Dynamic simulations and transient management 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 have to be used to help 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.