Early Basic Type Crookes Tube

Ref. A1

This undated tube measures 10.5” (26 cm) long.

The glass extension and the stopper on the underside of the tube, allow the introduction of different gases inside the tube, as well as the control of the vacuum.

The electrodes were connected to a high voltage generator (induction coil or electrostatic machine). The variations of the visible cathode beam between the electrodes were studied according to the voltages applied, according to the degree of vacuum, and according to the nature of the residual gas.

“…The tube itself should be free from flaws. The walls should be kept as thin as is compatible with the great atmospheric pressure. Both the cathode and the anode are flat discs of aluminium since this is the only metal which does not appreciably disintegrate under the influence of the electric discharge. Owing to the difference in the coefficient of expansion of glass and aluminium, the latter must be fused to platinum wires which are sealed into lead glass, and these again are fused together with the glass of the tube proper. The terminals ought not to be the ends of the platinum wires bent into rings or hook-shape, but should be soldered to metal cups cemented to the glass….”

(A.W. Isenthal & H. Snowden Ward, “Practical Radiography”, 1898, p.55).

Sir William Crookes (1832-1919)