Shortening the long RQF/RQD busbar segments in points 1 and 5

1. Shortening the long RQF/RQD busbar segments in points 1 and 5 Presented by Sandrine Le Naour with the helpful collaboration of TE-MSC-LMF Third LHC Splice Review

2. Outline • Present situation on RQF/D bus segments • Technical solution • Quality control • Time estimation • Conclusion Third LHC Splice Review

3. RQF/D bus segments in point 1 and 5 • In the arc, most of MQ busbar segments contain 8 splices (go through 6 dipoles + 2 quadrupoles, ~107m) • In point 1 and 5 , long bus segments (> 400m long) connect the main quads Q12 to Q11 via 32 splices. • These bus segments go from Q11 to the Q7 and return in the DFBA shuffling module to Q12 (Q10, Q9, Q8, Q7 are MQM magnets and are individually powered in point 1 and 5) Connection cryostat Third LHC Splice Review

4. RQF/D bus segmentsin point 1 and 5 • In LHC, 8 MQ segments contain 32 splices (RQF/RQD, R side, L side, point 1 and 5) • For these segments, if we consider 31 correct splices (with a resistance of 0.3nW), the Max Resistance of one of the splices is Rmax = Rsegment-(n-1)*Rsplice • For LS1, we suggest at the moment to redo completely all splices in a RQ segment if Rmax > 2nW. (Threshold is 0.82 nWfor dipole segments) • With this criteria 102 splices in RQ lines will be de-soldered and re-soldered and the 2 first segments concern already 64 splices! Third LHC Splice Review

5. RQF/D bus segments in point 1 and 5 • We propose to shorten the RQ bus segment after the magnet Q11. • The segments will be only 50m long (instead of 400m long), easier to protect • Only 6 splices in the segment (instead of 32) • 13 interconnections in RQ lines do not need to be open, reinforced and qualified ( that concern 208 splices which 52 must be completely redone – 104 sleeves not opened) • No change on instrumentation (only soft parameters for QPS) • … But the MQ line will be cut after the connection cryostat Connection cryostat Third LHC Splice Review

6. RQF/D bus segments in point 1 and 5 • Better to not leave active bus lines where they are not needed • No Impact for HL-LHC At the moment, no project is retained to power additionnal magnet(s) on RQF/RQD circuits (BE-ABP is informed). • No Electromagnetic Impact: M1 and M2 are no more actived between MB11 and Q7 (only M3 stays) negligeable effect (S. Russenschuck) Connection cryostat Third LHC Splice Review

7. LHC configuration : Room available • L side • R side QuadrupoleBellow zoneSleeve zone ConnectionCryostat L=217mm, D=80mm L=207mm, D=100mm Connection Cryostat Bellow zoneSleeve zone Quadrupole Third LHC Splice Review

8. Proposed solution • Direct U turn To connect properly the 2 splices, the 2 bus bars are twisted by 90deg. and a superconducting cable covers the 2 cables of the interconnection. The assembly is then stabilized with a massive copper piece. The twisting of the busbardoesn’t damage the SC filaments. The performance of the busbar out of magneticfield ≥ 40kA ! Third LHC Splice Review

9. A first prototype Third LHC Splice Review

10. Quality Control : Gamma Ray • Nice connection shown by g-rayradiography. Frombusbar to busbar via the central piece (act as a shunt) and along the SC cables. • As only 8 such connections will be done in 2 points, a gamma-ray inspection will be performed systematically. • Spool piece lines will be open for a better access to the main busbar, but it is also a request from ElQA for the qualification of each individual line (spool piece + spare) during the progress of the train. Thanks to EM-MME-MM for the radiographies Third LHC Splice Review

11. Quality control : Electrical test • A QC report is written on the 2 first prototypes : EDMS 1240171 Similarly to R8/R16 qualification at room temperature, R5 and R3 resistance measurements will be performed: R5 from busbar to central piece R5 expected value ≤ 6 µΩ R3 from busbar A to busbar B at the level of the shunt (green points) R3 expected value ≤ 4 µΩ Thanks to TE-MSC-SCD Test 1 : unsoldered shunt Test 2 : soldered shunt Third LHC Splice Review

