Incandescent Filament Research Articles

Optical Depth Gauge for Laboratory Studies of Water Waves

The absorption of infrared light by water is used to measure depth. A collimated beam of light from an incandescent filament source is projected through the water from below, filtered, and detected by an infrared sensitive phototube. The quantitative performance of the gauge is assessed, and the effects of refraction and reflection at the the free surface are discussed. A circuit that linearizes the exponential dependence of the phototube output on depth is described. The sensitivity of the gauge and linearizing circuit is determined by calibration to be about 0.05 V/cm, and the smallest measurable wave amplitude, corresponding to unity signal-to-noise ratio, is about 0.07 mm. The accuracy for absolute depth measurement is about ½ mm.

Preparation of polymeric products from p-xylene, 1,2,4-trimethylbenzene, and 4,4?-dimethylbibenzyl

1. Polymeric compounds were prepared by the thermal polydehydrocondensation of p-xylene, 1,2,4-trimethylbenzene, and 4,4′-dimethylbibenzyl, which was effected by the pyrolysis of these compounds on an incandescent metal filament immersed in the liquid monomer. 2. The effect of temperature and time on the yield of polymeric products was investigated. 3. The structures of the polymers obtained were investigated with the help of an analysis of their infrared spectra. 4. The probable mechanism of the formation of the polymeric products is discussed.

Some Aspects of Arcing in Incandescent Filament Lamps

The reduction of arcing failure in filament lamps by control of tungsten grain size, the composition and pressure of the gas filling, and suitable design of filament assembly is briefly described. A simple non-destructive method of measuring the arcing potential is suggested.

Reactions of methane, ethane, propane and n-butane on incandescent niobium filaments

The first page of this article is displayed as the abstract.

The Evaporation Rate of Filament Material from Alternating Current Heated Filaments

The operation of an incandescent filament on alternating current of the form, i = i0 sinωt, is reviewed. A model for the ac evaporation rate, in a vacuum of a uniformly heated straight wire, is presented in terms of: (1) The known temperature fluctuations, and (2) The evaporation rate evaluated at the do and the ac mean filament temperatures. It is shown that the ac evaporation rate can be significantly greater than the dc evaporation rate. A method of evaluating the ac evaporation rate in terms of the spectral modulation is developed.

The addition of atomic oxygen, obtained by the dissociation of molecules of oxygen on an incandescent iridium filament, to some solid olefins at low temperatures

1. The effective absorption of atomic oxygen, generated in the gas phase, by some solid olefins at low temperatures has been demonstrated. 2. Oxygen-containing compounds, formed as a result of the introduction of atoms of oxygen into the molecules of the original olefin, were detected among the reaction products.

Changes in the Dimensions of Incandescent Filament Lamps

The paper describes the changes in the dimensions of incandescent filament lamps for general lighting purposes which have occurred since their invention in 1878 as a result of various technical and commercial influences. The increasing importance of standardisation and of economy in manufacturing and distribution costs are noted.

Interaction of Hydrogen with Tungsten

Measurements have been made under ultra-high vacuum conditions of the rates and isotherms for the adsorption of hydrogen on tungsten, the rate of desorption of hydrogen from tungsten, and the rate of formation of atomic hydrogen by an incandescent tungsten filament. When hydrogen chemisorbs on tungsten at 77°, the sticking probability is 0.1 and two distinct states of binding, α and β, may be isolated at adsorption pressures as low as 2.5×10—9 mm. Analysis of desorption kinetics of the most tightly bound state, β, shows that hydrogen chemisorbs as atoms since evaporation is second order in adsorbed hydrogen. For nβ< 30×1012 molecules/cm2, vM=(5×10−3)n2exp(−31 000/RT) molecules/cm2-sec. At higher coverages, a decrease in heat of desorption is observed which is due to surface heterogeneity. At equilibrium, the amount adsorbed in the β state obeys a Temkin isotherm between 273° and 373°K; evaporation of hydrogen in the β state occurs down to temperatures as low as 77°K. Isosteric heats agree with heats derived from desorption measurements. The α state, populated before the β state is saturated at 77°K, is proportional to hydrogen pressure and probably consists of molecular hydrogen on top of the primary atomically chemisorbed layer. The rate of evaporation of atomic hydrogen when the filament temperature is raised above 1100°K is vA=(2.2×1013)n exp(−67 000/RT) molecules/cm2-sec. For pressures below 10—7 mm and filament temperatures above 1475°K, the fraction of molecules striking the filament surface that is dissociated is constant and at least 0.05. Values of surface coverage and the rate of formation of atomic hydrogen as a function of filament temperature and hydrogen pressure are derived from experimental data.

