DC Input Power Research Articles

Effects of Argon Atoms on the Self-Absorption and the Intensity of Hg 2537-Å Radiation in Hg + Ar Discharges

A study was made of the feasibility of increasing the efficiency of fluorescent lamps at high powers by increasing the Hg 2537-A resonance radiation through a reduction of self-absorption. Specifically, we attempted to reduce the Hg 2537-A self-absorption by introducing a higher pressure of a foreign gas (argon) to alter the Hg 2537-A absorption line shape and width by collision broadening. The intensity of the Hg 2537-A line in Hg + Ar discharges was measured as an independent function of mercury pressure (0.7 mTorr to 27 mTorr), argon pressure (5 Torr to 400 Torr), and dc input power (5.5 W to 97 W). A detailed theoretical analysis indicates that there are four ways that additional argon reduces the Hg 2537-A self-absorption: (1) The Hg 2537-A line gets broader simply because the additional argon atoms increase the Hg-Ar collision frequency; (2) adding argon causes the gas temperature to rise and this drives the Hg-Ar collision frequency still higher; (3) the rise in gas temperature also causes an increase in the Hg 2537-A doppler width; (4) the additional argon changes the Hg 2537-A line shape from doppler dominated to a collision dominated profile. The experiments demonstrate, however, that no gain is achieved in the Hg 2537-A intensity with the addition of extra argon in spite of the beneficial effect on the self-absorption escape rate. This advantage is apparently offset by the argon's reduction of the electron energy which leads to fewer mercury atoms excited to the Hg 6(3)P(1) state.

Sputtering of insulators in an RF discharge

This paper describes a technique for depositing insulating layers, onto suitable substrates, by the mechanism of sputtering in a radio-frequency excited discharge. The sputtering equipment and vacuum system have been designed so that facilities were available for the direct comparison of three different methods of sustaining a glow discharge at low pressures: 1. 1 By using a two-electrode Penning system (Diode); 2. 2 By means of a hot cathode discharge (Triode); 3. 3 By means of a second RF coil coupling inductively directly into the gas (Double RF) Deposition rates of a barium-alumino silicate glass, as a function of dc power input for the three methods of sputtering mentioned, are given. It is shown that high rates of deposition can be achieved using the double-RF system, i.e. rates in the region of 6.6 × 10 −10 m.S −1 (400Å/min) have been obtained for a dc power input of approximately 800 watts. Deposition rates were also investigated over a range of Argon/oxygen mixtures. A detailed examination of the electrical properties of sputtered barium-alumino-silicate glass thin film capacitors has been made by sandwiching the dielectric layers between vacuum-deposited aluminium electrodes. Measurements of permittivity (6.15-6.4), tan δ (0.0017), dielectric strength (3×10 6 V.cm −1), resistivity (≈10 15ωcm), and temperature coefficients of capacitance (120 ppm/°C over the ranges 25°–150°C and 100 Hz-100kHz) were found to compare closely with that of the bulk material.

A New RF-dc Substitution Calorimeter with Automatically Controlled Reference Power

A new dual-dry-load calorimeter, incorporating automatically controlled reference dc input power, has been developed at the National Bureau of Standards. The calorimeter will be used as a reference standard at frequencies from dc to 4.0 GHz in the power range of 10 mW to 1 watt. The maxmum measurement uncertainty is 0.26 percent at frequencies below 1 GHz and 0.35 percent at frequencies above 1 GHz. The time required for the measurement system to reach equilibrium is less than two minutes. Construction details and design of the calorimetric and feedback control system are given, along with an error analysis and results of intercomparisons with other standards.