Control of the heavy-ion beam line gas pressure and density in the HYLIFE thick-liquid chamber

Abstract

Controlling the density and pressure of the background gas in the beam lines of thick-liquid heavy-ion fusion chambers is of paramount importance for the beams to focus and propagate properly. Additionally, transport and deposition of debris material onto metal beam-tube surfaces may reduce the breakdown voltage and permit arcing with the beam. The strategy to control the gas pressure and the rate of debris deposition is twofold. First, the cool thick-liquid jet structures will mitigate the venting to the beam tubes. The ablation and venting of debris through thick-liquid structures must be modelled to predict the quantities of debris reaching the beam ports. TSUNAMI calculations have been performed to estimate the mass and energy flux histories at the entrance of the beam ports in a 9×9 HYLIFE pocket geometry. Secondly, additional renewable shielding will be interposed in the beam tubes themselves. Thick-liquid vortexes are planned to coat the inside of the beam tubes and provide a quasi-continuous protection of the beam-tube walls up to the final focus magnets. A three-component molten salt, flinabe, with a low melting temperature and vapor pressure, has been identified as a candidate liquid for the vortexes. The use of flinabe may actually eliminate the necessity of mechanical shutters to rapidly close the beam tubes after target ignition.