1. 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

2. 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

3. 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

4. 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

5. F. Lackner; Diode consolidation review
Material studies and choice for the LS-1
Ryton R – 40% GF reinforcement PPS compound
Ultem – transparent thermoplastic with characteristics similar to the related plastic PEEK
Ryton R – 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
F. Lackner; Diode consolidation review

6. Electrical insulation: qualification tests of busbar insulation in gaseous Helium @ RT
Test program to determine breakdown 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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