.
_
9—3,
HO”DCATHODE X-RAY TUBES
195
change of target material and lament replacement are important.
Tubes are also designed in such a manner that the focal spot is
rectangular instead of circular. This permits larger X—ray intensity
without destruction of the target.
_
_
In gure 9—3, the high voltage is supplied by the transformer
T2 (20 to 2000 kV.) and is often rectiéd by a diode -R in order
produce a steadier and more homogeneous beam of X—rays; The
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