Magnetic Measurements of Storage Ring Bending Magnets at ALBA-CELLS J. Campmany on behalf of ID, FE and magnetic measurements section

J. Campmany – ESLS 2008 – Cockcroft Institute2/23 Magnetic Measurements Laboratory Mission of the laboratory: 1.Measurement of Storage Ring Magnets  Measurement of magnetic field maps → Hall probe bench  Measurement of multipoles → Rotating coil bench 2.Construction and measurement of IDs  Permanent magnet blocks characterisation → Helmholtz coils & Fixed Stretched wire  Measurenent of magnetic field maps → Hall probe bench  Measurement of field integrals → Flipping coil bench

J. Campmany – ESLS 2008 – Cockcroft Institute3/23 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

J. Campmany – ESLS 2008 – Cockcroft Institute4/23 Magnetic Measurements Laboratory General view of the laboratory:

J. Campmany – ESLS 2008 – Cockcroft Institute5/23 Characteristics of existing bench: –Longitudinal scanning range: 3 meters –2D Hall probe (only two Hall sensors) –EPICS control system –Point-to-point measurement mode Improvements implemented: –3D 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 Hall probe bench z-axis x-axis y-axis Hall probe Scanning volume: ( ¢x £ ¢y £ ¢z )= 500 £ 250 £ 3000 mm 3 Calibration system: –Dipole Magnet GMW MM –Power supply Danfysik 858 –RMN magnetometer Metrolab PT 2025 –Fluxgate magnetometer Bartington Mag-01 Aig gap of magnet: 15mm 5 NMR probes: |B|= 500 Gauss–2.1 T Fluxgate probe: |B|< 150 Gauss

J. Campmany – ESLS 2008 – Cockcroft Institute6/23 Control system has been migrated from EPICS to TANGO New devices have been included (additional voltmeter for 3 rd Hall sensor, fluxgate magnetometer…) On-the-fly measurement mode has been implemented New TANGO control system Hardware architecture Hall voltage reading Hall probe T control room temperature monitoring Calibration system Motion controller Hall probe current source

J. Campmany – ESLS 2008 – Cockcroft Institute7/23 GUI screenshots New TANGO control system point-to-point application on-the-fly application

J. Campmany – ESLS 2008 – Cockcroft Institute8/23 F.W. Bell Hall sensors Detail of Hall probe circuit board: 3D Hall probe z-sensorx-sensory-sensor 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 Piece breakdown of Hall probe Holder: 4 mm 153 mm probe holder (brass) coupling to movable arm (aluminum) probe circuit board electrical connector movable arm (brass) Hall sensors manganine heater

J. Campmany – ESLS 2008 – Cockcroft Institute9/23 The response of each probe to an external field assumes that the relevant terms in the range T are: where... 3D field calibration method F. Bergsma, «Calibration of hall sensors in three dimensions», 13 th IMMW, May 19-22, 2003, Stanford F. Bergsma «Progress on the 3D calibration of hall probes», 14 th IMMW, Sep 26-29, 2005, Geneva

J. Campmany – ESLS 2008 – Cockcroft Institute10/23 3D 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: BzBz ByBy BxBx (vertical) (horizontal) (longitudinal) a

J. Campmany – ESLS 2008 – Cockcroft Institute11/23 3D field calibration method Jordi Marcos, «Calibration of a 3-axes Hall probe», CELLS internal note ACD-LAIDHall-A-0003.pdf Available from:

J. Campmany – ESLS 2008 – Cockcroft Institute12/23 3D 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 1 Position 2 90º Position 1: magnetic field along vertical (y) direction Position 2: magnetic field along horizontal (x) direction Positions 3 and 4 are defined by Bakelite pieces inserted into the gap of the calibration dipole Side view 13.5º 5º pos. 4 pos. 3 z y Top view pos. 4 pos. 3 30º z y position 3 position 4 Position 3: magnetic field along vertical and longitudinal (y and z) directions Position 4: all three components (x, y and z) non-zero,,ºº

J. Campmany – ESLS 2008 – Cockcroft Institute13/23 Reconstruction of the magnetic field Given the signals of the three sensors (V a, V b and V c ) 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 offsets Systematic measurement of Hall probes temperature (±0.01 ºC)

J. Campmany – ESLS 2008 – Cockcroft Institute14/23 On-the-fly measurement mode Characteristics of on-the-fly measurement mode: –Maximum velocityv z = 18 mm/sec –Minimum step size D z = 20 μm –Min. “dead time” between acquisitions D td = 6 msec –Max. number points/scan30,000 Performance of on-the-fly measurement mode: (when measuring a periodic device with 10 3 Gauss peak field) –Repeatability between different scans ~0.05 mT (0.5 Gauss) rms –Agreement between point-to-point and on-the-fly measurement ~0.05 mT (0.5 Gauss) rms

J. Campmany – ESLS 2008 – Cockcroft Institute15/23 rms difference ~10 -5 T·m (10 G·cm) Comparison of field integral measured using flipping coil and determined using Hall probe for a straight magnetic array vertical I y horizontal I x Performance of Hall probe bench Absolute accuracy of Hall probe bench in terms of field: ±0.05 mT

J. Campmany – ESLS 2008 – Cockcroft Institute16/23 Measurement parameters: –Scan range: ¢x £ ¢z = 98mm £ 2000mm –Scan grid: ±x £ ±z =1 mm £ 1 mm –# of points/map:~200,000 points –measurement time ~9 hours Measurement at y =+2mm above mid-plane: Measurement of Storage Ring Bending Magnet (combined function magnet produced by Danfysik) Measurements done by Valentí Massana, Jordi Marcos and Josep Campmany

J. Campmany – ESLS 2008 – Cockcroft Institute17/23 Measurement of Storage Ring Bending Magnet (combined function magnet produced by Danfysik) Measurement at y=0 (mid-plane):

J. Campmany – ESLS 2008 – Cockcroft Institute18/23 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 Transversal distribution of magnetic field with a gradient of 5.63 T/m asnd a sextupole component B’’ = -2.2 T/m2. Within the range of +/- 15 mm no higher multipoles are significative

J. Campmany – ESLS 2008 – Cockcroft Institute19/23 Longitudinal –along the electron trajectory- distribution of the magnetic flux density for the positive and negative halfs of the bending magnet. Measurement of Storage Ring Bending Magnet

J. Campmany – ESLS 2008 – Cockcroft Institute20/23 Longitudinal –along the electron trajectory- distribution of the gradient for the positive and negative halfs of the bending magnet. Measurement of Storage Ring Bending Magnet

J. Campmany – ESLS 2008 – Cockcroft Institute21/23 Measurement of Storage Ring Bending Magnet Longitudinal –along the electron trajectory- distribution of the sextupole for the positive and negative halfs of the bending magnet.

J. Campmany – ESLS 2008 – Cockcroft Institute22/23 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

J. Campmany – ESLS 2008 – Cockcroft Institute23/23 Thank you for your attention

J. Campmany – ESLS 2008 – Cockcroft Institute24/23 Measurements have been applied to sorting Calculations done by Zeus Martí, Beam dynamics section at CELLS, internal report AAD-SRBD-A-0007

J. Campmany – ESLS 2008 – Cockcroft Institute25/23 Reduction of influence of errors Beta beat reduced a factor 4 Phase beat reduced a factor 6