696 



TABLE 772.— PRIMARY PROTECTIVE-BARRIER REQUIREMENTS FOR 



1000-KILOVOLT CONSTANT POTENTIAL WITH 



TRANSMISSION TARGET* 



Barrier thicknesses with target current of — 



Target 



distance 



ft 



5( 1.52 m) 



10 ( 3.05 m) 



20 ( 6.1 m) 



100(30.5 m) 



* For reference, see footnote 237, p. 693. 



t These concrete thicknesses are for a concrete density of 147 pounds per cubic foot. 



TABLE 773.— FILTERS FOR OBTAINING MONOCHROMATIC X-RAYS* 



* For reference, see footnote 236, p. 692. 

 TABLE 774.— CRITICAL ABSORPTION WAVELENGTHS (A), L SERIES* 



Element (^-u) ^21) (L B ) 



47 Ag 3.2474 3.5067 3.6908 



53 I 2.3839 2.5475 2.7139 



56 Ba 2.0620 2.1993 2.3568 



74 W 1.0205 1.0713 1.2116 



L, Ljj L m 



Element {^vl) (^n) (^22) 



78 Pt 8921 .9321 1.0709 



82 Pb 7806 .8136 .9500 



92 U 5687 .5920 .7216 



* For reference, see footnote 236, p. 692. 

 TABLE 775.— CRITICAL ABSORPTION WAVELENGTHS (A), M SERIES* 



* For reference, see footnote 236, p. 692. 

 TABLE 776.— CHARACTERISTIC EMISSION WAVELENGTHS (A). K SERIES* 



Element 7 (ft) 



24 Cr 2.0667 "(jS.) 



26 Fe 1.740800%) 



28 Ni 1.48561 



29 Cu 1.37824 



42 Mo 619698 



45 Rh 53396 



47 Ag 486030 



74 W 17899 t 



78 Pt 15887 



* For reference, see footnote 236, p. 692. 

 t 8 = 0.17803, 5 2 = 0.17917 (Duane, 1933). 



SMITHSONIAN PHYSICAL TABLES 



