Development of a Rogowski coil as a new Beam Position Monitor (BPM) - PowerPoint PPT Presentation

Development of a Rogowski coil as a new Beam Position Monitor (BPM) Mitglied der Helmholtz-Gemeinschaft Horizontal and Vertical Rogowski BPM Fabian Trinkel for the JEDI collaboration Eucard Workshop Mainz 2015

Content • Introduction • Theory for positon determination with a Rogowski coil as BPM • Technical approach • First measurements with a Rogowski coil as horizontal BPM • Summary and outlook Mitglied der Helmholtz-Gemeinschaft 28 September 2015 2

Introduction Existence of an EDM violates CP-theorem, which is necessary to explain the matter over antimatter dominance in the Universe 𝑇 𝑇 ℋ = −𝜈 𝑇 ∙ 𝐶 − 𝑒 𝑇 ∙ 𝐹 𝑇 𝑇 𝑸 : ℋ = −𝜈 𝑇 ∙ 𝐶 + 𝑒 𝑇 ∙ 𝑭 𝑇 𝑇 𝑼 : ℋ = −𝜈 𝑇 ∙ 𝐶 + 𝑒 𝑇 ∙ 𝑭  : MDM Standard Model EDM prediction: 10 −32 to 10 −31 𝑓𝑑𝑛 𝒆 : EDM Mitglied der Helmholtz-Gemeinschaft Aim of Jülich Electric Dipole moment Investigations collaboration: Measure the EDM of charged hadrons for protons p and deuterons d 28 September 2015 3

EDM measurements in storage rings 𝑒𝑇 × 𝐹 𝑒𝑢∝ 𝑒 = 𝜃 2⋅ 𝑓 𝑒 2𝑛𝑑𝑇 General idea: • Inject polarised particles with spin pointing towards the momentum direction • “Frozen Spin” -Technique: without EDM spin stays aligned to momentum • EDM couples to electric bending fields Mitglied der Helmholtz-Gemeinschaft • EDM leads to a polarization build-up in vertical direction Challenge: Control of the Orbit with a very high accuracy to prevent systematic effects 28 September 2015 4

Cooler Synchrotron COSY in Jülich Sextupole magnets RF Devices for Spin Manipulations Electron Cooler Installation of the EDDA Polarimeter Rogowski Coil in a Chamber Mitglied der Helmholtz-Gemeinschaft Momentum up to 3.5 GeV/c Polarized Protons / Deuterons Circumference 184 m 28. September 2015 5

Beam Position Monitor (BPM) BPM measures transverse beam positon ( 𝑦 0 , 𝑧 0 ) Electrostatic BPM (Standard at COSY): Magnetostatic BPM (New Development): Length ≈ 20 cm Length ≈ 1 cm Excellent response to an RF signal Easy to manufacture Mitglied der Helmholtz-Gemeinschaft Accuracy of the existing COSY BPM More precise position measurement with system ≈ 0.1 mm Rogowski BPM System and a first step to Not enough for an EDM measurement a SQUID-based BPM development 28 September 2015 6

Rogowski Coil Pickup-Coil to measure the magnetic flux: Standard application to measure AC currents R Torus with: y • Major radius 𝑆 = 40 𝑛𝑛 x 𝑠 0 • Minor radius 𝑏 = 5 𝑛𝑛 z • Winding with copper wire 𝑂 = 1400 𝐽 • Divided into • One segment (BCT) • Two segments (BPM in one dimension) a • Four segments Mitglied der Helmholtz-Gemeinschaft (BPM in two dimensions) R 28. September 2015 7 7

Magnetic Field of Particle Beam Model: Pencil-current with constant velocity at position ( 𝑦 0 , 𝑧 0 ) Particle Beam Pickup-Coil = 𝐽 0 ⋅ 𝑓 𝑨 Current: 𝐽 𝑦 0 𝑦 Mitglied der Helmholtz-Gemeinschaft Position: Position: 𝑧 0 𝑠 0 = 𝑧 𝑠 = 0 𝑨 Magnetic Field: 𝐶 = 𝜈 0 𝑠 −𝑠 0 × 2𝜌 𝐽 −𝑠 0 2 𝑠 28. September 2015 8

