Design and measurement methods for a lithium vapor box similarity experiment

TL;DR

This paper presents the design and measurement techniques for a lithium vapor box experiment aimed at validating models for plasma detachment and heat redistribution in fusion divertor concepts.

Contribution

It introduces a novel experimental setup and measurement methods for studying lithium vapor behavior relevant to fusion divertor applications.

Findings

Design of a lithium vapor box apparatus with temperature control

Measurement of mass flow and temperature with high precision

Validation of a DSMC model for lithium vapor flow

Abstract

The lithium vapor box divertor is a concept for handling the extreme divertor heat fluxes in magnetic fusion devices. In a baffled slot divertor, plasma interacts with a dense cloud of Li vapor which radiates and cools the plasma, leading to recombination and detachment. Before testing on a tokamak the concept should be validated: we plan to study detachment and heat redistribution by a Li vapor cloud in laboratory experiments. Mass changes and temperatures are measured to validate a Direct Simulation Monte Carlo model of neutral Li. The initial experiment involves a 5 cm diameter steel box containing 10 g of Li held at 650 degrees C as vapor flows out a wide nozzle into a similarly-sized box at a lower temperature. Diagnosis is made challenging by the required material compatibility with lithium vapor. Vapor pressure a steep function of temperature, so to validate mass flow models to within 10%, absolute temperature to within 4.5 K is required. The apparatus is designed to be used with an analytical balance to determine mass transport. Details of the apparatus and methods of temperature and mass flow measurements are presented.