Early Tube Electrodes

Ref. L2

Two “heavy” copper anti-cathodes, with a centrally embedded tungsten target.   Note the partly molten and severely crackled target in one of these anti-cathodes, due to extreme overheating.

The anti-cathode to the right in the upper picture is wholly made of Tungsten and comes from an old 32” (80 cm) long, of unknown make Coolidge type therapy tube.

Note the 45 degree angle of the targets denoting they date before the “line focus” era, probably to the second decade, or early twenties of last century.

Three aluminium cathodes salvaged from old broken gas discharge tubes. Note the severe discoloration on two of them.

The Line Focus Target

(Introduced in the twenties in hot cathode Coolidge type tubes)

In the “line focus” target the target angle is reduced and the source of radiation is no more a central “spot” on the target, but a linear source which, seen from the patient side of the tube, looks like a small spot source, about a 3 mm square, resulting in sharper X-ray images with an improved heat loadability of the target. (see also the “Media” Line Focus Tube).