. Journal of radiology . centimeter of absorbing mate-rial whose absorption coefficient ism for the rays considered, for atime T is T Q N0 F emd N== 4tiR2 This equation holds in generalfor inhomogeneous beta rays andfor homogeneous x-rays andgamma rays. The constant N0must be determined once for all,for any particular source of equation is dependent on theuse of a point source of focal spot on the anticathode, Page Eighi and the short emanation tubesused in practice fulfill this re-quirement to a sufficient degree ofapproximation. For more thanone source the effect may b
. Journal of radiology . centimeter of absorbing mate-rial whose absorption coefficient ism for the rays considered, for atime T is T Q N0 F emd N== 4tiR2 This equation holds in generalfor inhomogeneous beta rays andfor homogeneous x-rays andgamma rays. The constant N0must be determined once for all,for any particular source of equation is dependent on theuse of a point source of focal spot on the anticathode, Page Eighi and the short emanation tubesused in practice fulfill this re-quirement to a sufficient degree ofapproximation. For more thanone source the effect may be com-puted by adding the effects of thevarious sources. The alpha particles from radiumconsist of five different groups,having very definite ranges lyingbetween 3 and 6 centimeters inair. The ionization by these isnearly constant over their range,and they lend themselves easilyto computation by the equationabove if we omit the emd factorwhich is not applicable to particlesionizing uniformly. T\a lNUrRt&u/m ,«. On the basis of reasoning ofthis sort I have roughly computedand arranged graphically, thecourse of the ionizing action ofthe alpha, beta, gamma rays ofradium, and x-rays, omitting thefactor F which depends on datawhich were inaccessible to is illustrated in Figs. 2, 3, PHYSICAL ACTIOX OF RADIUM AND X-RAYS—LOEB 4, and 5. Fig 2 represents theionization due to alpha particlesfrom 1 milligram of radium. Thetotal number of ions produced inthat portion of the cone generatedby the point source of radium anda circular area of 1 square centi-meter at 1 centimeter from theradium, below this surface is 1012 ions. These ions are gen-erated nearly uniformly through-out a depth of .058 millimeter be-low the surface, a very minutedistance indeed. The total ioniza-tion is about X 1014 ions percubic centimeter for this feebledepth. There is no doubt butthat these rays are the most pow-erful ionizers of all radiationsThey are, however, obviously im-practical fo
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