CERN Geneva European laboratory for Particle Physics What

CERN, Geneva (European laboratory for Particle Physics)

What is CERN ? CERN is the European Organization for Nuclear Research, the world's largest particle physics centre. Here physicists come to explore what matter is made of and what forces hold it together. Founded in 1954, the laboratory was one of Europe's first joint ventures and includes now 21 Member States. Size: 490 ha F, 112 ha CH Budget : 1280 MCHF (~825 MEuros) 2014: 21 Member States: A, B, BU, CH, CK, D, DK, E, F, GB, GR, H, I, N, NL, P, S, SF, SK, IL L. Dassa 04. 09. 2014 2

Who works at CERN ? CERN employs representatives of a wide range of skills - physicists, engineers, technicians, craftsmen, administrators, secretaries, workmen, … Staff members: ~2550 ~81 physicists in research ~977 engineers ~862 technician ~427 clerks and administrative ~203 hand workers Fellows: 215 Scientific associates : 293 Users: ~ 6200 coming from 483 institutes and universities with 80 nationalities And about 2000 peoples from external enterprises L. Dassa 04. 09. 2014 3

The Large Hadron Collider (LHC) The LHC, the world’s largest and most powerful particle accelerator, is the latest addition to CERN’s accelerator complex. It mainly consists of a 27 km ring of superconducting magnets with a number of accelerating structures to boost the energy of the particles along the way. Some numbers: ~ 5, 000 LHC superconducting magnets ~ LHC cryogenics need 40, 000 leak-tight pipe junctions ~ 12 million liters of liquid nitrogen are vaporized during the cool down of 31, 000 tons of material and the total inventory of liquid helium is 700, 000 liters. L. Dassa 04. 09. 2014 4

ATLAS: A generic LHC experiment / CMS: Compact Muon Solenoid L. Dassa 04. 09. 2014 5

EN/MME GROUP 1 INTERNAL CONTRAT (30 P. ) & 2 EXTERNAL CONTRATS L. Dassa 04. 09. 2014 6

Mechanical & Materials Engineering The MME group is in charge of engineering support for the maintenance of CERN facilities and the manufacturing of prototypes as required for CERN projects. This encompasses various activities such as the mechanical design and manufacturing, as well as the selection, the characterization and the treatments of surfaces and materials. The drawing tools that we are using are : AUTOCAD© Mechanical and CATIA © L. Dassa 04. 09. 2014 7

Metallic Productions : Niobium-Titanium, Niobium-Tin, Copper… Linac 4 CLIC RF Module L. Dassa 04. 09. 2014 8

Metallic Productions : Copper, Niobium, Stainless Steel… RF Cavity Isolde Cryo-Module LHC RF Cavity SPL L. Dassa 04. 09. 2014 9

Metallic Productions : Tungsten, Carbon, Glidcop, Macor… LHC Collimator Jaw PS Pick-Up L. Dassa 04. 09. 2014 10

Composite Productions : Fiber Glass Epoxy BUSBAR Insulation Coil Spacer L. Dassa 04. 09. 2014 11

Some project: cryostat for superconducting cables (1) L. Dassa 04. 09. 2014 12

Some project: cryostat for superconducting cables (2) L. Dassa 04. 09. 2014 13

Some project: standard and “special” pressure equipment He guard (SM 18) Bolts able to hold up the pressure load Insert for cryostat (superconducting magnet test station) Bolts at cryo T, often with heavy load) L. Dassa 04. 09. 2014 14

Bulten screws at CERN: LHC long straight section Common use at CERN for UHV: Bufab (ex Bulten) hexagon head screw, class A 4 -100, 316 L stainless steel • • bolts nuts washer (machined in A 4 -100) threaded rod in A 4100 A 4 -100 used because the deformation during baking is lower than A 4 -80. It is better for sealing tightness. L. Dassa 04. 09. 2014 15

Tightening test bench (1) • Design Office request : - Development of a tightening test bench to evaluate the force applied on the structure versus the tightening torque; - Evaluation of the friction coefficients for several materials of screws and supports - Application range: M 2 to M 20 • Collaboration: - Design of the setup : - Instrumentation (Force sensor, torquemeter) - Validation tests - Validation results Design Office (MME) Measurements lab (MME) MME Courtesy of M. Guichard (EN-MME-EDM) L. Dassa 04. 09. 2014 16

Tightening test bench (2) Theoretical Approach Γ : Tightening torque [N. m] F : Force obtained during tightening [N] D : Maximum diameter of the support [m] d : Nominal diameter[m] γ : Helix angle [rad] ρ : Friction angle [rad] p : Pitch [m] d 2 : Thread diameter [m] αa : Thread flank angle [rad] μ 1 : Thread friction coefficient μ 2 : Screw head friction coefficient Courtesy of M. Guichard (EN-MME-EDM) L. Dassa 04. 09. 2014 17

