High Frequency Electric Field Research Articles

On an Observation Method by Visual Power of High Frequency Electric Field

On an Observation Method by Visual Power of High Frequency Electric Field

Osmosis in a High Frequency Electric Field

Osmosis in a High Frequency Electric Field

The initiation of breakdown in gases subject to high frequency electric fields

This paper discusses the literature dealing with the experimental data on the onset of electrical breakdown in gases covering the range from power frequencies to 9,000 Mc/s. As the applied frequency is increased, various phenomena affect the circumstances of breakdown, particularly the stress at which this occurs. These phenomena begin at moderate radio frequencies, for gaps of the order 1 cm., with the non-removal of positive ions from the gap, and continue at much higher frequencies with the non-removal of electrons from the gap. Each of these effects, especially the persistence of electrons, lowers the breakdown voltage. The detailed shape of the curve relating breakdown voltage with pd, where p is the gas pressure and d the gap length, is much affected by the design of the electrode system and of the containing vessel. Extensive results are available on hydrogen. Microwave breakdown has been studied in waveguides and in resonators : a considerable amount of theoretical work has been published based chiefly on the study of the balance between the growth of ionization by collision processes and the removal of electrons to the boundaries by diffusion. This work shows agreement with experiment for hydrogen over a wide range of frequencies and pressures, and for the monatomic gases where suitable data are available. Information on microwave breakdown at high values of pd is very limited: the breakdown is very abrupt and presents features not readily explained in terms of the diffusion theory.

Development of the Low Pressure Electrodeless Discharge in a High-Frequency Electric Field

Development of the Low Pressure Electrodeless Discharge in a High-Frequency Electric Field

Conductivity at Microwave Frequencies

If a high frequency electric field is applied to an ionized gas, the resulting oscillatory motion of the free electrons will give rise to an alternating current.

On Hascgawa's Phenomena in the High-frequency Electric Field

On Hascgawa's Phenomena in the High-frequency Electric Field

On a New Observation Method of High Frequency Electric Field (I)

On a New Observation Method of High Frequency Electric Field (I)

Starting potentials of electrodeless discharges

In a previous paper the starting process of electrodeless discharges in high frequency electric fields at very low pressure was shown to be controlled by the emission of secondary electrons released by oscillating electrons which hit the walls with sufficient speed. This explained why the starting field strength was found to be independent of the nature of the gas and to rise suddenly to infinity when the wave-length exceeds a critical value—the cut-off—which depends on the size of the vessel and the substance of its inner surface. This paper records measurements of the starting field which have been carried out at pressures between about 0·2 and 350 mm. Hg in hydrogen, nitrogen, neon and some in deuterium and helium covering a range of wave-lengths between 5 and 2000 m. in vessels of different sizes and types of glass. The results show that with increase in pressure the nature of the gas becomes of importance. In the above-mentioned gases the starting field rises slowly and continuously with the wave-length up to a region where a kind of cut-off occurs which is due to the growing amplitude of electron oscillation and the corresponding rise of wall losses. In nitrogen and hydrogen and deuterium sharp cut-offs persist up to the highest pressure used. In the rare gases these discontinuities occur only below about 0.2 mm. Hg in Ne and 0.5 mm. Hg in He, while at larger pressure the cut-off extends over a considerable range of wave-lengths. The different behaviour of molecular and rare gases seems to be caused by narrow and wide electron energy distributions respectively. The cut-off occurs when the amplitude of oscillation of the electrons becomes equal to the length of the tube. From values of the cut-off and the associated fields the electron drift velocity has been derived. The results are in general accord with the known data which are only available for small fields. Above the cut-off a strong field is necessary to start a discharge in hydrogen and nitrogen. In hydrogen the starting field decreases with increasing wavelength and it is shown that this decrease is due to positive molecular ions producing electrons probably by impinging on the walls. In nitrogen the picture is more complex. In deuterium the positive molecular ion is effective; its mobility is found to be about one-half of that of hydrogen. In neon at higher pressures and at wave-lengths below 100 m. the starting field rises with decreasing wave-length; this is because the electrons collide too seldom with gas atoms to attain final random velocity. The only gas investigated at pressures comparable to one atmosphere was neon. Even at these pressures a kind of cut-off occurs. At one atmosphere the starting field is about 500 V/cm., by extrapolation it would be 15,000 V/cm. in hydrogen and of the order of 2000 V/cm. in helium for wave-lengths below the cut-off.

