Prototype Module of a Robust 18-channel Magnetometer System J. Storm, M. Burghoff, D. Drung, R. Körber IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016. Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
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Prototype Module of a Robust 18-channel Magnetometer System · 2016. 7. 31. · §History of biomagnetism at PTB Berlin: §1980 Berlin magnetically shielded room (BMSR) §1991: 37-SQUID
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Prototype Module of a Robust 18-channel Magnetometer System J. Storm, M. Burghoff, D. Drung, R. Körber
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
§ Introduction§ The prototype module§ Module and system design
§ The magnetometer
§ Field distortion due to Niobium shields
§ Noise performance of the prototype
§ Proof experiments§ Magnetoencephalography
§ ULF nuclear magnetic resonance
§ Summary
Introduction
06.07.2015 2
Outline:
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
§ History of biomagnetism at PTB Berlin:§ 1980 Berlin magnetically shielded room (BMSR)
§ 1991: 37-SQUID Multichannel System
§ 1994: 83-SQUID Multichannel System
§ 2000 Berlin magnetically shielded room (BMSR-2)
§ 2003: 304-SQUID Vector magnetometer system
Introduction
3
§ Main applications for the “old” 304 SQUIDvectormagnetometer:§ Magnetoencephalography
§ Material properties characterisation
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
This presentation gives an overview on the development of a new SQUID magnetometer system intended for high-precision in biomagnetic measurements and nuclear spin precession experiments. The following slides are a collection of several internal and external talks.
Motivation
4
§ New applications for the “new”126 SQUID vector magnetometer:§ Ultra-low-field Nuclear Magnetic Resonance
§ Quantitative imaging of magnetic nanoparticles viamagnetorelaxometry
§ Ultra-sensitive spin precession measurements fordetermination of fundamental constants of naturesuch as the electric dipole moments of 129Xenucleus
304
126 Key features of the new system: § A scalable and modular system design
§ Vector magnetometer with different field sensitivities
§ Robust against pulsed magnetic fields up to 50 mT
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
To extend the measurement capabilities at PTB Berlin, the 304-channel system will be replaced by a new SQUID vector magnetometer with up to 126 channels.
§ Introduction§ The prototype module§ Module and system design
§ The magnetometer
§ Field distortion due to Niobium shields
§ Noise performance of the prototype
§ Proof experiments§ Magnetoencephalography
§ ULF nuclear magnetic resonance
§ Summary
The Prototype Module
06.07.2015 5
Outline:
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Module and System Design – Overview
§ Top plane:1 x-y-z triplet d=17.1 mm1 hexagon d=74.5 mm
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
Overview of the multichannel module and the magnetometer arrangement. On the right hand, the intended 7-module arrangement containing 126 magnetometer channels.
• Support structure: fiber reinforced plastic (G10)
SQUID chip
niobium foil for super- conducting wire bonds
detachable contact for the pick-up coil
niobium shield d=5mm
SQUID bias pins
35 m
m
z1
z2 z3
z4
z5 z6
z7
Module and System Design – Details
7
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
Detail view on the realization of SQUID package and the different pick-up coils.
The Magnetometer control line current limiter
outp
ut v
olta
ge/
SQU
ID b
ias feedback line
16x unshunted SQ
UID
‘s
SQUID chip PTB C70-M1 PTB C7-L1
Input inductance 150 nH 400 nH
Input coupling 2.5 nH 4.1 nH
Current limiter Ioff=20 µA, Ion=1 µA
Flux antenna r=8.5×10-3 m raq=37.3×10-3 m
Loop area 2.3×10-4 m² 4.4 ×10-3 m²
loop inductance 58.4 nH 325.5 nH
tp inductance »20-50 nH
Field sensitivity 822-930 pT/F0 86-90 pT/F0
SQU
ID c
hip
flux
ante
nna
rloop
twisted pair
small magnetometer
large magnetometer
8
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
Schematic illustration of the magnetometer and the base parameters of the SQUID-current sensors used for the 17.1 mm and the 74.5 mm diameter pick-up coils respectively.
Field Distortion Due to Niobium Shields
0 -50 -100 -150 -200 -250 -300-2,0x10-3
-1,5x10-3
-1,0x10-3
-5,0x10-4
0,0
measured data @ B0= 65µT FEM solution
Bz(r=
0,z)
-B0 /
B0
z (mm)
0 10 20 30 40 50-50
-40
-30
-20
-10
0
z (m
m)
-0.10-0.08-0.06-0.04-0.020.000.020.040.060.080.10
B0
DBz/B0
r (mm)
single shield multichannel arrangement xy-plane yz-plane
B0 ey
9
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
To investigate the influence of the superconducting shields to a surrounding magnetic field, FEM simulations were carried out. On the left side a detailed illustration of the field distribution for a single shield and a comparison with measured values is given. Simulation data for an arrangement of 126 shields is shown on the right side.
→ The distortion of one module is one order of magnitude smaller
z = -175 mm
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
For exemplification of the results, cut lines from the simulated field data were plotted together with the normalised field profile of a 1 m in diameter Helmholtz coil.
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
Presented is the measured field noise for the z-channels of the prototype module. In the bottom plot, software gradiometers were implemented with the upper 74.5 mm magnetometer as reference. Due to the early state of development, strong electromagnetic disturbances that arise from the readout setup are visible.
