Influence of a wick lining on the evaporation rate of lithium from a charge exchange canal

Abstract

A wick lining is used with a lithium charge exchange canal for reducing the consumption of lithium. The wick helps to condense the lithium vapour more effectively and to make it flow back to the main oven. For its efficient functioning, the temperature gradient along the wick has to be properly maintained. The present studies were carried out to assess the extent of reduction in lithium loss when using the wick and to determine the optimum temperature settings. The evaporation rate of lithium vapour from a charge exchange canal (General Ionex Model-712) has been investigated in the temperature range from 470 to 575° C. The measurements were carried out with and without a stainless steel wire mesh wick lining, inside the canal. A quartz crystal oscillator type rate meter was used for monitoring the evaporation rate. The results indicate that, when the wick lining is inserted, the reduction in evaporation rate of lithium is only 20%. This differs much from the result of Greenway [Report 85/11, Oxford University, Nuclear Physics Laboratory (1985)] who reported a reduction by a factor of 8. The evaporation rate is also found to depend on the canal end heater temperature, maintained high enough to keep the condensing vapour in liquid state. The optimum temperature settings for the end heaters have been found to be 300 ° C. The experimental arrangements and results are presented in this paper.