Induced Voltage 𝑉 𝑗𝑜𝑒 = − 𝑒 = − 𝑒 𝑒𝑢 𝐶 ⋅ 𝑒𝐵 𝑒𝑢 𝐶 𝜒 𝑒𝑠𝑒𝑨𝑆𝑒𝜒 2 ) leads to: 2 𝑆 Taylor of 𝐶 𝜒 to 𝒫(𝑠 0 𝑗𝑜𝑒,1/1 = 𝑒𝐽 0 𝑆 2 − 𝑏 2 𝑉 𝑒𝑢 𝑂𝜈 0 𝑆 − Beam Current Transformator † 𝑗𝑜𝑒,1/2 = 𝑒𝐽 𝑂 0 𝑆 2 − 𝑏 2 2 𝑉 2 𝜈 0 𝑆 − 1− 𝜌 𝑆 2 −𝑏 2 𝑦 0 𝑒𝑢 2 sin 2Ψ− 2𝜒 𝑏 2 Mitglied der Helmholtz-Gemeinschaft 𝑗𝑜𝑒,1/4 = 𝑒𝐽 𝑂 𝑠 0 𝑆 2 − 𝑏 2 0 2 2 𝑉 4 𝜈 0 𝑆 − 1− 𝜌 𝑆 2 −𝑏 2 𝑦 0 − 𝜌 𝑆 2 − 𝑏 2 3/2 ⋅ (𝑆 − 𝑆 2 − 𝑏 2 ) 𝑒𝑢 † “ Mutual inductances comparison in Rogowski coil with circular and rectangular cross-sections 28. September 2015 9 and its improvement ” http://dx.doi.org/10.1109/ICIEA.2008.4582770

Position Dependency Prediction of a halved Rogowski Coil Rogowski coil measures the flux density change A voltage is induced and the beam position can be determined by: 𝑦 ∝ 𝑉 𝐽𝑜𝑒,𝑚𝑓𝑔𝑢 − 𝑉 𝐽𝑜𝑒,𝑠𝑗𝑕ℎ𝑢 𝑉 𝐽𝑜𝑒,𝑚𝑓𝑔𝑢 + 𝑉 𝐽𝑜𝑒,𝑠𝑗𝑕ℎ𝑢 Theoretical prediction for position dependency of a halved coil as a horizontal BPM should be independent of the vertical beam position and the other way round Theoretical prediction signal response for a halved coil: a 𝑦 = 𝜌 𝑆 2 − 𝑏 2 Δ𝑉 1/2 Δ𝑉 1/2 2 = 𝜌 𝑆 2 − 𝑏 2 𝑦 Σ𝑉 1/2 2 Σ𝑉 1/2 Mitglied der Helmholtz-Gemeinschaft R (linear for the x direction) (R radius of the coil, a radius of the toroid) 28. September 2015 10

Technical Approach 1. Step: Development of a coil with Development of a testbench and measurements two segments (BPM in one dimension) with this coil as an horizontal BPM at COSY COSY 2. Step: Development of a coil with Installation of two Rogowski coils as horizontal four segments (BPM in horizontal and and vertical BPMs at COSY vertical direction) Mitglied der Helmholtz-Gemeinschaft 28. September 2015 11

Technical Approach 3. Step: Characterise the horizontal Rogowski BPM and the horizontal and vertical Rogowski BPM in the laboratory horizontal Rogowski horizontal & vertical BPM Rogowski BPM 4. Step: Development of a nitrogen or liquid helium cooled coil with four segments (BPM in vertical and horizontal dimension) COSY Mitglied der Helmholtz-Gemeinschaft 5. Step: Development of a SQUID-BPM test bench 28 September 2015 12

Rogowski BPM for RF Wien Filter Installation between quadrupoles • No COSY BPM next to it • Installation of Rogowski Coil BPMs at both ends • Position beam in center and parallel to Wien Filter E- and B- Field region Mitglied der Helmholtz-Gemeinschaft 28. September 2015 13