Tightening test bench (3) Torquemeter ± 0. 2% Test bench Screw Force sensor ± 0. 5% Courtesy of M. Guichard (EN-MME-EDM) L. Dassa 04. 09. 2014 18

Tightening test bench (4) Results 5 exp M 10 steel black exp M 10 Inox exp M 10 steel clean theo M 10 u 1=0. 12, u 2=0. 15 Γ=f(F) Torque (Nm) 4 3 2 1 0 -2. 5 5 -1. 5 Force (k. N) -0. 5 exp M 8 steel black exp M 8 steel clean exp M 8 Inox theo M 8 u 1=0. 12, u 2=0. 15 Γ=f(F) Torque (Nm) 4 3 2 1 0 -2. 5 -1. 5 -0. 5 Force (k. N) 0. 5 Courtesy of M. Guichard (EN-MME-EDM) L. Dassa 04. 09. 2014 19

LHC diodes: bolted joints characterisation (1) 2001 to 2007 to … Torque (Nm) 5. 5 10 Screw M 6 x 20 M 6 x 25 Washers Flat one in stainless steel 4 Cu. Be spring washers 8. 5 Maxi 10 Length of engagement in the heatsink (mm) GOALS : • To verify the behavior of the bolted joints at warm/cold, including the spring washers; • To check consistency with the expectations ; • To verify the behavior of the big washers that preload the diode. LHCDQDDP 00021 Courtesy of M. Guichard (EN-MME-EDM) L. Dassa 04. 09. 2014 20

LHC diodes: bolted joints characterisation (2) Base line With Loctite After Loctite 5. 8 k. N @10 Nm 7. 4 k. N @10 Nm 6. 8 k. N @10 Nm L. Dassa 04. 09. 2014 21

LHC diodes: bolted joints characterisation (3) Hardness versus position 180 160 140 HV 0. 025 120 100 80 60 40 20 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 L. Dassa 04. 09. 2014 22

LHC diodes Bolted joints characterisation (4) In-situ bolted joints evaluation – Correlation with FEA Contact bolt –bus bar Location of the strain gages z Spring washers (assumed to be completely flat) zoom Bus-Bar r Bolt M 6 x 20 Heat sink Courtesy of M. Guichard (EN-MME-EDM) L. Dassa 04. 09. 2014 23

LHC diodes Bolted joints characterisation (5) • The engagement length of the bolted joints (Heatsink / busbar) is very close to the design limit according to the VDI ; • The initial compression force generated by the screw is equivalent to 7 k. N for 10 Nm for a baseline configuration ; • The assembly cycles and loctite can degrade the compression force provided by the screws ; • The loctite can generate a very bad resistance contact ; • The assembly of 4 M 6 Spring washers in Cu. Be provide a spring effect up to 8 k. N ; • For the baseline configuration (M 6 x 25, 4 spring washers, 10 Nm), the stress evolution with thermal cycles is stable; • Experimental results confirm the FEA calculation performed on the sub-systems. Courtesy of M. Guichard (EN-MME-EDM) L. Dassa 04. 09. 2014 24

Discussion L. Dassa 04. 09. 2014 25

Questions for discussion (1) • PED compliance? “BUMAX 88 is the first bolt on the market with PMA approval (Particular Material Appraisal) under PED 97/23/EC. ” • Special order? Every Bumax 88? Material certificate? Courtesy of Bufab L. Dassa 04. 09. 2014 26

Questions for discussion (2) • High strength bolts: test at cryo T? test at high T? Radiation? • Raw material (bars) in high strength stainless steel? ? • Exotic material for screws (Inconel, Titane – for experiment -, …) Courtesy of Bufab L. Dassa 04. 09. 2014 27

Questions for discussion (3) • Cryogenic tests: reports? • High temperature tests: reports? • Radiation performances? Tests? Effects on structure? On the new materials? L. Dassa 04. 09. 2014 28

Questions for discussion (4) • Magnetic permeability? Test reports? Courtesy of Bufab L. Dassa 04. 09. 2014 29

Questions for discussion (5) • Are you interested in special coatings? • Molykote coating on bolts (issues with thickness? / some optimization? 10 cycles? Today after some cycle they are replaced) • Kolsterising / Bodycote? • Could you mark a set of screw with special CERN stamps? Which is the minimum amount of pieces? L. Dassa 04. 09. 2014 30