1. Mike Struik / LHC-CRI INSTRUMENTATION FEEDTHROUGH SYSTEM FOR LHC MACHINE ARC QUADRUPOLE MAGNETS. 123rd LHC Vacuum Design Meeting 19 April 1999

2. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 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. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 Warm end feedthrough system Introduction Cold connection Warm end Feedthroughs Min 2 tubes, tightly packed w. wires LHe, 1.9K 1.3 - 20 bar Insulation Vacuum Atmosphere, 293KInterface with cryostat Interface with cold mass Wires Connections LHe level Warm Ghe 1.3 - 20 bar Quench P Pressure sensor? Thermalisation?

4. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 Design Parameters General* Cryogenic ElectricalMechanical vacuum * based on LHC-PM-ES-0002.00 rev.1.0 Design Parameters

5. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 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: 1.2x10 13 n/cm 2 ?) Safety requirements (e.g. IS 23/41) * based on LHC-PM-ES-0002.00 rev.1.0 Design Parameters

6. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 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. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 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. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 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) Design Parameters * based on LHC-PM-ES-0002.00 rev.1.0

9. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 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. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 Interdependency of main requirements Cost Dimension Heat Loads Reliability Voltage Nbr. Wires Leak rates ?? = Strong influence = influence Design Parameters

11. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 Tubes & Boxes Warm end feedthrough system 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?

12. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 Wires* * point of discussion in new IWG sub-working group Warm end feedthrough system 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

13. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 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. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 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. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 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. Mike Struik / LHC-CRI Instrumentation Feedthrough Systems LHC Vacuum Meeting 19 April 1999 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