Study on heat transfer between the High-Luminosity LHC beam screens and the He II-cooled beam tube

The new beam screens for the inner triplets in the HL-LHC are designed to intercept heat loads of up to 25 Wm$^{-1}$ between 60 K and 80 K. The screens need to be mechanically supported by the beam tube at 1.9 K while limiting heat transfer to the same tube to less than 0.5 W m$^{-1}$. Measurements for the thermal validation of the beam screens were carried out on a dedicated test stand at the Central Cryogenic Laboratory at CERN. This paper describes the first measurement campaign of a full-scale D1-type beam screen mock-up: several parameters such as base temperature and heating power were varied, and results include heat transfer mechanisms within the beam screen and more importantly to the 1.9 K beam tube that forms the physical boundary between beam screen and He II-cooled magnets.