An Application of Geiger Counter Tubes for Spectrochemical Analysis

S OF RECENT SCIENTIFIC PUBLICATIONS OF THE N.V. PHILIPS' GLOEILAMPENFABRIEKEN Reprints of these papers not marked with an asterisk can be obtained free of charge upon application to the Administration of the Research Laboratory, Kastanjelaan, Eindhoven, Netherlands. . spark will contain the lead line at 2203A. By a small quartz specirograph provided with a movable slit in its focal plane, this spectral line is isolated and its intensity is measured by a photoelectric Geiger counter tube with counting rate meter. The sensitivity of the apparatus in normal operation is limited to about 0.60mg lead per m3 air, by the fluctuations of the background intensity emitted by the spark. Although this is more than the maximum permissible concentration of lead 1857: A. Bierman: A new type of betatron without an iron yoke (Nature London 163, 649, 1949, April 23). A new type of betatron is described in which the magnetic field, is obtained by .means 'of coils in air, through. which the discharge current of a 6.5 (LF condenser battery passes. There is only a small iron core, by means of which it is easy to fulfil the "flux condition". Saturation of the core . Jffects contraction of the orbits towards the end of the, acceleration period, until the electrons strike a tungsten target 0.1 mm thick. The betatron as a whol~ weighs no more than 50 kg, the iron core itself weighing less than 5 kg. The peak value of the magnetic induction is 0.4 Wh/m2 (4,000 gauss), the radius of the orbit 8 cm; the energy of the accelerated electrons amounts to 9 MeV. Cf. Philips Techn. Rev. 11, 65-78, 1949 (No. 3). 1858: J. A. Haringx: Het merkwaardig gedrag van op druk belaste schroefveren (Voordrachten Kon. Inst. Ingenieurs 1, 298-313, 1949, ,No. 3). (The remarkable behaviour of compression-Ioaded helical springs; in