Dynamic simulations of the HL-LHC cryogenic system during beam operation

This paper presents a set of dynamic simulations performed on the future High Luminosity Large Hadron Collider (HL-LHC) cryogenic system. The objectives of these simulations are to provide main pressure, temperature and flow transients over the cryogenic distribution system around the collision points 1 and 5 during the forecast beam operation. These simulations serve the different cryogenic system specifications where strong dynamic heat loads will induce significant transient modes. This dynamic model embeds the 1.9 K cooling loops (inner triplets, D1 -D2 magnets and crab cavities), the beam screen cooling loops between 60 K and 80 K or between 4.5 K and 20 K and the cryogenic distribution line. As result, a series of recommendations is given to mitigate sufficiently the transients such as the use of significant preloading of magnets in association with feed-forward controls.