Cylindrical Focus Tube

Ref. B5

This is a 10” (25 cm) long, 1.5” (37 mm) diameter, three-electrode tube.

It has an aluminum rod anode, a concave aluminum cathode and a thin platinum anti-cathode target deformed by the intense heat generated by the impact of the electron beam.

It features looped platinum wire external connections. There is also glass discoloration on the anode side of the tube due to use.

The undated tube is of unknown make, but judging from the thin bare square-shaped platinum target it should be of about the same period as the Jackson focus tube (1896). In later makes of tubes the thin platinum target is round in shape and embedded in a metal support (e.g. the bulbar focus tube).