LHC Dipole Diode Insulation Consolidation Review (I) INTRODUCTION J.Ph. Tock (TE-MSC)

LHC Dipole Diode Insulation Consolidation Review (I) Introduction Why ? Scope (Dipole diodes only, not the quadrupole ones) Where are we now ? Conclusions LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017

LHC Dipole Diode Insulation Consolidation Review (I) Introduction Why ? LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017 Courtesy M Bednarek

LHC Dipole Diode Insulation Consolidation Review (I) Introduction The LHC dipole diode stack Why ? Half Moon (Diode side) Diode box BB to Heat sink connection Upper Heat Sink Lower Heat Sink More details in next presentation LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017

LHC Dipole Diode Insulation Consolidation Review (I) Introduction Previous short circuits in dipole diode containers Why ? Presence of metal (not only) debris in the cold masses, residues from the manufacturing is known. The mechanism is also known This can create a short to ground At room temperature, the corrective intervention is straightforward and short (a few days) LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017

LHC Dipole Diode Insulation Consolidation Review (I) Introduction Why ? Previous short circuits in dipole diode containers # EDMS Date Sequence R short [Ohm] Secteur Location Magnet Temperature 1 745903 Jun-06 Installation 45 30R4 2152 RT 2 853097 Jun-07 Installation (TBC) 30L5 3186 3 871858 Oct-07 After flushing 81 B11L1 1158 4 883010 Nov-07 Cool down ? 56 B15L6 2264 5 888746 Jan-08 B30R8 1164 6 1285057 May-13 After warm-up 12 B30L2 2409 7 1314329 Sep-13 0.2 A30R8 3141 8 1502332 Mar-15 During training 1.2 34 C19L4 2174 Cryo 9 1741891 Dec-16 0.5 C12L4 1127 9 (TBC) shorts to ground in dipole diode containers since June 2006 No correlation with sector or magnet manufacturer LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017

LHC Dipole Diode Insulation Consolidation Review (I) Introduction Why ? Previous short circuits in dipole diode containers # EDMS Date Sequence R short [Ohm] Secteur Location Magnet Temperature 1 745903 Jun-06 Installation 45 30R4 2152 RT 2 853097 Jun-07 Installation (TBC) 30L5 3186 3 871858 Oct-07 After flushing 81 B11L1 1158 4 883010 Nov-07 Cool down ? 56 B15L6 2264 5 888746 Jan-08 B30R8 1164 6 1285057 May-13 After warm-up 12 B30L2 2409 7 1314329 Sep-13 0.2 A30R8 3141 8 1502332 Mar-15 During training 1.2 34 C19L4 2174 Cryo 9 1741891 Dec-16 0.5 C12L4 1127 LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017

LHC Dipole Diode Insulation Consolidation Review (I) Introduction How to solve this at cold ? Why ? Warming-up a sector, solving the NC and cooling it down : ≈ 3 months  (Too) huge impact on operation See risk analysis in next presentation This method was successfully applied twice but is not risk free (and depends on the fault characteristics) > 2 orders of magnitude on R value If necessary, a dedicated presentation can be given later LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017 Courtesy M Bednarek

LHC Dipole Diode Insulation Consolidation Review (I) Introduction Why ? LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017 Courtesy M Bednarek

LHC Dipole Diode Insulation Consolidation Review (I) Introduction CMAC Recommendation Why ? Perform a quantitative risk analysis of the impact of potential problems caused by magnet training [and operation] and develop a mitigation plan. Study the possibility to (remove debris in all magnets, to clean and) better insulate the diode boxes and establish the necessary time and resources required to do it. LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017

LHC Dipole Diode Insulation Consolidation Review (I) Introduction Insulating half moon pieces Why ? Installed on 15% of the cryodipoles LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017

LHC Dipole Diode Insulation Consolidation Review (I) Introduction Why ? Previous short circuits in dipole diode containers # EDMS Date Sequence R short [Ohm] Secteur Location Magnet Temperature 1 745903 Jun-06 Installation 45 30R4 2152 RT 2 853097 Jun-07 Installation (TBC) 30L5 3186 3 871858 Oct-07 After flushing 81 B11L1 1158 4 883010 Nov-07 Cool down ? 56 B15L6 2264 5 888746 Jan-08 B30R8 1164 6 1285057 May-13 After warm-up 12 B30L2 2409 7 1314329 Sep-13 0.2 A30R8 3141 8 1502332 Mar-15 During training 1.2 34 C19L4 2174 Cryo 9 1741891 Dec-16 0.5 C12L4 1127 All cases were in dipole where insulating pieces are not installed (85%) This has a low statistical significance (At least no counter-example) This nevertheless tends to show that, when installed, a good (sufficient ?) level of protection is achieved LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017

