. The principles and practice of roentgenological technique . exposure is made similar tothat obtained when an ordinary tube is shifteda distance of six centimeters. II. Tlic zvriatious in inctliods of coolinghave resulted in the production of severaltypes of tubes. ^ The \\ater-Cooled Tube In this tube the target is cooled by water(Fig. 75). The tai-get forms the bottom ofa small metal cup which is fixed to a glasssleeve provided with an expanded portionwhich acts as a reservoir. Those modelsare best in which the target, consistingof platinum, forms the floor of the water con-tainer. They are
. The principles and practice of roentgenological technique . exposure is made similar tothat obtained when an ordinary tube is shifteda distance of six centimeters. II. Tlic zvriatious in inctliods of coolinghave resulted in the production of severaltypes of tubes. ^ The \\ater-Cooled Tube In this tube the target is cooled by water(Fig. 75). The tai-get forms the bottom ofa small metal cup which is fixed to a glasssleeve provided with an expanded portionwhich acts as a reservoir. Those modelsare best in which the target, consistingof platinum, forms the floor of the water con-tainer. They are of value when continuedusage over long periods is necessary, as influoroscopy or therapy. A modification of-this tube, wherein, instead of a reservoir, aspray of water is maintained against the targethas had its vogue. The Oil-Cooled TubeIn this tube the x-ray bulb is enclosed byan enveloping chamber into which oil isplaced; this oil, by cooling the anode and cath-ode and glass bulb, maintains the vacuum at aconstant point. At the same time the oil in the. Fig. 79.—Air-cooled target with radiator. COOLING METHODS 65 enveloping chamber filters the very softestrays. The x-ray tube itself is equivalent to a15-cm. bulb, and is of oval form, permittingthe target to be placed in close proximity tothe body. The window through which the oil is pouredis closed by caps made of different materialsfor filtration. The enveloping glass shieldmay be of lead glass. The Air-Cooled Tube Air is forced by means of a pressure pumpthrough inlet tubes set in the hollow cathodeand target. The latter is massive and of cop-per. The tungsten button is set into it, sothat it forms the floor of the hollow effective cooling of the cathode preventsthe progressive hardening of the tube. III. Tlic rariatioiis in iiicthods of reduc-ing or raising the vacuum have producedseveral types of tubes. There are fourmethods for maintaining the desired workingvacimm.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectradiogr, bookyear1920
