Analysis of MBXW and MBW Per Hagen (TE/MSC) 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 ( 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 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 All 4 measurements of MBXW 1 Modest, flat “resmag” around 30, 40A Geo-gamma 100A RC with 50 units less saturation

7 Statistics of 3 RC measurementsStatistics 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 1 st 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 I_geo_gamma vanishes Use the 2 “calibrated” values for TF 30, 40 A Used for FIDEL resmag fit

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

10 MBXW TF REFPARM and fit error Conclusion: Resmag only essential difference!

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

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

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

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

15 MBW TF REFPARM and fit error Conclusion: Resmag only essential difference!

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