Why not consolidating quadrupole diodes insulation ? Comparison with main dipole circuits : No short circuit in quadrupole diodes containers (so far) About 1/3 of magnets (wrt dipole magnets) Energy stored : 25 MJ (<< 1350 MJ for the dipoles) [2%] Time constant : much lower ≈ 33 s (< ≈ 105 s for the dipoles) Much less quenches for training and during operation Hydraulic configuration is favourable (less risk to have debris transported to the quad diode container)  next slide Better insulated than the dipole diodes Present insulation level is the same as the one that will be achieved in dipole diodes after implementing the proposed consolidation LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017 Based on a presentation of L Grand-Clement

Why not consolidating quadrupole diodes insulation ? LHCLQMJS0001 Insulation pieces Tube 168.3x2.6 He Helium flows to the diode stack from behind Most of debris likely blocked by the insulation pieces behind the diode The insulation sleeve is already in the container unlike MB diode It insulates all active parts of the diode stack with respect to ground LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017 Based on a presentation of L Grand-Clement

Why not consolidating quadrupole diodes insulation ? All quadrupole diodes have been consolidated during LS1 Much less debris than in the dipole containers All were cleaned during LS1 All NCs (from assembly) have been corrected during LS1 Worst cases < 10 / 392 Quadrupole diodes insulation is as robust as dipole ones after the proposed consolidation No need to intervene on the quadrupole diodes LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017 Based on a presentation of L Grand-Clement

LHC Dipole Diode Insulation Consolidation Review (I) Introduction Where are we now ? What happened since end January 2017 ? A task force was set-up involving CRG, MPE, MSC (7 meetings) + Scope of the project was defined + Consolidation decided / approved by ATSMB on 1.06.2017 Priorities during LS2 P0 : Safety P1 : Activities needed to reach 300fb-1 during run 3 P2 : HL-LHC & LIU projects P3 : Approved projects P3A: Approved project if budgeted* P4 : Approved studies P5 : Others LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017

A consolidation was defined, based on 3 main pillars Where are we now ? What happened since end January 2017 ? A technical working group started (February 2017) [C Scheuerlein] (Thank to all participants – not a planned activity) A consolidation was defined, based on 3 main pillars Removal of accessible debris Improvement of bare diodes BB Installation of optimised half-moon insulation pieces Will be the subject of the next presentations LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017

LHC Dipole Diode Insulation Consolidation Review (I) Introduction Conclusions The consolidation of the LHC dipole diodes insulation is required before training campaigns to go to 7+ TeV (Design/ultimate energy for run III) A technical solution consisting in : Installing optimised half moon insulating pieces Reinforcing the present insulation Removing the accessible metal debris is under development Quadrupole diodes insulation does not have to be consolidated No CSCM is needed Achievements from the last months will be presented A preliminary solution has been developed that needs to be confirmed by detailed calculations and mechanical, electrical and cryogenic validation tests. This is the opportunity to incorporate review outcome Inputs from the committee are WELCOME Recommendations on most important criteria Points missing (design, qualification,…. organisation) Are we on good track to be successful in consolidating LHC dipole diodes insulation during LS2 and increasing safely the LHC centre of mass energy (> 13 TeV,  15 TeV) What should we focus on ? What is critical ? LHC Dipole Diode Insulation Consolidation Review (I) Introduction J.Ph. Tock (TE-MSC) 10.10.2017

Based on a presentation of S Le Naour Insulating half moon pieces Why ? Radiographic inspections done: During LS1 (W-bellows open) For the 2 earth faults during training (W bellows closed) During this EYETS (W bellows closed) 10.10.2017 Based on a presentation of S Le Naour

Based on a presentation of S Le Naour Insulating half moon pieces Why ? Radiographic inspections allow to check the presence of the protection About 15 % of the dipole diodes are protected 53 diodes have been analysed 10.10.2017 Based on a presentation of S Le Naour

Next steps Functional specification of the LHC dipole diodes insulation for Summer Internal design review for October 2017 Design finalised and first components in Autumn Testing in SM18/cryolab end 2017 Spring 2018: Final design and project readiness review December 2018 : Ready to start Summer 2020 : End of the project 10.10.2017

Based on a presentation of A Verweij Risk analysis in a nutshell Why ? Probability of O(1%) [2/254* quench events since 2014] to have a single short to ground per quench event at high current Probability of O (0.01%) to have a double short to ground dissipating sufficient energy to melt a hole in the helium enclosure O(500) training quenches required to reach 7 TeV [E Todesco@Chamonix] 2 shorts at cold were solved using the EFB. Reliability ? Time taken ? Risk ? Non-negligible O (5%) (non-acceptable?) probability to have a double short to ground with major consequences *including the 2 training quenches in S12 for the recommissioning in 2017 Study the possibility to reinforce the (dipole) diodes insulation during LS2 (2019-20) 10.10.2017 Based on a presentation of A Verweij

First Internal LHC Dipole Diode Insulation Consolidation Review Introduction J.Ph. Tock (TE-MSC) 10.10.2017