X-RAY MICROSCOPY 



Table 1. Mass Absorption Coefficients for Some Useful Ultrasoft Wavelengths 

 Derived Semiempirically' with a Probable Error of About ±2% 



Zapon (H 5.3%, C 46.7%, N 6.6%, O 41.4%), Parlodion (H 3.6%, C 28.1%, N 11.5%, O 56.8%), Animal 

 Proteins (H 7%, C 52.5%, N 16.5%, O 22.5%o, S 1.5%) 



tron beam will be prevented from ever 

 reaching the target and exciting the desired 

 characteristic radiation. This primary re- 

 quirement has been met in two ways, as is 

 illustrated in Fig. 5. 



Tungsten contamination has been elimi- 

 nated by placing the tungsten coil emitter 

 below the target and by electrostatically fo- 

 cusing the electron beam along a circular 

 path to the target surface. In order to avoid 

 the space charge limiting of the beam current 

 which usually accompanies the "hiding" of 



the anode from the emitter, a special grid at 

 anode potential has been employed. 



The carbonaceous depositing under the in- 

 teraction of the electron beam and hydrocar- 

 bon vapors at the target has been minimized 

 by maintaining a vacumii of about 10~® mm 

 pressure, using water-cooled baffles and a 

 charcoal trap between the oil diffusion pump 

 and the x-ray source. A sample may be intro- 

 duced without contaminating the x-ray 

 source by using a separately evacuated cam- 

 era and a vacuum isolation gate which is 

 used to introduce a thin filter-window to the 



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