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Talk outline

Talk outline. 1 st talk: Magnetic forces Quench in the absorber cryostat 2 nd talk: Shielding of magnetic fringe fields. MICE Magnetic forces and quench issues. Elwyn Baynham James Rochford. MICE Meeting Berkley December 2003. Magnet and quench issues. Look at two topics

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Talk outline

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  1. Talk outline • 1st talk: • Magnetic forces • Quench in the absorber cryostat • 2nd talk: • Shielding of magnetic fringe fields

  2. MICE Magnetic forces and quench issues Elwyn Baynham James Rochford MICE Meeting Berkley December 2003

  3. Magnet and quench issues • Look at two topics • Magnetic forces • Containment of normal operational forces • Imbalance in normal forces following a quench • Quench in the absorber cryostat • Forces in absorber windows • Power dissipation in hydrogen

  4. Containment of forces in normal Operation Force restraint Between cryostats Coupling coil Detector cryostat For Flip mode 240MeV/c,b=43cm Suspension (transferring nett internal force) 261 T 310 T Internal force restraint Nett 49T (Forces shown for outer most pair of flip coils) LH

  5. Containment of forces in normal Operation Force restraint Between cryostats Coupling coil module Detector cryostat For Non Flip mode 240MeV/c,b=7cm Suspension (transferring nett internal force) 208 T 157 T Internal force restraint Nett 51 T (Forces shown for outer most pair of flip coils) LH

  6. Containment of forces in normal Operation • Normal operation - summary • Internal forces 250-300Tonnes • Contained within the magnet former • Any nett force transferred to warm cryostat • Hydrogen system independent sees no force • Inter cryostat forces 50-100 Tonnes • Transferred between cryostats • No nett force over complete channel

  7. 490 131 719 128 719 128 490 131 794 794 75 75 3 3 Magnet Quench - force imbalance Inter cryostat force Quench in all focusing pairs Changes in forces For Flip mode 240MeV/c,b=43cm(all forces in KN)

  8. 490 792 131 719 795 792 719 795 490 131 Magnet Quench - force imbalance Quench in coupling pair Inter cryostat force Changes in forces 76 302 30 76 For Flip mode 240MeV/c,b=43cm(all forces in KN)

  9. 490 490 131 719 305 136 212 719 719 490 131 795 0 0 5 Magnet Quench - force imbalance Loss of detector coils Inter cryostat force Changes in forces For Flip mode 240MeV/c,b=43cm(all forces in KN)

  10. Magnet Quench - force imbalance • Quench imbalance summary • During a quench imbalanced forces • Experience big change in forces • Change of direction • Magnitudes comparable to normal operation • Conclusion • Imbalance forces do not need any special considerations and are readily contained in normal design

  11. Focus coil quench internal effects • Effects of a Quench in the focus coil module • 2d and 3d finite element models • Eddy currents • Forces on thin windows • Power dissipated in the hydrogen

  12. Focus coil quench internal effects S.steel 128 A/mm2 Al6061 Effective window thickness Al6061 Teff 1mm 2d Quench model Teff 0.2mm

  13. Focus coil quench internal effects Current rundown during a quench for 51H with no protection resistance

  14. Focus coil quench internal effects Peak currents Eddy current distribution in absorber windows in flip mode Eddy current distribution in holders and windows 2s into a quench whilst operating in 240MeV/C,Beta=43cm mode

  15. Focus coil quench internal effects ~10J dissipated in the Hydrogen Not a problem Power dissipated in the inner vessel windows during a quench in 240MeV/C,Beta=43cmm mode

  16. Focus coil quench internal effects ~15KJ dissipated in the Hydrogen For hydrogen 18k S.heat 8305 J/kgK Its effect is to raise the temperature of the liquid from 18K to 19.8k Power dissipated in the inner vessel bodies during a quench in 240MeV/C,Beta=43cmm mode

  17. Focus coil quench internal effects Atmospheric pressure 1x105Nm2 Force on window ~8KN Force on the inner vessel windows during a quench in 240MeV/C,Beta=43cm mode

  18. Focus coil quench internal effects Using expression We can estimate the peak stress in the window Note the max yield strength for AL6061 is 273MPa. This is 10 times less than the peak stress seen in the windows

