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INSTRUMENTATION FEEDTHROUGH SYSTEM FOR LHC MACHINE ARC QUADRUPOLE MAGNETS.

INSTRUMENTATION FEEDTHROUGH SYSTEM FOR LHC MACHINE ARC QUADRUPOLE MAGNETS. 123rd LHC Vacuum Design Meeting 19 April 1999. Introduction.

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INSTRUMENTATION FEEDTHROUGH SYSTEM FOR LHC MACHINE ARC QUADRUPOLE MAGNETS.

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  1. INSTRUMENTATION FEEDTHROUGH SYSTEM FOR LHC MACHINE ARC QUADRUPOLE MAGNETS. 123rd LHC Vacuum Design Meeting 19 April 1999

  2. Introduction • This presentation is based on the "cahier de charges" for the Instrumentation Feedthrough System for prototype SSS3/4 (2 + 1 spare) systems on the QQS side. • It was decided build design an I.F. System that is as close as possible to the probable LHC design. The system has to "feed-through" 75 wires (LHC will see between 40 and 60 wires). Some 53 additional wires will be fed out in a parallel system .... • This type of feedthrough system was never adopted at CERN and the first prototype system needs to be delivered 24 June 1999. This means that part of the "research" work needs to be done in parallel with the design work. Therefore, it is possible that a number of requirements will evolve with time (number of wires, test voltages etc.). The design cannot be adopted for each modification. Introduction

  3. Warm end feedthrough system Connections Warm end Feedthroughs Pressure sensor? Warm Ghe 1.3 - 20 bar Atmosphere, 293K Interface with cryostat Thermalisation? LHe level Min 2 tubes, tightly packed w. wires Wires Quench P Cold connection LHe, 1.9K 1.3 - 20 bar Interface with cold mass Insulation Vacuum Introduction

  4. Design Parameters General* vacuum Electrical Mechanical Cryogenic * based on LHC-PM-ES-0002.00 rev.1.0 Design Parameters

  5. General • Low cost, simplicity, manufactureability and reliability • System lifetime: 20 years * • Operating cost calculation time: 10 years * • Expected radiation doses: • at 10 cm of cold bore: 14 kGy / 20 years * • at 50 cm of cold bore: 0.3 kGy / 20 years * • (+ Neutron fluence: 1.2x1013 n/cm2 ?) • Safety requirements (e.g. IS 23/41) * based on LHC-PM-ES-0002.00 rev.1.0 Design Parameters

  6. Mechanical I • Operating Pressure: 1.3 bar * • Min. pressure: … ? ** • Max. pressure: 20 bar, max. duration 120 s (10 to 100 cycles) * • Max. rate of pressure rise: 100 bar/s * • Test pressure: 25 bar • Component leak rates: (Sub-assemblies = values x 10) ** • He to vac.: < 1.10-10 mbar l/s (st.steel welding) • He to/from atm.: ~ 1.10-8 mbar l/s (feedthroughs) • Atm. to vac.: ~ 1.10-8 mbar l/s (feedthroughs) * based on LHC-PM-ES-0002.00 rev.1.0 ** to be confirmed by LHC/VAC group/new reference document (ES) Design Parameters

  7. Mechanical II • Dimensional constraints, installability (in QQS) • Accessibility at interface(s) (electrical/mechanical) • The system (tubes) will be considered as an extension of the cold mass. Therefore, only the warm end is accessible /repairable (2-3 times?) during operating conditions. Design Parameters

  8. Cryogenic • Temperature range: 1.9 - 293 K (> 25 cycles) * • (Higher temperatures possible during mounting/installation) • Heat load budget: ~ 0.5 watt to 1.9 K (average value) • (Values could be different between the two types of SSS (with/without vacuum barrier) and the dipoles) • Max. cooldown rate: 1.56 K/hour * (to be confirmed) • Max. warmup rate: 5.2 K/hour * • Avoid freezing of warm box (during quench) • Avoid thermal oscillations (high heat loads) * based on LHC-PM-ES-0002.00 rev.1.0 Design Parameters

  9. Electrical • Number of Wires: 75 (+53) • Min. Design withstand voltage: max 1700 V (DC) • Max. expected working voltage: 600 V (DC) • Test voltages: 250 and 1000 or 1700 V (DC) • Resistance to overheating due to current pulsing • Reliable connection techniques (reliability, resistance) • Signals separated in at least 2 tubes (Vtaps/Heaters) Design Parameters

  10. Interdependency of main requirements = Strong influence = influence ?? Heat Loads Nbr. Wires Voltage Cost Leak rates Dimension Reliability Design Parameters

  11. Tubes & Boxes • Function: extension of the (20 bar) pressure vessel • He contained by st.steel and welding (except at feedthrough) • Tubes vertical around T and go “upwards” after this point ? • Access to warm end by cutting / welding • Tube length (3 - 5 m) and thermalisation points? to be optimised together with wires (see minimising heat loads) • GHe volume to be reduced to minimum to minimise compression of gas (= flow) during quench. • Interface with cryostat: ISO flange + O-ring (or welding?) • LHe volume (cold end) to be reduced to minimum? Warm end feedthrough system

  12. Wires* • Function: electrical connection from sensors to outside world • Test voltages to be determined • Operation from cold LHe to warm GHe • Mechanical strength for pulling through tubes / bending • Length / cross section (aspect ratio) to be optimised (see minimising heat loads) • Different requirements from wires inside cold mass (see connection techniques ) • To be protected during welding of box / tubes * point of discussion in new IWG sub-working group Warm end feedthrough system

  13. Minimising heat loads • Minimise number of (copper) wires • Use low heat-conducting conductor materials (manganine, st.steel) • Minimise cross sections of conductors* • Maximise wire (and tube) length* • Maximise wire packing factor inside tubes to lower LHe level (also reduces GHe volume) • Thermalise tubes? (No official budget for 50 and 4.6 K points..) • * Optimise wire aspect ratio taking into account all of the above + current carrying capacity, wire strength and size of tubes • Calculations have shown that there is no difficulty to stay within the 0.5 watt to 1.9 K budget. Warm end feedthrough system

  14. Connection techniques* • Possibilities: soldering, welding, crimping(?), use of connectors... • Warm end: unavoidable (wire meets feedthrough), operation in GHe ! • Cold end: Necessary for mounting the QQS + • Magnet handling during pressure testing, transport and cryostatting • High packing wire insertion and tube forming (separate from CM) • Change in type of wire (section, materials) between CM and IF System • Useful electrical interface during manufacture of cold mass * point of discussion in new IWG sub-working group Warm end feedthrough system

  15. Feedthroughs* • Function: electrical and hydraulic interface between GHe (or vacuum) and air • Operation in GHe ! , potting (epoxy) to be avoided, use pin spacing • Available in Industry • To be fitted with a length of soldered wire on the “GHe” side and welded to a flange. Fragile ! Do not touch with fingers ! Leak tested as an assembly. Connectors may be used on the “air” side * point of discussion in new IWG sub-working group Warm end feedthrough system

  16. Dipole Magnets • The design of the instrumentation feedthrough • system for the Dipole Magnets will be similar but • with the following major differences: • Possibly no interface at cold mass side required • Higher maximum (test) voltages: 3100 V • Less signals / wires: 30 - 40 • More (installation) space available • More tube length available The End

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