The adsorption of methane by barium films in the presence of a thermionic current

The adsorption of methane at pressures of 7×10 -7to 7×10 -6torr has been studied both in the presence and absence of a thermionic current drawn from a tungsten filament, using the capillary flow method of Wagener, and maintaining the pressure over the barium film constant. The pumping speeds of barium films covering up to 160 cm 2 and up to 20 mg in weight under normal conditions were very small and were less than 5 cc/sec at 1.5×10 -6 torr. The presence of an incandescent tungsten filament caused a slight increase in pumping speed of the barium films of about 10–20 cc/sec. Drawing an emission current from the filament appreciably increased the pumping speed of the getter, the increase amounting to 70–100 cc/sec at 1.5×10 -6 torr with a current of 5 mA. The pumping speed was independent of the area and weight of barium film but was approximately proportional to the thermionic current; it was almost independent of the pressure, up to 7×10 -6 torr, and hence the adsorption rate (pumping speed × pressure) was roughly proportional to pressure. The results show that the adsorption rate on barium films of methane activated by electron impact is determined entirely by the frequency of electron-gas molecule collisions. It is not known whether the active species consists entirely of ions or whether non-ionized radicals and molecules resulting from the decomposition of methane are involved.

Interaction of Atomic Hydrogen with Glass

An omegatron ion resonance mass spectrometer has been used to study residual gases in an ultra-high vacuum system. Atomic hydrogen, produced from molecular hydrogen by an incandescent tungsten filament, reacts with glass to produce contaminant molecules, CO, H2O, and CH4, whose presence seriously interferes with studies of surface phenomena. Such spurious effects are substantially reduced by substituting a lanthanum boride-coated tantalum filament for the tungsten electron source of an ionization gauge used to measure pressures of hydrogen. Quantitative measurements of the binding of atomic hydrogen by glass show the existence of two distinct binding sites of nearly equal population that are occupied simultaneously at low surface coverages and low temperatures. The rate of recombination of atomic hydrogen bound to glass is proportional to the number adsorbed and is much smaller than the rate of recombination of atomic hydrogen impinging on a glass surface from the vapor phase.

Interaction of Oxygen with Incandescent Filaments

With the aid of a mass spectrometer a study has been made of the gaseous contaminants present when oxygen is exposed to different incandescent filaments. In agreement with others CO and CO2 were the most abundant contaminants found. The amounts of CO and CO2 found, at a given filament temperature and oxygen pressure, were greater for Mo 0.031% C, W 0.012% C, and Re 0.010% C than for Ta 0.001% C. Also at the same oxygen pressure and filament temperature the quantity of CO found was much greater for a carbonized W filament than for any of the other filaments investigated. These results are consistent with the hypothesis that CO and CO2 are produced by the interaction of oxygen with the carbon present in the hot filaments. No evidence was found to indicate that the glass walls contribute to the formation of CO and CO2.

Recommended Practice for Reporting Photometric Performance of Incandescent Filament Lighting Units Used in Theatre and Television Production

Recommended Practice for Reporting Photometric Performance of Incandescent Filament Lighting Units Used in Theatre and Television Production

Lighting for the past 25 years and the future

IN 1955, the lighting industry celebrated Light's Diamond Jubilee commemorating the invention of the incandescent filament lamp and the birth of electric utilities in the form of Edison Electric Illuminating Companies. A feature of this celebration was a 75-kw incandescent lamp constructed especially for this use, just as a 50-kw lamp had been made for exhibit at the New York World's Fair in 1939. This mammoth lamp, burned from time to time for demonstration during the celebration, should not be taken to indicate that advance in lighting has been solely in the size of the source.

A filament noise source for 3 Gc/s

The construction of an incandescent filament lamp and suitable tuned waveguide mounting for use as a noise source at 3 Gc/s is described. Methods of measuring filament temperature are outlined and the procedure for assessing mounting losses is described. Also, results of some noise measurements on a 6-watt fluorescent lamp and some cold-cathode argon discharges are outlined.

Recommended Practice for Reporting Photometric Performance of Incandescent Filament Lighting Units: Used in Theatre and Television Production

Recommended Practice for Reporting Photometric Performance of Incandescent Filament Lighting Units: Used in Theatre and Television Production

Noise and Electron Temperatures of Some Cold Cathode Argon Discharges

Noise temperatures at 3000 Mc were compared with the corresponding electron temperatures for the positive columns of some cold cathode discharges in argon. The noise temperatures were measured using a superheterodyne receiver of low noise figure, by comparing the noise outputs of the various tubes with that from a commercial fluorescent lamp of measured noise output, a rapid comparison between known and unknown noise powers being effected by means of a hand-operated wave-guide switch. The noise temperature of the fluorescent lamp in its mounting was measured by comparison with an absolute standard consisting of an incandescent tungsten filament lamp fitted in a suitable wave-guide holder. Electron temperatures were measured by the Langmuir single-probe method. It is concluded that for most of the tubes measured, noise temperature, and electron temperature are in close agreement as required by the theories.