Measurement Setup Amplifier Left (13.5 dB) Amplifier Right (13.5 dB) Data COSY RF Acquisition (Reference Signal) (PC) • Unpolarised, bunched deuteron beam (N ~10 9 ), Mitglied der Helmholtz-Gemeinschaft • Momentum 970 MeV/c, revolution frequency 750 kHz • Horizontal or vertical orbit bump after 33 seconds 28 September 2015 14

Measurement horizontal Displacement • Measurement of the induced voltages every 4.45 ms for each part of the Rogowski coil • Create different horizontal orbit bumps with two correctors • Calculate the displacement as difference of the reference orbit and the orbit bump Horizontal beam position Cycle 1 Cycle 2 Displacement 2 Displacement 1 Displacement 1 Mitglied der Helmholtz-Gemeinschaft Fill Bump 1 Fill Bump 2 Fill Bump 1 Time 1 Run 28 September 2015 15

Analyse Procedure 2. Interval Position determination: 𝑦 = 𝜌 𝑆 2 − 𝑏 2 Δ𝑉 1/2 2 Σ𝑉 1/2 Δ displacement Coil Parameters: 1. Interval R = 40mm Preliminary a = 5 mm Mitglied der Helmholtz-Gemeinschaft • Define an interval of 1000 data points (4.45s) for the reference orbit (1. Interval) and the orbit bump (2. Interval) • Calculate the Δd isplacement for each measurement 28 September 2015 16

Analyse Procedure Fit function: 𝑏 + 𝐵 ⋅ sin (2𝜌𝑔𝑢 + 𝜒) Looking for 𝑏 𝜏 𝑦,𝑊𝑝𝑚𝑢𝑏𝑕𝑓 = 𝜌 1 2 + 4𝑉 2 𝑆 2 − 𝑏 2 2 𝜏 𝑉2 ≈ 3𝜈𝑛 2 𝜏 𝑉 𝜏 𝑉 ≈ 0.1 𝜈V 4𝑉 1 𝑉 2 + 𝑉 1 2 2 1. Interval 2. Interval Mitglied der Helmholtz-Gemeinschaft Fit: 𝜏 𝑏 ≈ 0.1 𝜈𝑛 (statistical error) 28 September 2015 17

Beam oscillation or mechanical vibrations? Beam position oscillation with 6 Hz • The source of this oscillation is unknown until now • With the standard COSY BPM system it is not possible to disentangle the oscillation Mitglied der Helmholtz-Gemeinschaft 28 September 2015 18

Displacement variation from cycle to cycle Determine the variation of the displacement from cycle to cycle with constant magnet settings Beam position Displacement 1 Displacement 1 Δ𝑒 Δ𝑒 = Δ𝑄 2 − Δ𝑄 1 Fill Bump 1 Fill Bump 1 Mitglied der Helmholtz-Gemeinschaft Time Cycle 1 Cycle 2 𝜏 𝑤𝑏𝑠 = 10 𝜈𝑛 28. September 2015 19

Varying Horizontal Corrector Strength 2 2 𝜏 𝑦,𝑡𝑢𝑏𝑢 = 𝜏 𝑦,𝑡𝑢𝑏𝑢 + 𝜏 𝑤𝑏𝑠 ≈ 10 𝜈𝑛 Slope −512.0 ± 0.4 𝜈𝑛/% Preliminary Mitglied der Helmholtz-Gemeinschaft Theoretical expectation is consistent with the horizontal orbit measurmenet at the accelerator 28. September 2015 20

Measurement horizontal beam dis- placement in denpendency of a vertical orbit bump Vertical beam position Changing the vertical Displacement 1 Displacement 1 orbit position with two vertical correctors Fill Bump 1 Fill Bump 1 Time Horizontal beam position Measurement of the horizontal beam position Mitglied der Helmholtz-Gemeinschaft Fill Bump 1 Fill Bump 1 Time 28. September 2015 21

Horizontal orbit measurement with vertical corrector bump 2. Interval 1. Interval Determine the horizontal Δ𝑒𝑗𝑡𝑞𝑚𝑏𝑑𝑓𝑛𝑓𝑜𝑢 between the intervals Mitglied der Helmholtz-Gemeinschaft for the different verical orbit bumps The measured horizontal beam position should be independent of the vertical beam poisition 28. September 2015 22