions will be carefully considered when the specifications are again revised.
A Reciprocating Apparatus for Detecting Ionizing Rays.
TAKEO SHIMIZU. (Proc. Roy. Soc., A. 7oo.)--Mr. C. T. R. Wilson, of Cambridge, years ago devised a very elegant method of making visible the paths of ionizing particles in gases. Air containing water vapor was expanded suddenly and the vapor condensed upon the ions. The path of an alpha particle was a streak of cloud, the droplets of which had formed around the ions caused by the collisions of the particle. Mr. Shimizu has modified the method so that the expansion is produced twice a second along w'ith the application of an electrostatic field for a known part of the stroke. A reciprocating mechanism operates the piston governing the expansion. For a study of the path of each track the Wilson apparatus is superior. It is, however, claimed that the newer form is more sensitive .and by the periodic recurrence of the stroke it is possible to study the time of the origination of the rays producing the traces. Mr. Shimizu has used his device to investigate the products of collisions with alpha particles. Sir Ernest Rutherford states that among IOO,OOO alpha particles from radium C passing through air there will be one making close collision with an atomic nucleus so as to produce a rapidly moving atom. A moving picture film recorded the tracks as seen from two positions at right angles to each other. In the 3ooo tracks photographed 35 spurred tracks were found, but their explanation and interpretation remains for the future. Owing to this recently devised apparatus it has thus become possible to have a registration at half-second intervals, if not continuously, of what goes on in air subject to the bombardment of ionizing particles. This field of investigation is thereby advanced to an extent comparable to the progress introduced into other fields upon the employment of continuously recording methods. G. F. S.