IMMW12 Grenoble Oct 2001 Final Version of Magnetic axis measurement device in Industry Aznar S., Billan J., Fischer F., Galbraith P., Garcia-Perez J., Goy S., Mermillod N., Peiro G., Patti G., Rathjen C. CERN
Overview Measurement Principle Instruments + LTD Mole positioning system & measurement Mechanical and Magnetic axis measurement Calibration system & method Optical mole Performance Axis measurements performance Results from prototypes and preseries Conclusions
Measurement principle Measure the offset between cold bore tube axis (geometry for assembling) and magnet axis (QCD for dipole) LTD retroreflector for X,Y, Z in space (Leica measurement) => cold bore axis 4 * 100 mm fixed tangential coils => local magnetic offset w.r.t. old bore axis 0.5 Amps AC current at 25 Hz for synchronous detection of induced current Cold bore position w.r.t. mole: mechanical autocentring or LED s measure (cold bore diameter and its centre)
Instruments 2 mole versions (global mechanic & global optic) global mechanic, auto centring and ballast for level global optic, LED s and motorised levelling LTD 500 Leica for 3D mole position measurement Synchronous detection electronics and positioning (angular and longitudinal) motors Software: AXYZ and Labview
Coldbore CD Cornercube Lase LED rbeam LED Mole Cornercube Optic Mole
Sensitivity & Frequency check Axis Measurement vs QCD Frequency (O2, T2) Horizontal (mm) Vertical (mm) 0.34 0.32 Axis measurement 0.30 0.28 0.26 0.24 0.22 0.20 0 10 20 30 40 50 Frequency (Hz)
Sextupole calibration residuals 10 Horizontal Vertical 10 8 8 6 6 4 4 2 2 0 0-2 -2-4 -4-6 -6-8 -8-10 -1.0-0.8-0.6-0.4-0.2 0.0 0.2 0.4 0.6 0.8 1.0-10
Repeatability of diameter measurement 0.015 0.010 diameter repeatability [mm] 0.005 0.000-0.005-0.010-0.015 0 1000 2000 3000 4000 5000 6000 7000 8000 longitudinal coordinate [mm]
Calibration method We aim to have the three key centres, namely: Reflector centre Centre of gravity of search coils Cold bore tube centre (Centring of mechanical mole fingers or Centring of LED s) well aligned, starting with the best mechanical precision from fabrication, but there are limits to that. In reality we have offsets between these centres. So we try to measure them. For that we use the following ingredients: turning by 180 in a 50 mm calibrated tubes turning by 180 in a calibrated quadrupole displacing transversally the mole inside a 50 mm tube to calibrate the LED s behaviour special device to calibrate the mechanical mole fingers
Calibration bench
Calibration method 180 º rotations 1 3 4 2 2 4 3 1
Optical Mole (Calibration) 4 Displacement of etalon in horizontal direction led 2 led 4 Measured displacement 0.102 Deviation from reference circle [µ m] 3 2 1 0-1 -2-3 0.101 0.101 0.100 0.100 0.099 0.099 0.098 Measured displacement [mm] -4 0.098-1.5-1 -0.5 0 0.5 1 1.5 Displacement [mm]
Magnet Axis measurements Preserie O1-Magnetic Offset Repeatibility (external tube, vertical offset) Preserie before End Cover Collared Coil Preserie final 0.2 0.15 0.1 Magnetic offset [mm] 0.05 0-0.05-0.1-0.15 0 2 4 6 8 10 12 14 Length s [m]
Magnet Axis measurements NOELL1 - Horizontal FITTED 3.5 1.5 3.0 1.0 2.5 0.5 2.0 0.0 1.5-0.5 Offset (mm) 1.0 0.5-1.0-1.5 Offset (mm) 0.0-2.0-0.5-2.5-1.0-3.0-1.5 0 2 4 6 8 10 12 14 16-3.5 longitudinal coordinate (m) Y mech Inner Tube Y mag Inner Tube Y mech Outer Tube Ymag Outer Tube
Magnet Axis measurements NOELL1 - Vertical FITTED 3.5 1.5 3.0 1.0 2.5 0.5 2.0 0.0 Offset (mm) 1.5 1.0 0.5-0.5-1.0-1.5 Offset (mm) 0.0-2.0-0.5-2.5-1.0-3.0-1.5 0 2 4 6 8 10 12 14 16 Longitudinal coordinate (m) -3.5 Z mech Inner Tube Zmag Inner Tube Z mech Outer Tube Zmag Outer Tube
Results from prototypes and preseries
Conclusions We can measure the Magnetic axis of dipoles and correctors of LHC magnet with good accuracy, 0.03 mm in a very short time in parallel with the Mechanical axis measurements The Optical mole gives the diameter measurement The calibration bench and method are ready The results show a good agreement between both Magnetic and Mechanical axis