Current Sweep Rate Research Articles

Instability of persistent current switch

The instability for a persistent current switch (PCS) wound bifilarly by a CuNi matrix conductor was studied experimentally and by numerical calculations. The temperature rise due to self-field AC loss during the ramping up of the current causes degradations. The quench current gradually decreases to the adiabatic value, if the current sweep rate is progressively increased. Current transfer from the current terminal to the winding limits the current capacity for the PCS wound by a thick conductor, such as 0.9 mm in diameter. A short ramp pulse causes premature quenches at extremely low currents, which may be due to heat concentration of the self-field AC loss in the conductor outer shell.

アルミニウムの交流エッチングにおけるポーラス層の生成におよぼす諸因子の影響

The effect of such variables as etchant concentration, bath temperature, current density and current sweep rate on the cubic pit propagation and porous etch structure formation is discussed by means of electron microscopy and galvanovoltammetry. Maximum values of electrostatic capacitance were obtained under conditions for the formation of a deep porous etched layer. The formation of such a layer was found to be due to the formation and breakdown of a thin anodic film covering the inner surface of the cubic pits during etching. As indicated by the shape of cyclic polarization curves, the breakdown of the anodic film was facilitated by increases in the concentration and temperature of the etching solution, and suppressed by increases in the current sweep rate. This is explained by the rate at which Cl- ions are supplied to the bottoms of cubic etch pits.

永久電流スイッチの不安定性原因

Persistent Current Switch (PCS) is one of the important part of persistent current mode magnet system. The PCS has some degradation: it quenches at far below the critical current. Magnet system is restricted by the PCS quench. This paper studies the characteristics of PCS wound by a thinner CuNi matrix conductor such as 0.3mm in diameter for various magnetic field. It is obtained that its quench currents decrease with current sweep rate. In order to explain this dependence of current sweep rate, following instability model is developed: self-field AC losses increase PCS winding temperature thus PCS is quenched when current reaches its critical current determined by PCS's temperature. Numerical calculation on the model was performed and its result agreed with the experiment data.

The potentiodyanmic formation and reduction of a silver sulfide monolayer on a silver electrode in aqueous sulfide solutions

A potentiodynamic study of silver electrodes in aqueous sulfide solutions, carried out to form phase silver sulfide films, revealed that a monolayer of silver sulfice forms as a distinct and separate stage of film growth at an underpotential of about 0.12 V. The monolayer peak (and its cathodic counterpart) was also characterized by a linear relationship between peak current density and potential sweep rate and a constant charge density of about 0.2 mC/cm 2. The potentiodynamic E/ i curves for the silver sulfide monolayer were simulated by computer on the basis of a mechanism of the initial adsorption of HS − on the silver surface in a fast equilibrium step followed by a rate determining electron transfer step to form AgHS as a surface intermediate. The AgHS species then rapidly diffuses on the surface and joins a growing two-dimensional silver sulfide monolayer nucleus. Under the experimental conditons studied here, the formation and reduction of the silver sulfide monolayer was found to be of intermediate kinetic reversibility.