CERN –GSI/CEA MM preparation meeting, Magnetic Measurements WP

CERN –GSI/CEA MM preparation meeting, Dipoles Translating coils 2 ΔBΔB ΔsΔs ξ The flux measured from the absolute coil is the convolution of the field profile and a rectangular function. The integral over f*g is equal to the product of the integrals f and g

CERN –GSI/CEA MM preparation meeting, Dipoles 3 Measurement system - Translating fluxmeter with 12 coils - Speed min 0.1 m/s - Magnet ramp rate 120 sec from 0 to Imax - Eddy current stabilization time 60 sec (to be verified on the pre-series) - Support tables installed and aligned during the cool down - 3 vertical levels - 5 current plateaus Total number of dipoles: 24

CERN –GSI/CEA MM preparation meeting, Dipoles 4 Measurement time (Series tests) ParameterRequirementsTime Instrument configuration and check 10 days 1 day Pre-cycling3 pre-cycles (480 sec min duration each) total ~0.13 days Cycling (5 plateaus from Imin to Imax)0.08 days (times 3 vertical levels) Displacement next vertical level0.12 days (times 3 vertical levels) Next measurement cycling configuration0.03 days (times 3 vertical levels) Data analysis1.5 days (to be done at cold in case measurements should be repeated) Relative calibration (1 times per month) in the magnet under test 2 days Absolute calibration (1 per month?) in the magnet under test 2 days Total8 days

CERN –GSI/CEA MM preparation meeting, Dipoles 5 Field Quality 3 longitudinal parts Absolute integral field required accuracy+ 5*10 -4 Integral field homogeneity required accuracy+ 5*10 -5 Definitions: - Homogeneity definition (should the gradient be considered in here)? - Measurement path in the longitudinal direction (hard edge or parabolic path?) - Path length (4000 mm) can it be reduced for series tests (provided that the full map will give the information about the whole fringe field) - Measurement report (passport with checklist ok/not ok, database with field homogeneity, etc.) - The B L reference value? - Measurement of B 0 - How the measured field homogeneity will be treated? - Polarity convention of homogeneity measurements due to the different configurations of the measurement benches

CERN –GSI/CEA MM preparation meeting, Dipoles 6 Field Quality 3 longitudinal parts Absolute integral field required accuracy+ 5*10 -4 Integral field homogeneity required accuracy+ 5*10 -5 Practical aspects: - M2M reproducibility: measurement hall not thermally stabilized, is it enough to provide measurements of the yoke temperature? - Is it foreseen to have an hall probe (or any other monitor sensor) during the magnet operation? - Position of fiducials: How are the fiducials related w.r.t. the pole surface (mechanical measurement, absolute positioning w.r.t. lamination?) and who will provide these measurements - Tolerances on the cryostat installation? (access to the pole surface)

CERN –GSI/CEA MM preparation meeting, Dipoles 7  Extended measurement program for the pre-series Open questions: - Is it not foreseen to test the variation of a local measurement w.r.t. the integral measurement? - Is the measurement platform foreseen to have access to the straight section of the magnet? - Is it possible to dismount half yoke of the magnet in the build. 180 and reassembly it ? - Total scan length? - Is it foreseen to shim to adjust the magnetic length or the homogeneity of the pre-series magnet ? Full map with 3D hall probe at 3 currents and 3 planes of: - One dipole unit per type (2 + 1) - All dipoles with (straight) exit for beam (2 +[1]) - Yoke assembly reproducibility test

CERN –GSI/CEA MM preparation meeting, Multiplets 8 ParametersRequirements Length of the measurements path2320 mm (short quads) 2720 mm (long quads) Aperture radius (mm)190 Good Field region radius (mm)180 Angle (mrad)<0.5 Axis (mm) except steerers0.2 Quads Current levels5 Integral field homogeneity+ 5*10 -5 Multiplets Absolute integral field accuracy+ 1*10 -3 Integral field homogeneity+ 2*10 -4  Series test requirements

CERN –GSI/CEA MM preparation meeting,  Rotating coil 9 Magnetic measurements proposal of the FAIR magnets  Reference radius 180 mm  Maximum weight of the shaft 60 Kg  Measurement integral length 3 m  MRU inside the aperture 3m 0.01 m 220 mm diameter

