PHOTOELECTRIC PROPERTIES OF lONICALLY BOMBARDED SILICON 813 



projected along the barrier plane and not normal to it as in the. latest 

 units, SO that with the rapidly increasing transparency in this region, 

 less infra-red radiation was lost. However, the blue was rapidly at- 

 tenuated. 



When illuminated by tungsten hght of 2848°K color temperature, the 

 large B cells gave 2160 microamps per lumen and the C unit 638. Cor- 

 recting for a surface reflectance of 0.385, the net sensitivities would be 

 3510 and 1040. These measurements were made with between 4- and 

 5-footcandles illuminance on the cells, a region in which the response is 

 proportional to the intensity. At much higher values of illuminance there 

 was some falling off of response so that the effective sensitivity was a 

 little lower. The above measurements were made on a ten ohm microam- 

 meter which is too low a resistance to affect the linearity. The inter- 

 mediate cells ran approximately 3000 microamps per lumen in the most 

 sensitive region of bombardment without correction for surface reflec- 

 tion and at 10- to 20-footcandles for the same tungsten lamp using a 

 meter of 76 ohms. 



0.6 



0.5 



0.6 0.7 O.S 0.9 1.0 



WAVELENGTH IN MICRONS 



Fig. 11 — Spectral response of large size photocells of B and C grades of silicon. 



