Kevin G. Rhoads

A high-accuracy, calibration-free technique for measuring the electrical conductivity of liquids

A high-accuracy, calibration-free technique to measure the electrical conductivity of liquids has been developed — the coaxial cylinders technique. Because the liquid under investigation comes in contact only with metal and not with anything dielectric, this technique enables the measurement of the electrical properties of liquids inaccessible by classical high-accuracy techniques. Two coaxial cylindrical electrodes are immersed in the liquid to an arbitrary initial depth, and ac impedance is measured over a wide range of frequency. This process is repeated at many immersions. The electrical conductivity is calculated from the change in measured conductance with immersion. This technique was validated in 1.0, 0.1, and 0.01 D KCl(aq) solutions at room temperature. Measured electrical conductivities were within ±0.5% of the standard reference values.

Electro-Optic Charge Injection and Tramsport Measurements in Highly Purified Water and Water/Ethylene Glycol Mixtures

Extensive Kerr electro-optic field mapping and voltage/ current measurements have been taken with highly purified water over the temperature range of T= 0 to 30°C using parallel plane electrodes with average field strengths up to 160 kV/cm. The Kerr constant of water B was measured to be B ¿, 3.4 to 3.6x1O-14 M/V2 for free-space light wavelength 590 nm and varies only slightly with temperature over the measurement range. Photomultiplier tube measurements at 633 nm at ¿10°C found water to have a Kerr constant B ¿ 2.7 to 2.9x10-14 m/V2 while ethylene glycol had a negative Kerr constant B ¿ -(.8 to .9)x1O-14 m/V2. Water/ethylene glycol mixtures had an essentially linear variation of Kerr constant between these limits as a function of weight fractions, having a zero Kerr constant at about 79% glycol/21% water by weight . With pure water, a HV step has no volume charge at t=0. For times greater than 500 ¿s, stainless steel and copper electrodes generally inject positive charge although under some conditions with mixed electrodes they injected negative charge, aluminum electrodes only inject negative charge, while brass electrodes can inject either positive or negative charge. Thus, by appropriate choice of electrode material combinations and voltage polarity, it is possible to have uncharged water, unipolar charged negative or positive, or bipolar charged water. Generally, the bipolar case allows a higher applied voltage without breakdown, presumably due to the lower electric field strengths at the electrodes due to the space charge shielding.

Transference number measurements of TiO2–BaO melts by stepped-potential chronoamperometry

TiO2–BaO melts have been under investigation as candidate electrolytes for the electrolytic production of titanium. Transference number measurements have been made by stepped-potential chronoamperometry at two compositions: 67 mol% TiO2 (1328<T<1487°C) and 73 mol% TiO2 (1210<T<1477°C). A theoretical analysis of the technique, capable of distinguishing between variations in ion density and variations in net free-charge density, is presented.

Relative Dielectric Constant Measurements in the Butyronitrile‐Chloroethane System at Subambient Temperatures

By means of electrochemical impedance spectroscopy, the relative dielectric constant was measured as a function of composition and temperature in the butyronitrile-chloroethane system from -35 to -105°C. A customized cell was designed by iterative optimization; the equivalent circuit was used to assess the impacts of the electrical properties of the sample, the limitations of the instrumentation, and the data reduction technique. To account for strong local ordering effects due to molecular association in these solutions, a new model, termed extended Kirkwood-Onsager (EKO), was developed. For solutions rich in chloroethane, structural features are inferred with this model.

Improved cooling on the Varian E220/E500 series implanters

Single wafer ion implanter manufacturers have traditionally relied on gas-cooled mechanical clamps for higher beam power applications and non gas-cooled electrostatic clamps (ESC) for lower power applications. Varian has recently developed a mid-power, non-gas-cooled ESC. This improvement allows for higher wafer throughput than a traditional ESC without the complexity of gas cooling.

Effects of electrode material on charge injection, transport, energy storage and dissipation in highly purified water

Extensive Kerr electro-optic field mapping and voltage/current measurements have been taken with highly purified water over the temperature range of T=0–30°C using parallel plane electrodes with average field strengths up to 160kV/cm. The Kerr constant of water B was measured to be B≃3.4–3.6×10−14m/V2 for free space light wavelength of 590nm and only slightly varies with temperature over the measurement range. For a step high voltage, there is no volume space charge at t=0+. For times greater than 500µs, stainless steel and copper electrodes generally inject positive charge, although under some conditions with mixed electrodes they injected negative charge; aluminum electrodes only inject negative charge; while brass electrodes can inject either positive or negative charge. Thus, by appropriate choice of electrode material combinations and voltage polarity, it is possible to have uncharged water, unipolar charged negative or positive, or bipolar charged water. Generally, the bipolar case allows a higher applied voltage without breakdown, presumably due to the lower electric field strengths at the electrodes due to the space charge shielding. Although injected space charge increases the stared electric energy over the capacitive space charge free energy, (1/2)Cv2, for ohmic conduction the energy delivered to a resistive load is reduced because of internal dissipation in the capacitor. Volume space charge makes no contribution to the load energy but increases the dissipation in the capacitor.