**** Cryogenics for Superconducting Links: 6th HiLumi Meeting Update **

1. Cryogenics for sc links, a short update S. Claudet, CERN-TE-CRG 6th HiLumi annual meeting, Paris 14-16 Nov 2016

2. Content • Recall basic cooling principles & schemes • Various types of sc-links and cooling • Summary Cryogenics for sc links, short update

3. Where do we stand • Specific cooling schemes mostly extracted from MS57 reference document integrated in HILUMILHC-Del-D6-2-V0 • No new work done on cooling principles since sc-links integration in underground areas • Only minor contributions mostly for alternatives around Q4-Q5-Q6 with the aim to re-use existing DFBL’s Cryogenics for sc links, short update

4. Baseline as presented in “HILUMILHC-Del-D6-2-V0” ? Schematic & work by Udo Wagner, 2014 Any special requirement for operating modes ? - Cool-down: conductor cooling 1st, then shield, or tentatively all at the same time, or … ? - 20K or 80K shield (stand-by?) Scheme for LTC secondary link (baseline) NEW, To ensure correct cooling of LTC link in case of perturbation of Line_C temperature Some of the concerns (shield, transients, local heat loads) are still present and should be studied and treated in 2017 Cryogenics for sc links, short update

5. Arc feed box Simplified scheme of a DFA box to replace DFBA next to Q7, + Many circuits RB, IPQ, correctors + Delicate interface with arc termination module to be looked at Same principle to be applied for new triplets Cryogenics for sc links, short update

6. HiLumi Triplet R5 flow scheme sc link Cryogenics for sc links, short update

7. P1/P5 Cryogenic architecture 18 kW equivalent at 4.5 K, including 3 kW at 1.8 K Warm compressor station SHE Following Cost to Performance exercise Summer 2016 (Performance - Cost - Risk) QSVB GHe storage tanks Surface piping SHM QSCG QSAG Dryer QSP Surface cold box SLN SD SLN QSDQ Quench tank QSRG QSDN Liquid Nitrogen tanks Surface Shaft QPP QPLG Vertical transfer line Underground US Cold compressors box QURCG DFHX DFHM (existing) DFBL UR UL DSHM QUIG DSHX DSL LHC tunnel Interconnection box Q1 Q2a Q2b Q3 CP D1 D2 CC CC Q4 Q5 Q6 QRP QXL Studies on-going for sc links HRL HiLumi Cryogenics (WP9) for 2nd C&S_Review_Oct'16

8. P1/P5 Cryogenic architecture 18 kW equivalent at 4.5 K, including 3 kW at 1.8 K Following Cost to Performance exercise Summer 2016 (Performance - Cost - Risk) 1. Main sc link, cooling flow driven by large currents 2. sc-link for D2, Not yet finalised, lower current w.r.t length 3. sc-link for Q4-Q5-Q6, under study depending on correctors (number, current rating, proven solutions) Underground US Cold compressors box QURCG DFHX DFHM (existing) DFBL UR UL DSHM QUIG DSHX DSL LHC tunnel Interconnection box Q1 Q2a Q2b Q3 CP D1 D2 CC CC Q4 Q5 Q6 QRP QXL Studies on-going for sc links HRL HiLumi Cryogenics (WP9) for 2nd C&S_Review_Oct'16

9. 1. Main sc-link D1-CP-Triplet • Principle of DFX identified, but double splice (MgB2-NbTi, NbTi-Nb3Sn) and plug to be studied in more details • Needs for beam screen (or not) to be made • Needs for 20K shield to be clarified: • Obvious gain in flexibility without thermal shield • Risk of local “hot spots”, like seen in some bends of existing DFBLC • Specific configuration of cable in helium jacket to be carefully looked at, like with double inverted helical spacers Cryogenics for sc links, short update

10. 2. sc-link for D2 • Not the most advanced due to recent baseline changes, and to integration of intermediate box DFM • Cooling margin of the link to be assessed, as same length but lower current rating than main sc-link • Same consideration for thermal shield as for main link DFHM D2 QXL Cryogenics for sc links, short update

11. 3. sc-link for Q4-Q5-Q6 • Under study, based on required correctors (number and current rating) and considering number of existing leads in DFBL and present solutions for local powering • With options considered for Q4, would be wise to consider a powering scheme that would not require a modification of the DSL link in the future (existing) DSL Q4 Q5 Q6 QXL • Difficult to imagine removing the existing QRL and installing new QXL and other hardware while keeping existing DSL link in place, but we will see when studied more advanced Cryogenics for sc links, short update

12. RR Present DSL link • QRL supply DFBL with cold He (blue) • DFBLD supplies current leads over DSL (orange) • HL-LHC-DFBs will be on the new service tunnel and will have DSLs to the SAMs • On the HL-LHC, the direction of the He flow to cool the current leads will be different: • LHC: QRL-DFBL-DSL-Magnet • HL-LHC: Magnet-DSL-DFBL-WarmRecovery

13. LHC situation of DSL_L5 QRL ARC S4-5 DSL Q6 New QXL LSS5L From DFBL_ Currentlyitis a SM type DC at 7L5 Return modules • Currently SM (at 7L5) receives current leads from DFBLD and delivers DSL. This will be removed. The DFBL and DSL will be routed diferently. • The new available space will be used for a special ServiceModule (at 7L5). It will be a kind of „QUIC“ to connect QRL S4-5 and QXL S5 (in other words Refr4-5 and Refr5) in case of need. • DSL coming from DFBLD and connected to Q4L5-D2L5 (orange) • SM cools the magnets independently from the current leads coming from the DSL (blue)

14. LHC - Existing solutions • Not shielded • Fed by link • OK for 6kA • Not shielded • 3 circuits (bus, LHe-GHe) • Low point with splice & plug (as for DFBA’s) • Adapted to magnet operation @ 1.9K • Need for thermal shied to be evaluated

15. Summary • The sc-link cooling principles were defined with the basic original cooling schemes. It is now time to update all that to match the 3 types (Triplet-D2-SAM) • The use of thermal shield is clearly a safe baseline, but alternative no-shield could be envisaged only if a specific effort is made on spacers to avoid hot spots • Many technical solutions combining cooling and powering were developed for LHC and have proven to provide required performance. We will have to review what deserves to be adapted and what needs new developments Cryogenics for sc links, short update