Measurement of Li target thickness in the EVEDA Li Test Loop

Abstract

A high-speed (nominal: 15m/s, range: 10–16m/s) liquid lithium wall jet is planned to serve as the target for two 40MeV and 125mA deuteron beams in the International Fusion Materials Irradiation Facility (IFMIF). The design requirement of target thickness stability is 25±1mm under a vacuum of 10−3Pa. This paper presents the results of the target thickness measurement conducted in the EVEDA Li Test Loop under a wide range of conditions including the IFMIF condition (target speed of 10, 15, and 20m/s; vacuum pressure of 10−3Pa; and Li temperature of 250°C). For measurement, we use a laser probe method that we developed in advance; this method generates statistical measurements method using a laser distance meter. The measurement results obtained under the IFMIF nominal condition (15m/s, 10−3Pa, 250°C) at the IFMIF beam center are as follows: average target thickness=26.08±0.09mm (2σ), mean wave amplitude=0.26±0.01mm (2σ), and maximum wave amplitude=1.46±0.25mm (2σ). Of the total wave components, 99.7% are within the design requirement. The analytically predicted target thickness is in excellent agreement with the experimental data, resulting in successful characterization of the Li target thickness.