  19. Focus coil quench internal effects What is the effect of an offset absorber ? Absorber vessel moved by 5mm axially Model changed to look at the effect of offsetting the absorber axially

  20. Focus coil quench internal effects Force on the Absorber vessel body during a quench in 240MeV/C,Beta=43cm mode with the vessels offset axially by 5mm

  21. Focus coil quench internal effects Eddy current distribution in windows for Solenoid mode Eddy current distribution in holders and windows 2s into a quench whilst operating in solenoid mode -240MeV/C,Beta=7cm

  22. Focus coil quench internal effects ~40J dissipated in the Hydrogen Not a problem Power dissipated in the inner vessel windows during a quench for solenoid mode -240MeV/C,Beta=7cm

  23. Focus coil quench internal effects • ~36KJ dissipated in the • Hydrogen • For hydrogen 18k • S.heat 8305 J/kgK • Its effect is to raise the temperature of the liquid from 18K to 22.3k • Vapour pressure 1.6Bar • Pessimistic • Solid absorber body • Heat capacity for 18k • 240MeV/c • Still just acceptable Power dissipated in the inner vessel bodies during a quench for solenoid mode -240MeV/C,Beta=7cm

  24. Focus coil quench internal effects Atmospheric pressure 1x105Nm2 Force on window ~8KN Force on the inner vessel windows during a quench for solenoid mode -240MeV/C,Beta=7cm

  25. Focus coil quench internal effects • Focus coil quench summary • Forces during a quench • Looked at worst possible cases • Small, 100’sN - much less than normal vacuum force • Eddy current distribution concentrated in outer window • Peak stress here of order 22MPa much less than yield stress 250MPa • Power dissipation • Worst solenoid mode 240MeV/c-36kJ • Enough to raise the vapour pressure to 1.6Bar • This easily contained in hydrogen system

  26. END

  27. MICE Coils magnetic shielding James Rochford Iouri Ivaniouchenkov MICE Meeting Berkley December 2003

  28. Shielding Requirements • Areas with public access The stray field must be below 5 gauss in these regions • Areas occupied by detectors The stray field at the ends of the magnetic channel must be low enough for the TOF Cerenkov and calorimetric detectors to operate.

  29. Shielding Requirements Areas with public access

  30. 3d models • Main shield Open ended rectangular box model 20mm thick iron plate • length +/-8.5m • Coils offset • Detector shield 50mm thick iron plate ID 40mm OD 1.8m 6m 2m 17m 6.5m 3.8m

  31. Model results For flip mode 200Mev/c, beta 43cm Fringe field on outer walls 5gauss contour

  32. Model results forSolenoid mode200MeV/c,beta=7cm The proposed simple 20mm box shield is inadequate to shield the ISIS\MICE control rooms Field on wall surface peaks at 32 gauss Field on wall surface peaks at 72 gauss

  33. Shielding summary • Have shown the simple box shield is adequate for normal operation at 200mev/c. • This will also be ok for the 240Mev/c case. • The simple shield is not sufficient to shield solenoid mode. • As it stands the proposed shield will need some modifications to accommodate solenoid mode • Increase thickness • Multiple layers • Close ends

  34. END

  35. 490 128 719 131 719 131 490 128 794 794 75 75 3 3 Magnet Quench - force imbalance 334 3099 131 2653 131 64 1417 3099 334 1417 64 392 2609 2653 2609 392 91 91 Inter cryostat force Quench in all focusing pairs Changes in forces For Flip mode 240MeV/c,b=43cm(all forces in KN)

  36. 334 3099 131 2653 131 64 1417 3099 334 1417 64 392 2609 2653 2609 392 91 91 792 490 131 719 795 795 490 131 719 792 Magnet Quench - force imbalance Quench in coupling pair Inter cryostat force Changes in forces 76 302 30 76 For Flip mode 240MeV/c,b=43cm(all forces in KN)

  37. 334 3099 131 2653 131 64 1417 3099 334 1417 64 392 2609 2653 2609 392 91 91 490 490 131 719 136 305 719 719 212 490 131 795 0 0 5 Magnet Quench - force imbalance Loss of detector coils Inter cryostat force Changes in forces For Flip mode 240MeV/c,b=43cm(all forces in KN)

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