Stuart InglebyStrathclyde University
Glasgow
Magnetometry Optimisation in Unshielded Environments
IntroductionStrathclydeUniversityQuantumSensors&MetrologyLab-Clocks,MagnetometryandRota?onsensorsMarch2015
25/05/16 Stuart Ingleby DAMOP 2016 2
Introduction• Unshielded
Magnetometry• Surveying• Seismology
• Performance criteria• Sensitivity• Bandwidth• Portable & scalable• Arbitrary fields• Noise rejection
25/05/16 Stuart Ingleby DAMOP 2016 3
Introduction• Unshielded
Magnetometry• Surveying• Seismology
• Performance criteria• Sensitivity• Bandwidth• Portable & scalable• Arbitrary fields• Noise rejection
25/05/16 Stuart Ingleby DAMOP 2016 4
• Single-laser NMOR• Software control & feedback• Iterative optimisation
ADC16-bit
CurrentBuffers
Lock-in
Amp
FrequencyGenera=on
UserInterfaceFiAng
Introduction• Unshielded
Magnetometry• Surveying• Seismology
• Performance criteria• Sensitivity• Bandwidth• Portable & scalable• Arbitrary fields• Noise rejection
25/05/16 Stuart Ingleby DAMOP 2016 5
• Single-laser NMOR• Software control & feedback• Iterative optimisation
ADC16-bit
CurrentBuffers
Lock-in
Amp
FrequencyGenera=on
UserInterfaceFiAng
Cs cell• 28 mm diameter• 2x10-6 torr Cs vapour• Paraffin anti-relaxation• 7 Hz intrinsic relaxation• Made in Fribourg [1]
[1] Castagna, Bison, Di Domenico, Hofer, Knowles, Macchione, Saudan, Weis, Appl. Phys. B 96, 763
NMOR resonance
• B0 // polarisation• First-harmonic
response• BRF modulation• Software
• Demodulation• Phase
correction• Regression
25/05/16 Stuart Ingleby DAMOP 2016 6
[2] T. Zigdon, A. D. Wilson-Gordon, S. Guttikonda, E. J. Bahr, O. Neitzke, S. M. Rochester, D. Budker, Opt. Express 18, 25494
B0 Orientation & Gradient
• B0 orientation• B0 // polarisation
• Relaxation [3]
25/05/16 Stuart Ingleby DAMOP 2016 7[3]S.Pustelny,D.F.JacksonKimball,S.M.Rochester,V.V.Yashchuk,D.Budker,Phys.Rev.A74,063406
B0 optimisation• Finite-field
optimisation1 Minimise Bx
By2 Set Bz3 Minimise
HWHM wrt ∇Bx ∇By ∇Bz
• Convergence 2-3 iterations• ΔB0 < 20 nT• ∇Β < 2 nT/mm
25/05/16 Stuart Ingleby DAMOP 2016 8
B0 optimisation• Finite-field
optimisation1 Minimise Bx
By2 Set Bz3 Minimise
HWHM wrt ∇Bx ∇By ∇Bz
• Convergence 2-3 iterations• ΔB0 < 20 nT• ∇Β < 2 nT/mm
25/05/16 Stuart Ingleby DAMOP 2016 9
B0 optimisation• Finite-field
optimisation1 Minimise Bx
By2 Set Bz3 Minimise
HWHM wrt ∇Bx ∇By ∇Bz
• Convergence 2-3 iterations• ΔB0 < 20 nT• ∇Β < 2 nT/mm
25/05/16 Stuart Ingleby DAMOP 2016 10
B0 optimisation• Finite-field
optimisation1 Minimise Bx
By2 Set Bz3 Minimise
HWHM wrt ∇Bx ∇By ∇Bz
• Convergence 2-3 iterations• ΔB0 < 20 nT• ∇Β < 2 nT/mm
25/05/16 Stuart Ingleby DAMOP 2016 11
B0 optimisation• Finite-field
optimisation1 Minimise Bx
By2 Set Bz3 Minimise
HWHM wrt ∇Bx ∇By ∇Bz
• Convergence 2-3 iterations• ΔB0 < 20 nT• ∇Β < 2 nT/mm
25/05/16 Stuart Ingleby DAMOP 2016 12
B0 optimisation• Finite-field
optimisation1 Minimise Bx
By2 Set Bz3 Minimise
HWHM wrt ∇Bx ∇By ∇Bz
• Convergence 2-3 iterations• ΔB0 < 20 nT• ∇Β < 2 nT/mm
25/05/16 Stuart Ingleby DAMOP 2016 13
B0 optimisation• Finite-field
optimisation1 Minimise Bx
By2 Set Bz3 Minimise
HWHM wrt ∇Bx ∇By ∇Bz
• Convergence 2-3 iterations• ΔB0 < 20 nT• ∇Β < 10 nT/mm
25/05/16 Stuart Ingleby DAMOP 2016 14
BRF optimisation• Signal
• Saturation
25/05/16 Stuart Ingleby DAMOP 2016 15
Optimised resonance
• HWHM 680 → 108 Hz (7 Hz intrinsic) • Sensitivity 228 → 20 pT.Hz-1/2
25/05/16 Stuart Ingleby DAMOP 2016 16
Stability & Dynamic range
25/05/16 Stuart Ingleby DAMOP 2016 17
5 μT
50 μT
• Dipole ~ 8 mA.m2
• Location < 5 mm
Response & Noise measurement• Software PID
feedback• Self-optimised
• Phase• Gain
• 1 Hz field tracking
25/05/16 Stuart Ingleby DAMOP 2016 18
Summary• QT Hub: application of QT to devices• Unshielded vapour cell magnetometry• Scalable, flexible ☞ Hardware < Software• Arbitrary fields ☞ Studying B0 & ∇B• Sensitivity ☞ Noise rejection
25/05/16 Stuart Ingleby DAMOP 2016 19
Strathclyde QT Sensors & Metrology HubAidan Arnold, Paul Griffin, Erling RiisYogeshwar Kale, Stuart InglebyVictoria Henderson, Rachel Elvin, James McGilligan