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Analysis of MBXW and MBW

Analysis of MBXW and MBW. Per Hagen (TE/MSC) 29.09.2009. Acknowledgements: R. Wolf (2008 analysis), G. de Rijk (ROXIE model), B. Auchmann (ROXIE support), E. Todesco (discussions ), BINP (Novosibirsk) and CERN personnel involved in measurements. Function in LHC.

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Analysis of MBXW and MBW

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  1. Analysis of MBXW and MBW Per Hagen (TE/MSC) 29.09.2009 Acknowledgements: R. Wolf (2008 analysis), G. de Rijk (ROXIE model), B. Auchmann (ROXIE support), E. Todesco (discussions), BINP (Novosibirsk) and CERN personnel involved in measurements

  2. Function in LHC • Classical NC-magnets needed where SC-magnets would quench due to radiation • MBXW (2 beams in one aperture) are used for separating / combining the beams in ATLAS and CMS (194 – 224) mm. 6 MBXW = optics element D1. MBXW=29. • MBW (2 separate apertures) are used for changing the beam separation (194-224 mm) in cleaning regions where we have collimators (IR3, IR7). IR3: 3 MBW = optics elements D4 + D3. IR2: 2 MBW = D4 + D3. MBW=24. • Designed by CERN. Produced by BINP (Budker Institute of Nuclear Physics) MBXW MBW

  3. CERN > 5000 KM BINP

  4. Measurements • First magnet measured with NMR for absolute calibration • Each magnet measured at BINP with HALL probe array • 19 probes along horizontal axis • Calibrated with NMR* measurement to give the B*L integral • Longitudinal scan step: 2 cm • MBXW aperture measured: ± 45 mm • MBW each aperture measured: range ± 60 to ± 148 mm (center 194 mm sep = 97 mm, 224 mm = 112 mm) • FiDeL REFPARM: Use only BL from center of each aperture Could have taken actual slot into account (center of beam as function of s) • Rotating coil measurements after delivery to CERN giving B(I) and harmonics in central position: MBXW 1, 9, 20 + MBW 1, 9, 15 * NMR = Nuclear Magnetic Resonance. Constant magnetic field affects nuclear E + spin states. Measure wavelength of emitted photons in measuring device which is scales with B field.

  5. How results are presented • Geo-gamma @ 100 A is removed • All data points converted to units of geo-gamma • Why? Compare and fit shapes of B(I), BL(I) curves Facts • We use only the FIDEL residual magnetisation and saturation components for the “warm” magnets • Assume local B(I) curves from “middle of magnet” have same shape as BL(I) curves • LHC operational ranges: MBXW 41 to 643 A (0.08 – 1.3 T) MBW 43 to 685 A (0.08 – 1.3 T)

  6. MBXW TF Modest, flat “resmag” around 30, 40A Geo-gamma 100A RC with 50 units less saturation All 4 measurements of MBXW 1

  7. Statistics of 3 RC measurements Statistics of 29 HALL measurements Individual geo-gamma per circuit Conclusion:Less difference in saturation RC wrt HALL!

  8. MBXW resmag (2009 feature) • The RC measurements include measurement of remanent field at 0 A as 1st measurement after pre-cycles to stabilise B(I) curve, B(0) = 10 G • Assume TF(I) at low current given by “geometric” + remanent allows to make an initial resmag table (expressed in units of geometric) • Assume remanent field measurement contains an absolute error, and the condition that resmag @ I_geo_gamma vanishes • Use the 2 “calibrated” values for TF fit @ 30, 40 A Used for FIDEL resmag fit

  9. MBXW TF fit based on residual magnetization ROXIE has much less saturation FIDEL fit where HALL measurements given more weight

  10. MBXW TF REFPARM and fit error 2009 Conclusion:Resmag only essentialdifference! 2008

  11. MBXW harmonics (3 magnets) Conclusion:Only b2 visible but -0.2 units is too small and uncertain for REFPARM

  12. MBW TF Modest “resmag” around 30, 40A Geo-gamma 100A All measurements of MBW 1 All 4 measurements of MBW 1 12

  13. Statistics of 2x3 RC measurements Statistics of 24 HALL measurements Individual geo-gamma per circuit Conclusion:RC always less saturation similar to MBXW Conclusion from HALL:No difference between apertures 13

  14. MBW TF fit Based on residual magnetization like for MBXW FIDEL fit where HALL measurements given more weight 14

  15. MBW TF REFPARM and fit error 2009 2008 Conclusion:Resmag only essentialdifference! 15

  16. MBW harmonics (3 magnets) Conclusion:Use geometric for b3, b5, b7 same sign both apertures 16

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