Research with Gas Discharge Tubes Continues

When a high voltage is applied to electrodes in a partially evacuated glass tube, a colorful glow is often produced. This phenomenon has now been studied by scientists for over 50 years.

In 1838 Michael Faraday described the characteristics of the glow which was separated into bright regions near the electrodes and a dark region (the Faraday dark space) in between. In the mid-1800's the very creative glass-blower Heinrich Geissler began to produce low-pressure gas tubes in a variety of sizes, shapes, and interesting configurations. These multi-colored glowing tubes are attractive pieces of art and useful sources of light.

The physicist Johann Hittorf has observed that in some tubes glowing rays extend from the negative electrode and produce a fluorescent glow where they strike the glass walls of the tube. In 1876 these were named "cathode rays" by Eugene Goldstein. A few years later William Crookes used tubes which he designed to demonstrate that cathode rays would cast shadows of objects and turn a small metal wheel in their path and could be deflected by a magnet.

In 1892 Heinrich Hertz demonstrated that cathode rays could penetrate very thin metal foil. He encouraged his student, Philip Lenard, to continue this research. Lenard developed a tube with a thin foil window through which the cathode rays could pass into the atmosphere. He studied the penetration of these rays through various materials.

Many types of gas discharge tubes are now available from manufacturers and are being used for research in physics laboratories and for demonstrations and entertainment.

One of the physicists who is currently conducting investigations with gas discharge tubes is Professor Wilhelm Roentgen of the University of Wurzburg. He is conducting experiments with a variety of tubes including those of the Crookes, Hittorf, and Lenard designs. He is investigating whether cathode rays can penetrate the glass walls of the tubes. His laboratory is equipped with a powerful Ruhmkorff coil for providing the high electrical potential for the experiments.

Notice

It is expected that there will be special edition of The X-ray Century on November 9, to report on a significant event.