Pear Shaped Crookes Tube

(Also known as Hittorf Tube)

Instead of having the electrodes “in line” on the opposite sides of the tube, as in the early Crookes tube, the cathode in this tube is a flat aluminum plate on the narrow side of the “pear” while the anode is “rod shaped” in a secondary lateral tubular chamber on the larger side. The other tubular extension is for the vacuum.

It is while experimenting with a similar tube that Röntgen incidentally discovered X-Rays late in 1895. These rays, of an unknown nature yet, were produced by a large area of the glass wall on the wider side of the tube, by the impact of the unfocused “cathode rays” (electron beam). This large size of the x-ray source accounts for the lack of sharpness of the earliest x-ray “photographs”.

Such tubes were soon abandoned for the production of X-rays, and replaced by what came to be known as “the focus tube”.

This particular tube is a late 20^th Century replica, offered by Siemens.

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