12. Insulation of the connection The insulation box will be similar to the one for the quad connection, with a comb piece for the spool piece. Eccobond bag will be also included The cut busbars will be included in the insulation box and one leg will be connected to ground. Hydraulic section still sufficient for helium circulation (A. Perin) Third LHC Splice Review

13. Time estimation • Time gain for the train (normal teams) : 5-6 days • Time to implement the new connection in Q11 (train special team): 1day/circuit = 8 days • Time estimated to change flanges (SIT) : 4 days • Time estimated to reconnect of spool pieces lines (SIT + ElQA) : 2 days • Gamma ray : 2 or 4 nights - 6 days +8 days +4 days -2 + 2 days 0 days +6 days but with new flanges ! Third LHC Splice Review

14. Conclusion 1/2 • We propose to shorten the long RQ busbar segments which connect Q11 to Q12 in points 1 and 5. • Reduce them to 50m long and 6 splices instead of 400m long and 32 splices. Deactivation of over-length busbars. • In 4 sectors, 13 interconnections (M1 and M2) don’t need to be open, reinforced, qualified… (it concerns 208 splices which 52 must be re-soldered because of Rmax criteria at cold). So the risk to damage spool pieces busbar is reduced. • No impact for the HL-LHC project. • Despite a small volume available for a special connection, the direct U turn is an easy configuration to implement. • Gain of time for the regular teams but additional work for the special teams (One of the train + SIT). • The cost is negligeable. Third LHC Splice Review

15. Conclusion 2/2 • This project was presented to the splice task force, TE departementtechnical meeting (TE-TM) and the LHC Machine Committee (LMC). All teams support the project. • Next steps • Training on the mockup for a last adaptation of the tooling and insulation • Test at cold. • Thermal choc in N2,liq done successfully • Test at 4.2K to be performed • Documentation (ECR) Third LHC Splice Review

16. Third LHC Splice Review Thankyou

17. LHC Bus Bar Max Splice Resistances, 2010-2012 Normal: 99.7%=532pΩ (53) L-L: 99.7%=801pΩ (10) 27 splices • Conclusion: • Measurement error on 700 rumps statistics is about 100±25pΩ for RB and RQ; • Relatively good 3 params fit found for both circuits; • 3σ is 0.8nΩ for RB circuit and 2.1nΩ for RQ circuits; • It gives about 27 + 38 = 64 splices to be redone if will be applied as a safe criteria; Normal: 99.7%=1.17nΩ(30) L-L: 99.7%=2.15nΩ (7) 38 splices + 2*32 Third LHC Splice Review

18. Reversibility If M1 and M2 lines must be reactivated for a future project (hypothesis), it is considered up to now that the empty cryostat will be changed (for a new dimension, for example) and then reconfigured for a possible connection with the Q11 magnet. If a “quick re-connection” must put in place ( but13 interconnections are not consolidated), the superconducting cable can be kept, copper stabilizer removed on 40-50 mm to gain cable flexibility. The SC cable will be attached to the insulation box. Additionnal time estimated : 1 day per circuit. Third LHC Splice Review

19. Still to do If the projectisaccepted • Finalise the design of the shortcut (in progress) • Tooling (in progress) • Design of the insulation of shortcut and insulation of the desactivatedbusbar (leftfloatting). • Put the shortcut in place on a interconnectionmockup • A method to qualify the shorcut (eqv R8-R16) • Estimate the hydraulicdiameter • Do a cold test for the final solution (Still to define). • … Third LHC Splice Review

20. Busbar segments of Main quad circuits at odd points x=1,5 Connection cryostat x=3, 7 Connection cryostat Third LHC Splice Review

21. Estimation of electromagnetic forces Calculated by Susana Izquierdo Bermudez Third LHC Splice Review