Validation of liquid lithium target stability for an intense neutron source

Abstract

This paper reports on validation results for the stability of a liquid lithium (Li) target intended for use as an intense fusion neutron source such as for the International Fusion Materials Irradiation Facility (IFMIF), an advanced fusion neutron source (A-FNS), and a demonstration fusion power plant (DEMO)-oriented neutron source (DONES). The variation in the thickness of a Li target must be suppressed to within ±1 mm inside a deuteron beam footprint to both maintain the integrity of the Li target and guarantee the desired level of neutron flux. We achieved a stable Li target with an average thickness variation of just 0.17 mm inside the beam footprint under standard IFMIF operating conditions (target speed: 15 m s−1; vacuum pressure: 10−3 Pa; and Li temperature: 250 °C). Moreover, the mean and maximum wave amplitudes at the beam center under such conditions were found to be 0.26 mm and 1.46 mm, respectively; these are small enough to satisfy operational requirements. Finally, it was determined that the stability of the Li target remained unchanged despite using it for an extended period of 1561 h. This finding is regarded as a significant step toward the realization of the IFMIF and the potential use of relevant neutron sources such as A-FNS and DONES.