• M. Sitko, B. Skoczen
  CUT, Krakow

The array of cor­rec­tor mag­nets in the LHC is pow­ered by means of a su­per­con­duct­ing line at­tached to the main mag­nets. The sub­cool­ing time of the line has to be min­i­mized in order not to delay the op­er­a­tion of the col­lid­er. The cor­re­spond­ing ca­ble-in-con­duit prob­lem is for­mu­lat­ed in the frame­work of two-flu­id model and the Gorter-Mellink law of heat trans­port in su­per­flu­id he­li­um. A model of λ front prop­a­ga­tion along the nar­row chan­nel con­tain­ing su­per­con­duc­tors and liq­uid he­li­um is pre­sent­ed. The one-di­men­sion­al model* adopts plane wave equa­tions to de­scribe λ front prop­a­ga­tion. This ap­proach to nor­mal-to-su­per­flu­id phase tran­si­tion in liq­uid he­li­um al­lows to cal­cu­late the time of sub­cool­ing and the tem­per­a­ture pro­file on ei­ther side of the trav­el­ling front in long chan­nels con­tain­ing su­per­con­duct­ing bus-bars. The model has been ver­i­fied by com­par­ing the an­a­lyt­i­cal so­lu­tions with the ex­per­i­men­tal re­sults ob­tained in the LHC String 2 ex­per­i­ment. The pro­cess of the LHC Dis­per­sion Sup­pres­sors sub­cool­ing has been op­ti­mized by using the pre­sent­ed model. Based on the re­sults, a novel con­cept of cop­per heat ex­chang­er for LHC DS op­er­at­ing in su­per­flu­id he­li­um is in­tro­duced.

* M. Sitko, B. Skoczeń, Modelling HeI-HeII phase transformation in long channels containing superconductors, Int. Journal of Heat and Mass Transfer, Vol. 52, Issues 1-2,pp. 9-16, 2009.