1. Eddy current modelling for ILC target ILC meeting 31 st Jan- 3 rd Feb 2007 IHEP-Beijing James Rochford

2. Modelling ILC target Short talk on eddy current modelling of ILC disk Outline: Electra modelling of LLB rotating disk experiment –To build confidence in Electra code Use Electra to model the ILC wheel

3. Rotating disk experiment Used some optimiser code to develop a model of experimental permanent magnet

4. Rotating disk experiment Final field match for experimental permanent magnet Good match to field data

5. Rotating disk experiment Electra model of copper disk Permament magnet ‘NdFeB’ properties defined from optimiser fit Variable magnet gap Conductor – initial model copper 1.68e-8Ωm

6. Rotating disk experiment Eddy currents A/mm 2 @2000rpm Unit vectors

7. Initial model results for gap 0.254mm Rotating disk experiment Conductivity of disk not measured blue curve - high cond copper Red curve 0.75 times high cond copper Fit dependant of conductivity of copper used

8. Final model results for all gap spacing's Rotating disk experiment Models use 0.75 times conductivity of high cond copper

9. Final model results for all gap spacing's Rotating disk experiment Models use 0.75 times conductivity of high cond copper

10. ILC wheel model Wheel parameters Wheel dia: 2m Axial thickness: 14mm Radial thickness: 50mm Material: Ti alloy Focusing solenoids Upstream: Outer radius 540mm Inner radius 225mm Axial length 250mm Axial offset from wheel centre 100mm Jden 46A/mm 2 Downstream: Outer radius 400mm Inner radius 225mm Axial length 50mm Axial offset from wheel centre 100mm Jden 46A/mm2 Ti alloy Ti6Al4V 1.08e-6Ωm

11. ILC wheel model Field from focusing solenoids Axis field Bz

12. ILC wheel model Mesh distribution in wheel Optimised to model eddy currents in wheel Will need to add higher mesh density on coil axis to improve field modelling here

13. ILC wheel model Eddys @ 2000rpm

14. ILC wheel model Power required to drive wheel @ different rotational speeds Integrate power dissipation in wheel volume directly in model –I 2 r Model-torque calculated use this to calc power provided by braking force Should be equivalent The large power required to drive the wheel may pose a problem in the design.

15. ILC wheel model Electra model of cu disk good agreement with expt Started to model ILC wheel How to proceed? Need some directions here Look at 1m wheel Look at field effects on 2 m version Modelling a pulsed system …….?