THE X-RAY K-RADIATION OF TUNGSTEN. 
ELMER DERSHEM. 
Metals of the greater atomic weights can he made to emit at 
least two types of characteristic X radiations, known as the L 
or soft and the K or hard radiations. In a previous paper* the 
wave lengths of the known lines in the L region of the tungsten 
X-ray spectrum were given. The work has since been extended 
to the characteristic lines of the K region. 
The method of performing this work was the same as de- 
scribed in the previous paper except that a higher potential had 
to be applied to the X-ray tube in order to excite the K rays 
and the photographic plate placed at a greater distance from 
the reflecting crystal of rock salt in order to secure sufficient 
deviation for accurate measurement. 
Pig. 26 — K-Radiation Spectrum of Tungsten. 
The accompanying photograph shows the K region to contain 
four distinct lines grouped in two pairs. The first orders on 
each side of the center line are shown in the photograph. 
In order to obtain a clear and sharply defined photograph of 
these X-ray spectral lines it is -required that the source should 
be very narrow and the distance between the crystal and photo- 
graphic plate as great as is consistent with the securing of 
measurable intensity and also that the crystal should be quite 
thin in order that the reflection of the rays may not occur at 
varying depths below the surface of the crystal and cause a 
widening of the reflected beam. 
These conditions lead to a long exposure and the latter will 
cause a fogging of the plate due to the secondary radiation ex- 
*The Tungsten X-Ray Spectrum, Iowa Academy of Science, Proceedings 
Vol. XXIII, pp. 191-3. 