Cleanup of Atomic Hydrogen

When hydrogen is dissociated by an incandescent tungsten filament in a glass tube, some of it is cleaned up if the tube is cooled in liquid air. The amount cleaned up can be greatly increased by coating the inner wall with mercury or copper. In one experiment the amount cleaned up in cold mercury was equivalent to 14 monolayers of atomic hydrogen. The cleanup proceeded at a diminishing rate until the pressure fell to the value at which hydrogen left the mercury as fast as it entered. When hydrogen was cleaned up in a very thin coating of mercury there were 1.5 to 1.8 atoms of mercury per atom of hydrogen. All the cleaned-up gas was recovered when the tube was brought to room temperature. After cleanup in copper there was little recovery until the temperature rose above —150°K.

Modulation of Radiant Energy from Incandescent Filaments

The fluctuations in temperature of an ac-heated filament modulate the radiant energy produced. This paper considers the amplitude of the modulation as a function of temperature and wavelength of radiation. In a lamp heated with 60-cps power the modulation amplitude may become rather large (10% or more) as the wavelength of radiation decreases toward the ultraviolet region. Therefore, when an ac-heated lamp is used in photometric scanning procedures it is necessary to consider the modulation if transmission measurements are made. Some measurements of modulation amplitude vs wavelength are given for two types of 100-w tungsten-filament lamp heated with 60-cps power.The ratio of the modulation amplitude over the complete spectrum to that at a specific wavelength is proportional to the product of temperature and specific wavelength; hence a method of measuring temperature of an ac-heated filament is obtained.

The dehydrogenation of ethane at low pressure on incandescent platinum

Reactions of ethane on a platinum filament were examined at pressures of 10 -4 to 10 -7 mm and filament temperatures of 1300 to 1800°K. A mass spectrometric method was used whereby free radicals and atoms evaporating from the filament were directly observable. The activity of the filament depended upon its pre-treatment. A new filament, cleaned by flashing for only a short time, gave ethyl radicals and ethylene. With use the filament lost its activity. First, the formation of ethyl radicals ceased, and only ethylene was produced. With further use, this reaction ceased. No reaction at all was then observed. Progressive poisoning to ethane reaction also occurred when a filament was outgassed in vacuum. Residual oil vapours present at about 10 -9 mm pressure, were observed to react on the incandescent filament. A poisoned filament again converted ethane to ethylene in the presence of water or heavy water, but not in the presence of oxygen, hydrogen, oxygen + hydrogen mixtures or methyl alcohol. The probability of the reaction in the presep.ce of water was proportional to water pressure. No reaction of water was observed, and no isotope exchange between ethane and heavy water. The hypothesis is advanced that carbonization poisons the filament, and the adsorbed water on the carbonized filament facilitates the transfer of vibrational energy to adsorbed ethane. A poisoned filament could be made active again by heating in oxygen. The initial reaction of ethane was then again molecular dehydrogenation to ethylene, but ethyl radicals appeared after a short time. This is ascribed to reduction of an oxide layer. The probability of reaction of an ethane molecule per collision with the filament when ethyl radicals were formed was 10 3.5 exp (-40 kcal/ RT ). On a slightly used filament, giving ethylene only, it was 10 1.3 exp (-26.5 kcal/ RT ). Both reactions were first-order. Oxygen dissociated on a filament to give atomic oxygen in high yield. At extremely low pressures the order of reaction was one, but at higher pressures it changed towards one-half. The formation of atomic oxygen, and the ethane reactions, occurred quite independently when a mixture of the two gases was used. Dissociative adsorption to atoms is postulated for oxygen and molecular adsorption for ethane. The absolute rate of reaction for ethane is not in agreement with the concept of a transition state localized at a site on the surface. A mobile transition state is proposed. Other reactions which have been supposed to support the hypothesis of an immobile transition state are shown not to do so, but to support the concept of a mobile transition state.

Motion Picture Studio Lighting and Process Photography Report

THE BASIC COLOR sensitivity of the Technicolor process has been changed to a color temperature of 3350 K. When white light sources, such as sunlight, are used, the camera optical systems are filtered for proper balance. Incandescent tungsten filament lamps of the proper color temperatures are used unfiltered. When carbon arcs are used mixed with unfiltered tungsten lamps it becomes necessary to filter the carbon arcs to the lower color temperature. This is accomplished by using one MT-2 and one Y-1 filter on all high-intensity arc spotlamps and one MT-2 filter only on Duarc flood lamps. It is possible, however, to filter the camera optical train for sunlight balance and use the carbon-arc floodlamps unfiltered, the high-intensity carbon-arc spotlamps with only a Y-1 light yellow straw filter, and to filter the incandescent lamps with whiterlite filters as in the past. This gives the system a greater latitude so it may be used with incandescent tungsten lamps alone, where desired, at a key-light level as low as 150 ft-c; or with carbon arcs, or sunlight, with a key-light level of 300 ft-c; or with mixed lighting in either case provided the light sources are all adjusted to the balance of the particular camera filter system.