CERN –GSI/CEA MM preparation meeting, Multiplets Time costsdays Installation SSW, check and positioning1 Pre-cycling for 1 magnet0.13 Measurement cycle 5 level (Gdl (x,y) and roll)0.08 Fiducialize0.06 Connection next magnet0.12 Remove Wire, install shaft1 Pre-cycling for 1 magnet0.13 Positioning shaft0.01 Measurement cycle 5 levels0.08 Connection next magnet0.12 Analysis2 Worst case to be repeated 7 times (not for steerers): 2.73 days Total time 10 days No margin or contingencies for other operations. Evaluate the hypothesis to go down to 3 current levels Worst case to be repeated 9 times (not for steerers): 3 days  Series test requirements

CERN –GSI/CEA MM preparation meeting,  extended pre-series tests Multiplets Full map with a short coil at 10 mm steps of: - 1 long quad - 1 short quad - 1 sextupole - How many current levels? - Is it foreseen to shim to adjust the magnetic length or the homogeneity of the pre-series magnet ? Cross-check measurements - Cross-check of the field homogeneity with another system (a standard shaft at a smaller radius). - Cross-check measurements of the axis measurement performed with the SSW with another system (vibrating wire) - Integral field - integral transfer function - hysteresis and Homogeneity at 16 current levels

CERN –GSI/CEA MM preparation meeting,  extended pre-series tests Multiplets Open questions: - Will the local harmonics be used in particle tracking codes? - How is defined the polarity of the magnet w.r.t. the cryostat? (on the benches is possible to install the multiplet with different orientation) - If the magnets have different optical function in the machine are we measuring in the same configuration or in the final powering mode of the machine? - Should we measure the longitudinal magnetic centre?

CERN –GSI/CEA MM preparation meeting,  Rotating coil Multiplets Open questions: - Tangential or radial coil - Calibration / pcb coils - Measurements radius - Coil length

CERN –GSI/CEA MM preparation meeting,  Rotating coil 14 Multiplets  Tangential  N turns = 64  Surface absolute coil = 3.64 m 2  L = 3 m  Width = 38 mm  (for the main quad) Output ~5 1Hz for the absolute at I nom  Coil sensitivity up to 15 th order reduced by a third for a measurement radius of 175 mm  the coil sensitivity is close to zero around the 50 th harmonic  Still possible to extrapolate the harmonics to R=180 mm

CERN –GSI/CEA MM preparation meeting,  Rotating coil 15 Multiplets  Radial coil  N = 128  Surface absolute coil = 3.84 m 2  L = 3 m  Width = 10 mm  (for the main quad) Output ~5 1Hz for the absolute at I nom  Coil sensitivity up to 15 th order reduced by a third for a measurement radius of 175 mm  Still possible to extrapolate the harmonics to R=180 mm

CERN –GSI/CEA MM preparation meeting,  Rotating coil 16 Multiplets  Radial coil (PCB)  N = 60 (10 Turns * 6 Layers)  Surface absolute coil = 1.26 m 2  L = 2* 1.5 m  Width = 7 mm  (for the main quad) Output ~1.5 1Hz for the absolute at I nom  measurement radius of 170 mm  PRO No need for surface calibration Very good compensation (~ 5000) weight  CONS Cost assembly Mechanical stability

CERN –GSI/CEA MM preparation meeting, Multiplets 17 Shaft length - The one segment shaft with a fix rallonge can be used for all the multiplets (included the not standard) and to scan the longitudinal multipoles. - 3 m coils difficult winding and almost impossible to calibrate Reduce coil length2 segments of ~ 1.5 m (standard winding or PCB) PCB boards no need of relative calibration Reduce requirements on absolute accuracy (rely on design) Only radial scheme and reduce measurement radius to 170 mm Increase measurement time (long quads measured with more than 1 measurements) Increase system complexity Reduce the measurement radius to allow in situ calibration of absolute coil radius

CERN –GSI/CEA MM preparation meeting, Multiplets Rotating coil: conclusions Reduce the measurements radius to 170 mm does not affect largely the coil sensitivity up to the 15 th order A PCB coils shaft need only absolute calibration that could be done in situ w.r.t. a stretched wire measurements. For the relative calibration is possible to rely on the accuracy of the PCB board. In any case we need some margin on the shaft radius if we would calibrate in situ the shaft. 5% reduction of the measurement radius still allows extrapolation with a not large impact on the accuracy