1. 1 MICE Mtg Oct 2002 Elwyn Baynham RAL Focussing Absorber Magnet Elwyn Baynham ; Tom Bradshaw Iouri Ivaniouchenkov ; Jim Rochford Applied Science Division Rutherford Appleton Laboratory

2. 2 MICE Mtg Oct 2002 Elwyn Baynham RAL Scope of Presentation l Scope »Magnetic Modelling »Conductor specification »Force reaction »Cooling »Integration with absorber »Manufacturing routes

3. 3 MICE Mtg Oct 2002 Elwyn Baynham RAL Solenoid absorber assembly

4. 4 MICE Mtg Oct 2002 Elwyn Baynham RAL Design Parameters

5. 5 MICE Mtg Oct 2002 Elwyn Baynham RAL Design Parameters l Opera3d model l Coil Pair at Z= 0 (mm) l Radial cross section 255 to 336 (mm) l Axial cross section 125 to 342 (mm) l Current Density: +/-105.88 (A/mm2) l Total current: 1.86E+06 (A) l Peak fields 6.04T l Stored energy 2 Mj

6. 6 MICE Mtg Oct 2002 Elwyn Baynham RAL Magnetic Modelling l Aspects modelled »Field Profiles »Peak Fields »Forces »Stored Energy/Inductance matrix

7. 7 MICE Mtg Oct 2002 Elwyn Baynham RAL Field Profile l Field Profile for central focusing pair

8. 8 MICE Mtg Oct 2002 Elwyn Baynham RAL Peak Field Profile l Peak Field Map

9. 9 MICE Mtg Oct 2002 Elwyn Baynham RAL Forces l Forces

10. 10 MICE Mtg Oct 2002 Elwyn Baynham RAL Stresses l Hoop stresses

11. 11 MICE Mtg Oct 2002 Elwyn Baynham RAL Stored Energy Computation l Stored Energy /Inductances

12. 12 MICE Mtg Oct 2002 Elwyn Baynham RAL Protection Philosophy l Powering – 3 sets of focus coils to be powered in series –one pair of leads for each coil to allow field trimming l Protection –by resistor/diode bypass of each coil –energy dumped/coil is self energy –coupled energy is relatively small –no active protection is seen as necessary –modelling is not yet done

13. 13 MICE Mtg Oct 2002 Elwyn Baynham RAL Conductor Specification/Op margins

14. 14 MICE Mtg Oct 2002 Elwyn Baynham RAL Cooling principles l Proposed cooling mode »2-phase circulation in pipes - pumped l Established for detector magnets –Generally high stability – pure aluminium –Large deltaT > 2K l Advantages –No helium vessel –Small helium inventory – single magnet <10 litres l Disadvantages –Require some deltaP/deltaT for circulation – 0.2-0.3K l Transient stability is the same as a bath

15. 15 MICE Mtg Oct 2002 Elwyn Baynham RAL Cooling - force transfer principles l Cooling-force transfer in cold mass

16. 16 MICE Mtg Oct 2002 Elwyn Baynham RAL Force Transfer to the cryostat l Schematic of force control 150T 225T Internal force restraint Internal axial force restraint Suspension External axial force restraint Between cryostats 75T LH

17. 17 MICE Mtg Oct 2002 Elwyn Baynham RAL Integration and assembly l Principles »Solenoid cold mass main structural element –cooled to 4K by 2 phase He –supported from vessel low heat leak supports –able to be pre-tested as a separate unit »H2 Absorber mechanically mounted from the solenoid cold mass –thermally isolating - G10 –cooled by 14-18K He gas »Modular design and assembly

18. 18 MICE Mtg Oct 2002 Elwyn Baynham RAL Design and Manufacture l Design –design of magnet coils and H2 absorber must be integrated with design of cryostat l Manufacture – the coils are industry standard in terms of conductor/size/stored energy –key issue is cooling and force constraint l field shape gives shear forces in coils –margin of 1.5K is adequate for this type of magnet l operation at the 20% higher field will depend on quality of force support

19. 19 MICE Mtg Oct 2002 Elwyn Baynham RAL Solenoid absorber assembly