§ Introduction§ The prototype module§ Module and system design
§ The magnetometer
§ Field distortion due to Niobium shields
§ Noise performance of the prototype
§ Proof experiments§ Magnetoencephalography
§ ULF nuclear magnetic resonance
§ Summary
Proof Experiments
06.07.2015 12
Outline:
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Magnetoencephalography
m e d i a n n e r v e
s e n s o r y c o r t e x
s t i m u l a t o r
13
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
In order to demonstrate the suitability of the new system, two proof experiments were carried out. At first, magnetoencephalography with somatosensory evoked brain activity. The experimental setup is shown schematically.
Magnetoencephalography
N20
s-band 450-750 Hz
k-band 850-1200 Hz
§ Ultra-low-noise EEG/MEG systems enable bimodal non-invasive detection of spike-likehuman somatosensory evoked responses at 1 kHz (T. Fedele et al. Physiol. Meas. 2015)
12 000 averages
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IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
As a comparison, here are recent results of ultra-low-noise EEG and MEG measurements. The MEG data was measured using a single channel system which has a white noise level of 0.5 fT/rtHz and a warm-cold distance of 8.8 cm at room temperature. With permission form Physiological Measurement: doi:10.1088/0967-3334/36/2/357
Magnetoencephalography
• electric stimulation at median nerve at t=0 s• N20 visible at t»20 ms after stimulation• 16200 averages
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
MEG results for N20 measurement with the prototype module
Magnetoencephalography
• electric stimulation at median nerve at t=0 s• N20 visible at t»20 ms after stimulation• 16200 averages
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
Frequency domain filtered N20 signal (sigma-range 450-750Hz).
Magnetoencephalography
• electric stimulation at median nerve at t=0 s• N20 visible at t»20 ms after stimulation• 16200 averages
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
Frequency domain filtered N20 signal (kappa-range 850-1200Hz).
Bpol To boost magnetisation of sample use prepolarisation, usually mT-range.
Bdet Expose sample to detection field, ususally µT-range.
SQUID-Sensor
Basics ULF nuclear magnetic resonance
x
z
y
t
Mz
During polarisation magnetisation Mz grows with T1.
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IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
Second proof experiment: ultra low field nuclear magnetic resonace (ULF-NMR). A step-by step description of the experimental setup is given on the next two slides. In the first step, the sample (distilled water) is polarized by a strong magnetic field.
Bdet Expose sample to detection field, ususally µT-range.
SQUID-Sensor
Basics ULF nuclear magnetic resonance
x
z
y
t
Bz at SQUID
During detection magnetisation M precesses around Bdetwith Larmor frequency w=gB and decays with T2
*.
T2* describes
dephasing of the M (spins). intrinsic + instrumental contributions.
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IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
In the second step, the polarisation field has been quickly turned off and the free precession decay of the sample is being measured in the detection field. The decay time T2* depends on intrinsic effects in the sample and on the homogeneity of the detection field over the sample volume.
Sample: distilled water detection field: 2.56 µT Polarization field: 35 mT (centre sample) Polarization time: 5 s SQUID reset time : 50 µs
Raw B-field data Filtered FID
0 1 2 3 4 5
-1,5x103
-1,0x103
-5,0x102
0,0
5,0x102
1,0x103
1,5x103
mag
. flu
x de
nsity
(fT)
t (s)
20
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
Specifications and measured time domain data of the ULF-NMR experiment.
Nuclear magnetic resonance of protons
Experimental setup: Sample inside polarising coil
Detection field coil
Sample: distilled water detection field: 2.56 µT Polarization field: 35 mT (centre sample) Polarization time: 5 s SQUID reset time : 50 µs
Amplitude spectra with the respective fits
Points are data Fit: Lorentzian to data real and imaginary parts ® Resonance frequency: 108.97 Hz ® T2* (for bottom z-magnetometer): 1.75 s
Parameters are in accordance with expected values
107,0 107,5 108,0 108,5 109,0 109,5 110,0 110,50
20
40
60
80
100
120
x1 x2 x3 xo y1 y2 y3 yo z1 z2 z3 z4 z5 z6 z7 Zu zo Zo
ÖSB (
fT/Ö
Hz)
f (Hz)
21
x3 x5 x9
y3 y5 y9
s7 z9 s9
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).
Presenter
Presentation Notes
Presented is frequency domain data of the ULF-NMR experiment. The results are in reasonable accordance with previous work and confirm the suitability of the new system for measurement methods involving pulsed magnetic fields. (Nuclear magnetic relaxation in water revisited Hartwig at al, The Journal of Chemical Physics, 135, 054201 (2011), DOI:http://dx.doi.org/10.1063/1.3623024)
Summary • 18-channel SQUID magnetometer module wasdesigned and constructed
• Different coil sizes allow maximum SNRs for differentsource depths and configurations
• The designed module forms the basis for a scalablemulti-module system (we plan a 126 channels configuration)
• Magnetic simulations of the magnetic distortions ofthe niobium shields were estimated and geometry ofthe shields optimised
• Sensitive MEG and pulsed ULF NMR experiments were performed
• Ultra-low noise performance enabled multi-channel detection of high- frequency components at around 1 kHz of somatosensory evoked activity
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® Accepted paper: A modular, extendible and field-tolerant multichannel vector magnetometer based on current sensor SQUIDs, 2016 Supercond. Sci. Technol.
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), July 2016.Paper based on this presentation: J.-H. Storm et al., Supercond. Sci. Technol. 29, 094001(2016).