Neon Lamp Research Articles

A new photo-electric and ionisation effect

For the discharge in a neon lamp to start a certain minimuni voltage is necessary. This voltage is found to be affected very considerably by light or other ionising agents external to the lamp. This effect is believed not to have been previously recorded. The writers have investigated the light effect in some detail, and record that it is produced by illumination of any intensity above a very low value (0.01 foot-candles producing an appreciable effect), that it is caused by rays of a broad wave-band in the visible spectrum, with a maximum effect in the orange, and that the seat of the effect is located on the surface of both the metal electrodes, irrespective of polarity. A similar effect, but one whose mechanism is believed to be different, is found to be caused by rays from uranium oxide and from an X-ray tube. In the latter case it was extremely well marked, so that it is possible to detect by this means X-rays from a very feeble tube at a distance of 90 feet. Certain practical applications of this effect are suggested.

Moving striations in neon and helium

During some work on Neon Lamps for Stroboscopic Work, it was noticed that, when the flash of an ordinary spectrum tube containing neon was analysed by a rotating mirror, it consisted of two parts, an extremely short flash followed by a flame or arc, and that the latter consisted of bright striations travelling from anode to cathode. The same phenomenon was observed with helium. The velocity of these striations was roughly measured, and found to be about 50,000 cm./sec. in neon and 100,000 cm./sec. in helium. As these figures approximated to the velocities of sound in these gases, it was hoped that investigation of the phenomenon might lead to an explanation of striations generally. This expectation has, unfortunately, not been realised, for these velocities were soon found to be special or limiting cases of far more complex phenomena. The following paper is an account of the preliminary experiments, which have given interesting, but somewhat inconclusive results. The first account of moving striations observed by means of a rotating mirror is given by A. Wüllner.† They were investigated more fully by W. Spottiswoode. Both these observers used several elementary gases then available, but most of Spottiswoode’s results were obtained with compounds, these giving more definite striations. Unfortunately, neither observer recorded any figures for the velocities, but Wüllner mentions that his mirror was rotated at ½ to 2 revolutions per second.