From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The properties and superiority of Neon gas in discharge lamps compared to other gases.
| Identifier | ExFiles\Box 79\1\ scan0261 | |
| Date | 19th February 1930 | |
| - 5 - R.R. 286A (100 T) (S.G. 643. 19-2-30) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2618 tubes is invariably associated with sputtering of the electrodes which, at high pressures, only takes place when the gas is spectroscopically free from chemically active gases. It is generally supposed that the gas so disappearing remains embedded or adsorbed in the layer of sputtered aluminium on the sides of the tube near the cathode, the idea of true chemical combination not being acceptable without very rigorous proof. In order to obtain information on this point, a completely run out specimen of the first batch of lamps, which was of course very heavily sputtered, was taken for test. First the sputtered cathode end was gradually heated to near the softening point of the glass (when it cracked) without any substantial or apparent increase in the internal pressure of Neon. The end was then cut off, broken into small pieces and heated in a quartz tube in a high vacuum apparatus provided with a spectrum tube. At a temperature about the softening point of the glass a good deal of gas was released which showed the hydrocarbon spectrum (but may nevertheless have contained some Neon as this is easily masked); this gas was pumped off and on heating further to a red heat, as the glass started to melt, Neon was given off, the spectrum showing quite clearly. Apparatus for measurement and analysis of the gas so released was not available, but it is hoped to repeat this interesting experiment, which shows definitely that the Neon is contained either in the sputtered aluminium or very near the surface of the glass so that it is released by heat. USE OF OTHER GASES INSTEAD OF NEON. Ordinary chemically active gases give very feeble illumination, CO being about the best. Helium gives a bright discharge but not nearly so valuable in quality for visual work as Neon; its presence as an impurity in the latter gas renders the discharge more rosy red but up to 10 per cent does not affect its brightness seriously. Mercury vapour as used by C. T. R.{Sir Henry Royce} Wilson in his photography of ionisation tracks would probably give very bright flashes, but the fact that the lamp has to be kept very hot is a serious objection. REASON FOR SUPERIORITY OF NEON. The brilliant orange-red glow of the discharge in Neon is composed almost entirely of lines in the region 5700-6700 a.u. and is in such striking contrast to sunlight that stroboscopic observations can even be done in broad daylight if necessary, the ordinary appearance of the rotating disc having merely a grey background added, looking bluish by contrast. The actual amount of light radiated per unit of energy i.e. the real efficiency of the discharge in Neon, is not markedly greater than that in e.g. mercury vapour, but the apparent efficiency is enormously enhanced by the fact that it consists so largely of red light. Victor Henri and J.{Mr Johnson W.M.} L. des ( Contd. ) | ||