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244 D. B. JOY [j. s. M. P. E.
motion pictures and photographing motion pictures with projected backgrounds, it would be desirable to have available a light-source of the same dimensions as the present 13.6-mm. carbon but capable of giving a considerably greater amount of light and a more uniform distribution across the projection screen.
The new super-high-intensity 13.6-mm. carbon has been designed to meet these requirements. It has the same outside diameter as the regular 13.6-mm. carbon but has a much larger core. Its design and composition are such that it will burn steadily at currents of 140 to 190 amperes. At the lower current the crater is comparatively shallow, but at the higher currents it is considerably deeper than that of the regular carbon.
The consumption of the carbon at various currents, compared with that of the regular 13.6-mm. carbon, is given in Table I. The maxi
TABLE I
Consumption of Regular and Super 13.6-Mm. Carbons at Same Arc Setting
Consumption Carbon Current Voltage (Inches per Hour)
Regular 13.6-mm. 120 64 11.3
Regular 13.6-mm. 130 68 15.5
Super 13.6-mm. 140 60 12.6
Super 13.6-mm. 160 66 18.0
Super 13.6-mm. 180 72 25.5
mum current-carrying capacity of the regular carbon is 130 amperes. In contrast to this, the super-high-intensity carbon gives a very steady light at much higher currents and consumption rates than the regular carbon. It can be anticipated, because of the larger core size and higher consumption, that the intrinsic brilliancy would be both higher and more uniformly distributed across the crater face than in the case of the regular 13.6-mm. carbon.
Measurements of the intrinsic brilliancy across the crater face are given in Fig. 1. The curves show that at 180 amperes the intrinsic brilliancy of the super-carbon crater is noticeably higher than that of the regular carbon crater at its maximum current of 130 amperes. It is also evident that with the super-carbon the tapering of the intrinsic brilliancy from the center to the sides of the crater is less. For example, at a distance of 3 millimeters from the center, the