Wayne B. Nottingham

Electrical and Luminescent Properties of Willemite Under Electron Bombardment

An insulated surface uniformly bombarded with electrons of a given energy attains a potential relative to other elements in a high vacuum tube such that exactly as many electrons leave the surface by secondary emission as there are primary electrons arriving. A tube and circuit have been constructed for determining accurately this potential for willemite surfaces while being bombarded by electrons of energy range up to 10,000 volts. It was found that the surface potential was only slightly negative with respect to the most positive anode of the tube over the lower range of energy but finally reached an upper limit of potential relative to the cathode usually between 6000 and 7000 volts. The resistance between wires covered by the willemite was found to be independent of the bombarding current and voltage except in so far as this bombardment changed the temperature of the material. A special potassium phototube is described which was used to determine the light output from the bombarded surface as a functi...

Thermionic Diode as a Heat‐to‐Electrical‐Power Transducer

The high‐vacuum thermionic diode is shown to be capable of converting heat to electric power. For this purpose, a low work‐function collector, a small spacing, and sufficient temperature difference between the emitter and the collector are necessary. A detailed understanding of both thermionic emission and space‐charge phenomena are needed for evaluating the effectiveness of this transducer. With VR defined as the critical bias potential that gives zero potential gradient at the collector, the maximum available power is given by the relation 3.7×10−6 VT½(VR2/w2) watts/m2. Here, VT is the voltage equivalent of the temperature T/11 600. In the range of emitter temperature from 1200°K to 1700°K, the most optimistic conversion efficiency lies between 3 and 4% for a diode of 0.001‐inch spacing. With a suitable choice of emitter inhomogeneity, the introduction of cesium vapor should improve the efficiency of this device.

Half‐Cycle Spot‐Welder Control

A circuit for controlling a small spot‐welder is described which utilizes simple, inexpensive, cold cathode tubes. Variation of the welding heat is accomplished by control of the fraction of a single half‐cycle during which current is supplied to the welder transformer. Increased pressure is found to be necessary for satisfactory welding.

A Survey of Present Methods Used to Determine the Optical Properties of Phosphors

A brief review of the theory of phosphors is given in terms of the electron-band picture of impurity semiconductors in order to show the reasons for researches designed to obtain the optical properties of phosphors. The automatic spectroradiometer is described since it is an instrument which yields so much information of value in phosphor research, development, and quality control. Some problems of spectroradiometer standardization are discussed in some detail, since the data obtained cannot be correctly interpreted by the I.C.I. system of color specification and interpretation unless satisfactory standards are maintained and used. A brief discussion is given of the application of the I.C.I. system to help in the choice of phosphors required to produce a suitable “white” for television cathode-ray tubes. Other researches discussed include the determination of phosphor excitation curves, the emission of light as a function of temperature and of time, and the correlation of spectral excitation and absorption data.