First Internal LHC Dipole Diode Insulation Consolidation Review Material Choice First Internal LHC Dipole Diode Insulation Consolidation Review 10 October 2017 F. Lackner - TE-MSC-LMF With inputs from R. van Weelderen, C. Scheuerlein, T. Sahner, L. Grand-Clement, H. Prin, J.P. Tock

F. Lackner; Diode consolidation review Outline Material choice and testing, experience from the main splice insulation system installed on the busbars during the LS-1 Design optimization of diode insulation insert using FEA First preliminary FEA results Conclusions F. Lackner; Diode consolidation review

Material Requirements, environmental boundaries 5 kV gaseous Helium 1.9 K 0.3 MGy 5 bar pressure difference Mechanical robustness Radiation environment Withstand voltage Cryogenic compatibility C. Scheuerlein, Functional specification for the consolidated LHC dipole diode insulation system F. Lackner; Diode consolidation review

F. Lackner; Diode consolidation review Material Requirements, Environmental boundaries Mechanical properties Thermal properties Withstand current Water absorption, porosity and surface roughness due to the molding process Radiation behavior Mold shrinkage Increased complexity of load case during the LS1 Superconducting Magnets and Circuits Consolidation (SMACC): Fatigue effect on splice interconnection due to the transversal Lorentz forces. F. Lackner; Diode consolidation review

F. Lackner; Diode consolidation review Material studies and choice for the LS-1 Ryton R-4-200 – 40% GF reinforcement PPS compound Ultem 1000 – transparent thermoplastic with characteristics similar to the related plastic PEEK Ryton R-7-200 – glass/mineral filled PPS compound IXEF 1022 – 50% GF reinforced polyarylamide compound Vectra A 130 – 30% GF reinforced Liquid Crystal Polymer Fortron 1140 – 40% GF reinforced PPS compound Albis – 40% GF reinforced PPS Ultem XP60 – XP80 – XP 110 – Open cell Polyetherimide foam with density 60, 80, 110 kg/m3 Airex – Thermoplastic foam with closed cell Permeability test in collaboration with cryogenic and vacuum group All test results are still available via the insulation study website. Fortron Ryton R4 Ryton R7 Vectra A. Gerardin, “Mechanical Testing of Candidate Materials for the Splices Insulation -3-” CERN Quality test, EDMS Nr. 1209952. F. Lackner; Diode consolidation review

Electrical insulation: qualification tests of busbar insulation in gaseous Helium @ RT Test program to determine breakdown strength @ 1 and 0.1 bar: from bus bar to bus bar from bus bar to spools from bus bar to sleeve Test carried out on different types of samples: Standard insulation wrapped around the bus bars Present insulation in the LHC interconnections Proposed design to insulate dipole and quadrupole busbars in the interconnections Tests voltage on HV electrode 1kV/s until breakdown Courtesy of J. KOSEK F. Lackner; Diode consolidation review

F. Lackner; Diode consolidation review Results of the qualification tests Improved insulation design has increased the breakdown voltage above LHC design parameters F. Lackner; Diode consolidation review

F. Lackner; Diode consolidation review ULTEM 1000 ULTEM 1000® fatigue characteristics:§ Gamma irradiation: Dielectric strength of Ultem 1000 as a function of thickness Effect of gamma radiation exposure on tensile properties of Ultem 1000 Fatigue behavior: Fatigue behavior in comparison to higher charged ULTEM composites: Uniaxial fatigue test of Ultem at different glass ratios. F. Lackner; Diode consolidation review

F. Lackner; Diode consolidation review 1st iteration on FEA was based on previous insulation insert design: Version 1 Version 2 Design iterations (T. Sahner, EN-MME) First design iteration during summer 2017: Thermal stress during cool-down Mechanical stresses during quench event Stresses during assembly can be limited by using well defined torque Modeling of clamping still to be developed F. Lackner; Diode consolidation review

F. Lackner; Diode consolidation review Meshing and convergence Version 1 Version 2 4 nodes in thin walls based on Tet10 meshing. When these shape functions are use to approximate a three-dimensional problem, the resulting elements will give continuity in the approximated function across element boundaries F. Lackner; Diode consolidation review

Mechanical load case, static pressure difference 5 bar 1st iteration based on a static pressure to get knowledge on convergence and induced stresses & displacements Support assumed only via the fixation screws Ultem 1000 material used during first FEA Total deformation Development of FEM model and convergence Improving choice of elements and meshing parameters Understanding of critical design parameters Equivalent stress F. Lackner; Diode consolidation review

F. Lackner; Diode consolidation review New design and ongoing FEA computation Insulation, Ultem - Ryton PPS - PEHD M6 316LN Possible constraints during assembly, cool down and operation: RT: Assembly stress due to screw fixation 1.9 K: Relative thermal contraction between insulation and support plate Quench: Induced mechanical stress at 1.9 K due to pressure wave F. Lackner; Diode consolidation review

F. Lackner; Diode consolidation review Ongoing computation for further design optimization Assumed static pressure of 0.5 MPa on front surface due to the He in-flow direction (Talk: Rob Van Weelderen) Displacement support from backsite Fixation of the insert via two M6 screws First iterations computed based on the ULTEM 1000 material Boundary conditions Min [MPa] Max [MPa] Equivalent stress (von Mises) 38 Normal stress (X Axis) -43 11.5 Normal stress (Y Axis) -24 Normal stress (Z Axis) -28 15 Equivalent stess F. Lackner; Diode consolidation review

F. Lackner; Diode consolidation review Conclusions: Good understanding of insulation material characteristics from test results obtained throughout the development of the LHC busbar splice insulation We are confident to find a suitable material meeting all necessary requirements Design optimization of the insulation insert based on FEA has started and is ongoing Less complexity due to reduced amount of load conditions, thanks to the experience with the the Superconducting Magnets and Circuits Consolidation (SMACC) we are confident to develop a robust design F. Lackner; Diode consolidation review