The Breakdown of Gases in High Frequency Electrical Fields

A theory is proposed to explain the mechanism of breakdown of gases in high frequency electrical fields. It is assumed that breakdown occurs when the electrical field and the frequency are such that an electron acquires the ionizing energy at the end of one mean free path. The field for breakdown is thus a function of the frequency of the applied potential and the ionization potential and pressure of the gas. The fields for breakdown of argon and xenon are calculated and expressed as functions of the frequency and the gas pressure. The calculated potentials are compared with experimental data, and good agreement is found for frequencies greater than ${10\ifmmode\times\else\texttimes\fi{}10}^{6}$ c.p.s.

Discussion: “Temperature Distribution in White-Oak Laminated Timbers Heated in a High-Frequency Electric Field” (Dunlap, M. E., and Bell, E. R., 1947, Trans. ASME, 69, pp. 509–517)

Discussion: “Temperature Distribution in White-Oak Laminated Timbers Heated in a High-Frequency Electric Field” (Dunlap, M. E., and Bell, E. R., 1947, Trans. ASME, 69, pp. 509–517)

Discussion: “Temperature Distribution in White-Oak Laminated Timbers Heated in a High-Frequency Electric Field” (Dunlap, M. E., and Bell, E. R., 1947, Trans. ASME, 69, pp. 509–517)

Discussion: “Temperature Distribution in White-Oak Laminated Timbers Heated in a High-Frequency Electric Field” (Dunlap, M. E., and Bell, E. R., 1947, Trans. ASME, 69, pp. 509–517)

Temperature Distribution in White-Oak Laminated Timbers Heated in a High-Frequency Electric Field

Abstract High-frequency dielectric heating has been applied to the process of laminating commercial white-oak ship timbers. Specimens 6 × 6 × 24 in., composed of eight laminations ¾ × 6 × 24 in., were heated both with and without glue to study the temperatures obtaining in the glue-line areas. The uniformity of temperatures depends upon the density, moisture content, and arrangement of the laminations, direction of the electric field, and thermal insulation of the heated material. The effect of these variables is greater when the electric field and glue lines are parallel than when they are mutually perpendicular. Thermocouples were used for rapid temperature measurement. A method of heating the sides of timbers effectively was developed.

Discussion: “Temperature Distribution in White-Oak Laminated Timbers Heated in a High-Frequency Electric Field” (Dunlap, M. E., and Bell, E. R., 1947, Trans. ASME, 69, pp. 509–517)

Discussion: “Temperature Distribution in White-Oak Laminated Timbers Heated in a High-Frequency Electric Field” (Dunlap, M. E., and Bell, E. R., 1947, Trans. ASME, 69, pp. 509–517)

Closure to “Discussions of ‘Temperature Distribution in White-Oak Laminated Timbers Heated in a High-Frequency Electric Field’” (1947, Trans. ASME, 69, pp. 517–518)

Closure to “Discussions of ‘Temperature Distribution in White-Oak Laminated Timbers Heated in a High-Frequency Electric Field’” (1947, Trans. ASME, 69, pp. 517–518)

High-Frequency Electric Fields as Lethal Agents for Insects1

High-Frequency Electric Fields as Lethal Agents for Insects1

Electromagnetic Field Inside a Cylinder with a Gap

Complete equations below the lowest cut-off frequency of transverse magnetic type relating the high frequency electric field and magnetic field inside a metallic cylinder excited through a gap and an assumed field at the gap are developed. Curves are calculated based on the equations which can be used to estimate the relative field strength at different points inside the cylinder. Equivalent capacitance due to the energy storage in the cylinder can be calculated and used for estimating the resonant frequency of the associated cavity. The equations can be degenerated to an electrostatic form and used for electron optical calculations.

XLIII. Two methods of measuring ultra high frequency electric fields

1. Summary Two methods are described which were developed, in connection with work on high frequency discharges in gases, for the measurement or comparison of electric field strengths of the order of 10 volts/cm, at frequencies up to 500 Mc/s.

An Instrument for Measuring Electrical Field Strength in Strong High Frequency Fields

An instrument is described which measures the intensity of the high frequency electric field, point by point, by means of the electrodeless discharge and a photoelectric device. The instrument is applicable to dosimetry and for local measurements in short wave therapy, but can also find application for investigation on insulators and other parts exposed to high voltage. The operation of the instrument and some examples of results obtained with the instrument are stated.

Experiments with Colpidium campylum in High-Frequency Electric and Magnetic Fields

Experiments with Colpidium campylum in High-Frequency Electric and Magnetic Fields

On the Temperature Rise of Insulating Materials in the High-Frequency Electric Field

On the Temperature Rise of Insulating Materials in the High-Frequency Electric Field