✍ Scribed by A.W. Hull
No coin nor oath required. For personal study only.
By A. W. Hull.1 THIS article is a first report of work upon the accurate measurement of the quality and intensity of X-rays from a standard and exactly reproducible X-ray tube.
A Coolidge tube is excited ,by a voltage of Ioo,ooo, boosted from the ISO-volt , 2ooo-cycle alternating current of the mains by a transformer, and rectified by kenotrons.
Oscillations are smoothed out by inductance, and capacity until .the voltage variations are less than a per cent. for 5 kilo,watts and are still smaller for loads below 5 kilowatts.
The spectrometer is of the usual form, with a crystal o.f rock salt or Iceland spar substituted for the. prism, and an ionization chamber in p.lace of a photometer.
Wave-length and intensity values for the X-ray spectra from a tungsten target at five different vo.ltages from 2o,oo0 to 4o,ooo are. plotted, and show a very rapid decrease in wave-length, with rise in voltage, and at the same time an increase in intensity for all wave-lengths. Hence a penetrating ray free. from soft radiations can be obtained only by using a filter exhibiting selective a4bsorption for 'the latter. Measurements of the spectrum at 7o,ooo volts with and without a filter of 3 ram. of aluminum indicate that the intensity of the soft rays has been reduced much more than that of the penetrating, but there, is still a great deal of the former left. Use of still heavier filters to further reduce the intensity of soft rays would also cut down the intensity of the penetrating rays to a small fraction, 'but with a very powerful tube, such as in process of development, there may yet be left sufficient for practical work. It is also hoped that by use of some special target material giving a powerful radiation of a particular wavelength it may be possi,ble to o'btain still purer " monochromate " * Communicated by the Director.
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