Magnetic Measurements of Storage Ring Bending Magnets at ALBA-CELLS J. Campmany on behalf of ID, FE and magnetic measurements section 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany
Magnetic Measurements Laboratory 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 2
Magnetic Measurements Laboratory Measurement benches 1. Hall probe bench – Partially build in-house 2. Rotating coil bench – Purchased from CERN 3. Flipping coil bench – Purchased from ESRF 4. Fixed stretched wire – Designed and built in-house 5. Helmholtz coils – Purchased from Elettra 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 3
Magnetic Measurements Laboratory General view of the laboratory: 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 4
Hall probe bench Characteristics of existing bench: – Longitudinal scanning range: 3 meters – 2 D Hall probe (only two Hall sensors) – EPICS control system – Point-to-point measurement mode Improvements implemented: – 3 D Hall probe (three Hall sensors) – New probe calibration scheme – Offset determination system – Accurate determination of relative distances between sensors – TANGO control system – On-the-fly measurement mode Calibration system: – – Dipole Magnet GMW 3473 -50 150 MM Power supply Danfysik 858 RMN magnetometer Metrolab PT 2025 Fluxgate magnetometer Bartington Mag-01 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany Scanning volume: (¢x£¢y£¢z)=500£ 250£ 3000 mm 3 Aig gap of magnet: 15 mm 5 NMR probes: |B|= 500 Gauss– 2. 1 T Fluxgate probe: |B|< 150 Gauss 5
New TANGO control system • New devices have been included (additional voltmeter for 3 rd Hall sensor, fluxgate magnetometer…) • On-the-fly measurement mode has been implemented room temperature monitoring Hall probe T control Hall voltage reading • Control system has been migrated from EPICS to TANGO Calibration system Hall probe current source Motion controller Hardware architecture 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 6
New TANGO control system GUI screenshots on-the-fly application point-to-point application 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 7
3 D Hall probe F. W. Bell Hall sensors Piece breakdown of Hall probe Holder: Detail of Hall probe circuit board: Pt-100 (T sensor) space to allocate heater the temperature sensor and the manganine heater, in combination with a PID controller (Eurotherm 3508) allow to control the temperature of the probe within ± 0. 05ºC 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 8
3 D field calibration method The response of each probe to an external field assumes that the relevant terms in the range 0 - 1. 7 T are: where. . . F. Bergsma, «Calibration of hall sensors in three dimensions» , 13 th IMMW, May 19 -22, 2003, Stanford F. Bergsma «Progress on the 3 D calibration of hall probes» , 14 th IMMW, Sep 26 -29, 2005, Geneva 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 9
3 D field calibration method All coefficients except the main (c 10) are assumed to be B independent, and all thermal dependence is assumed to be contained in the linear term c 10: where T 0 is the calibration temperature. Hall sensors are not perfectly aligned with respect to the reference frame: By Bx Bz 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 10
3 D field calibration method Jordi Marcos, «Calibration of a 3 -axes Hall probe» , CELLS internal note ACD-LAIDHall-A-0003. pdf Available from: www. cells. es/Divisions/Accelerators/Insertion_Devices/ID-laboratory/Hall_probe_bench/ 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 11
3 D field calibration method Field calibration carried out at four predefined positions: At positions 1 and 2 the probe is attached to the moving arm Position 2 Position 1: magnetic field along vertical (y) direction 90º Position 2: magnetic field along horizontal (x) direction Top view 30º pos. 4 Positions 3 and 4 are defined by Bakelite pieces inserted into the gap of the calibration dipole pos. 3 Position 3: magnetic field along vertical and longitudinal (y and z) directions position 4 Side view 5º 13. 5º pos. 4 Position 4: all three components (x, y and z) non-zero pos. 3 position 3 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 12
Reconstruction of the magnetic field Given the signals of the three sensors (Va, Vb and Vc) and the temperature of the probe (T), the three components of the magnetic field are determined by inverting the non-linear system (it is done by means of a C routine implementing Broydn method): Systematic measurement of Hall probes temperature (± 0. 01 ºC) 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany Systematic measurement of offsets 13
On-the-fly measurement mode 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 14
Performance of Hall probe bench Absolute accuracy of Hall probe bench in terms of field: ± 0. 05 m. T Comparison of field integral measured using flipping coil and determined using Hall probe for a straight magnetic array rms difference ~10 -5 T·m (10 G·cm) 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 15
Measurement of Storage Ring Bending Magnet Measurement at y=+2 mm above mid-plane: (combined function magnet produced by Danfysik) Measurement parameters: – Scan range: ¢x£¢z = 98 mm £ 2000 mm – Scan grid: ±x£±z =1 mm £ 1 mm – # of points/map: ~200, 000 points – measurement time ~9 hours Measurements done by Valentí Massana, Jordi Marcos and Josep Campmany 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 16
Measurement of Storage Ring Bending Magnet (combined function magnet produced by Danfysik) Measurement at y=0 (mid-plane): 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 17
Measurement of Storage Ring Bending Magnet Normalized excitation curve (B/I) = (N*μ/gap) as a function of the excitation current. Saturation happens for currents above 500 A 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany Transversal distribution of magnetic field with a gradient of 5. 63 T/m asnd a sextupole component B’’ = -2. 2 T/m 2. Within the range of +/- 15 mm no higher multipoles are significative 18
Measurement of Storage Ring Bending Magnet 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 19
Measurement of Storage Ring Bending Magnet 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 20
Measurement of Storage Ring Bending Magnet 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 21
Reduction of influence of errors Closed orbit distortion reduced a factor 10 Calculations done by Zeus Martí, Beam dynamics section at CELLS, internal report AAD-SRBD-A-0007 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 22
Thank you for your attention 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 23
Measurements have been applied to sorting Calculations done by Zeus Martí, Beam dynamics section at CELLS, internal report AAD-SRBD-A-0007 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany 24
Reduction of influence of errors Beta beat reduced a factor 4 27 -28. 11. 2008 – ESLS 2008 – Cockcroft Institute J. Campmany Phase beat reduced a factor 6 25
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