. The principles and practice of roentgenological technique . ch is allowed to spark. 5. Marked and frequent changing of theenergizing current during exposure. 6. Considerable quantities of inverse. COOLIDGE TUBE In this tube, as in the gas tube, the cathodestream is a cone with its apex at the result is obtained, because the molybde-num cylinder bears a negative charge and re-pels electrons in their flight. The position ofthe cylinder determines whether the streamstrikes the target at a point or at a small areaand whether, therefore, the tube is finefocus or broad focus. Under nor
. The principles and practice of roentgenological technique . ch is allowed to spark. 5. Marked and frequent changing of theenergizing current during exposure. 6. Considerable quantities of inverse. COOLIDGE TUBE In this tube, as in the gas tube, the cathodestream is a cone with its apex at the result is obtained, because the molybde-num cylinder bears a negative charge and re-pels electrons in their flight. The position ofthe cylinder determines whether the streamstrikes the target at a point or at a small areaand whether, therefore, the tube is finefocus or broad focus. Under normal working conditions there isno apparent movement of the focal point in aCoolidge tube except in exposures under stress,as for instance when 100 mills, with 1 inchgap or 20 mills, with 9 inch gap are used. The active Coolidge tube may be studiedphotographically by means of its own radia-tion bv a pin-hole opening in a lead box. Thecamera used by Coolidge has a inches in diameter; the distance fromthe long axis of the tube to the pinhole is. Fig. 112.—Pin hole camera Roentgenogram of frontand back of target, showing the emission ofx-rays from all points, except working face,to be of same intensitj. (Coolidge.) 15 in., and the distance from the pinhole tothe photographic plate is 5 inches. In the length views of the target the tube was soplaced that the neck of the target was directlyopposite the pinhole (see Fig. 110). Theplate was in a closed box made of lead J/s inchthick. The tube was energized by a voltagecorresponding to a 7 in. spark gap between
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectradiogr, bookyear1920
