Albert W. Hull

The Cause of High Voltage Surges in Rectifier Circuits

It is shown that high voltage surges are produced in apparatus associated with gas discharge devices when, and only when, the demand for current exceeds the current‐carrying capacity of the gas (or vapor). Cathode spot extinction and sputtering of hot cathodes cause only slight disturbances which do not produce high voltage in practical circuits. Experimental data on surge limits, i.e., the maximum currents that can be carried without surges, are given for four types of mercury vapor tube. These data lead to a single set of values of maximum current density as a function of vapor pressure, which may be used for the safe design of apparatus.

Glass‐to‐Metal Seals. II

This is a continuation of the work reported in 1934. The greater part of the paper is devoted to a discussion of the properties of iron‐nickel‐cobalt alloys, especially the composition Fe 54 percent, Ni 31 percent, Co 15 percent—called fernico—including sensitiveness to impurities and polymorphism. Three new glass‐metal combinations are described, the metals being 42 percent nickel‐iron, 26 percent chromium‐iron, and pure iron, respectively. The strength of the glass‐metal bond is discussed briefly.

A Basic Theory of the Mercury Cathode Spot

Most writers about the cathode spot have concluded that it is too complicated for valid conclusions. There is presented here a simple theory, which can be called basic, since it is founded on the single assumption that the electron emission is field emission.It follows immediately from this assumption that the positive ion current density must be about 5×105 A/cm2 to supply the necessary field of 2.7×107 V/cm; and this, with an allowance of 20 electrons per ion for the two‐stage ionization, determines an electron current density of 107 A/cm2.This large ion current and the resultant heating of the spot precludes an energy balance, which would require temperatures and pressures far above the critical to dissipate the heat by conduction and evaporation.Such a balance would never be reached, however, because of a mechanical balance between the forces of surface tension and vapor pressure, which limits the pressure and temperature to much lower values; namely a pressure of about 1 atm and the temperature of th...

The Phase of Arcback

Thyratrons of FG‐41 type were tested at over‐voltage for arcback in a circuit which simulates operating conditions very closely. Memory oscillograms showed the time in the cycle at which the arcbacks occurred. At a mercury‐control temperature of 45°C, the distribution was nearly random, with a maximum at the time of highest negative anode voltage, and depending on voltage in the same manner as the average arcback rate, taken over a long period. When the mercury‐control temperature was raised to 64°C, all the arcbacks occurred at the beginning of negative voltage application. These results are interpreted on the theory recently advanced by Kingdon and Lawton, which attributes arcback to charging up of small non‐conducting particles on the surface of the anode. At low vapor pressure, where the ions remaining from the discharge have time to diffuse to the electrodes before negative voltage is applied, the charging is produced by processes such as glow discharge and field emission, which depend on voltage; he...

Stresses in Cylindrical Glass‐Metal Seals with Glass Inside

It was shown previously that, when a cylinder of glass is sealed to the outside of a metal rod, the principal stresses in the glass are of opposite sign, so that tensile stresses cannot be avoided except by a perfect match. In this article the stresses are calculated for a solid glass cylinder sealed to the inside of a metal cylinder. It is shown that the stresses are all of the same sign, so that a moderate mismatch in thermal expansion, with the metal expansion the greater, is allowable and perhaps desirable. Large differences in expansion should be avoided, because of the shearing stresses at the ends.

Characteristics and Functions of Thyratrons

The Thyratron is a tube of very low resistance (arc discharge) which can be started or prevented from starting by a grid. Its qualities are: enormous power‐amplification, approximately 1011 per tube; efficiency between 95 and 99 percent at all voltages above 250; unlimited size, as regards current‐capacity; high‐voltage limit equal to that of the Pliotron; starting time one to six microseconds; deionization time 10 to 500 microseconds.Use of Thyratron as switch and for power control. The controlling element may be a switch, clock, thermostat, or photo‐tube; the controlled element a motor, magnet, contactor, or reactor. Typical applications of this kind of use are; turning on lamps at dusk, dispatching products to predetermined stations, cutting hot steel bars to exact length, opening doors at the approach of a person, wrapping packages, sorting beans and other articles, counting people or products, operating line or spot welding machines. By varying the phase of the grid‐voltage with respect to that of th...

Fundamental processes in gaseous tube rectifiers

The theory involved in the phenomena occurring in gas-filled rectifier tubes is discussed here. It is shown how the two basic laws of electronics, the Richardson-Laue-Dushman equation of thermionic emission and the Child-Langmuir space-charge law, affect the behavior of these tubes.

Abridgment of gas-filled thermionic tubes

This paper describes a fundamental principle of thermionic gas tube operation, by which cathode disintegration may be entirely avoided; and a new type of cathode which requires much less heat energy than any hitherto used. With these improvements hot cathode gas tubes appear to be practical, and their fundamental characteristics as lamps, rectifiers, and “thyratrons” are briefly described.

The Axially Controlled Magnetron A New Type of Magnetron, Controlled by Current Through the Filament

In vacuum tubes with straight filaments of large diameter, it is found that the magnetic field of the heating current exercises a restraining effect on the escape of electrons, equivalent to the action of the grid in the pliotron, or the impressed magnetic field in the magnetron. This new valve principle may be utilized to control the output of the tube for practical purposes, such as changing high-voltage direct current into alternating current; and leads to a very simple and efficient type of tube.

Fundamental Electrical Properties or Mercury Vapor and Monatomic Gases

Electrical properties of mercury vapor and monatomic gases are discussed from a theoretical standpoint in this article. In the first part of the article, the author discusses briefly the elementary processes of excitation and ionization of atoms upon which the electrical properties of gases depend. With this insight into the fundamental processes as a background, the author discusses in Part II the electrical conductivity of gases under various conditions. This is the eleventh in a series of special articles prepared under sponsorship of the A.I.E.E. committee on education.