13. An Automatic ‘‘make and break’’ Key for Actuat- 
ing the Heating and High Potential Circuits of a 
Coolidge X Ray Tube. 
By E. P. Harrison, Ph.D., F.B.S.E., F.Inst.P. 
and 
NARENDRA NATH SEN. 
In using a Coolidge tube for operations (such as photo- 
graphy of a Lane diffraction pattern) in which the tube has to 
be “run”? for considerable periods with currents greater than 
3 milliampere and during which the anticathode may become 
seriously overheated it is convenient to allow the tube short 
periods of rest for cooling. To eflezt automatic © make 
“break” of the three circuits (heating, interruptor and coil- 
wort cincUtT 
eeu INTERRUPTE 


SEATING CIRCUIT ae con, PRIMARY 
cracuit 
ip ce mes 
: : been devised. 
primary) the apparatus described below has j 
By its use it is possible to run a Coolidge tube carrying & rage 
current without attention for an indefinitely long time a 
with no risk of overheating. ya oS . 
uppose it is desired to run the tube for 5 ee 
cool it for 10 minutes; run it for 5 minutes, once mor 
it for 10 minutes, and so on. 
