THE MEASUREMENT OF X-RAY INTENSITIES AS FUNCTIONS OF VOLTAGE, UP TO 180 KV

Abstract

The measurement of intensity of an x‐ray line presents two sets of technical requirements, quite different, according to whether the intensity is to be compared with those of other lines at the same voltage or of the same line at other voltages. The latter set of requirements is discussed here, with a description of a tube designed to meet them. This tube is built of steel and Pyrex, with several sections of each, permitting a variety of high‐voltage connections for special purposes related to possible sources of error. To prevent the deposition of carbon and tungsten on the target, the pumping speed is made very high, especially for grease vapors. The detection of carbon, and rough measurement of its retardation of the cathode rays, is accomplished by one of the special changes of connections. To minimize the effects of such positive ions as may be present in spite of the high pumping speed, the tube has a special form of cathode. And to measure the possible amount of error due to such ions, another of the special connections transforms the cathode‐ray chamber of the tube into an ionization gauge. Finally a third change of connections makes it possible to wear out the sources of minute field currents, that would otherwise cause errors in x‐ray intensity measurements.