Table 2 Model fit coefficients before and after nulling for fifteen field components in the spherical harmonic model.
From: A lightweight magnetically shielded room with active shielding
Uniform field components | Field strength (nT) coils OFF | Field strength (nT) coils ON | Ratio |
|---|---|---|---|
\(B_{x} \left( {\hat{\user2{x}}} \right)\) | − 0.99 ± 0.18 | 0.14 ± 0.23 | 7.1 |
\(B_{y} \left( {\hat{\user2{y}}} \right)\) | − 4.09 ± 0.17 | − 0.44 ± 0.13 | 9.3 |
\(B_{z} \left( {\hat{\user2{z}}} \right)\) | 4.45 ± 0.15 | − 0.38 ± 0.24 | 11.7 |
Field gradient components | Field strength (nT/m) coils OFF | Field strength (nT/m) coils ON | Ratio |
|---|---|---|---|
\(y\hat{\user2{x}} + x\hat{\user2{y}}\)(\(\frac{{dB_{x} }}{dy} = \frac{{dB_{y} }}{dx}\)) | − 1.22 ± 0.24 | 0.37 ± 0.60 | 3.3 |
\(z\hat{\user2{x}} + x\hat{\user2{z}}\)(\(\frac{{dB_{x} }}{dz} = \frac{{dB_{z} }}{dx}\)) | 1.05 ± 0.31 | − 0.29 ± 0.44 | 3.6 |
\(z\hat{\user2{y}} + y\hat{\user2{z}}\)(\(\frac{{dB_{y} }}{dz} = \frac{{dB_{z} }}{dy}\)) | 2.05 ± 0.40 | 0.02 ± 0.43 | 102.5 |
\(- x\hat{\user2{x}} - y\hat{\user2{y}} + 2z\hat{\user2{z}}\)(\(- \frac{{dB_{x} }}{dx} - \frac{{dB_{y} }}{dy} = 2\frac{{dB_{z} }}{dz}\)) | − 0.12 ± 0.16 | − 0.04 ± 0.16 | 3.0 |
\(x\hat{\user2{x}} - y\hat{\user2{y}}\)(\(\frac{{dB_{x} }}{dx} = - \frac{{dB_{y} }}{dy}\)) | − 0.18 ± 0.32 | 0.13 ± 0.61 | 1.4 |
Curvature components | Field strength (nT/m2) coils OFF | Field strength (nT/m2) coils ON | Ratio |
|---|---|---|---|
\(6xy\hat{\user2{x}} + 3\left( {x^{2} - y^{2} } \right)\hat{\user2{y}}\) | 0.49 ± 0.16 | 0.08 ± 0.45 | 6.1 |
\(3\left( {x^{2} - y^{2} } \right)\hat{\user2{x}} - 6xy\hat{\user2{y}}\) | 0.09 ± 0.16 | 0.37 ± 0.26 | 0.2 |
\(yz\hat{\user2{x}} + xz\hat{\user2{y}} + xy\hat{\user2{z}}\) | 0.9 ± 1.9 | − 1.4 ± 2.4 | 0.6 |
\(2xz\hat{\user2{x}} - 2yz\hat{\user2{y}} + \left( {x^{2} - y^{2} } \right)\hat{\user2{z}}\) | − 0.47 ± 0.74 | − 0.27 ± 0.97 | 1.7 |
\(- 2xy\hat{\user2{x}} + \left( {4z^{2} - x^{2} - 3y^{2} } \right)\hat{\user2{y}} + 8yz\hat{\user2{z}}\) | − 0.15 ± 0.12 | − 0.25 ± 0.20 | 0.6 |
\(\left( {4z^{2} - 3x^{2} - y^{2} } \right)\hat{\user2{x}} - 2xy\hat{\user2{y}} + 8xz\hat{\user2{z}}\) | − 0.03 ± 0.15 | − 0.11 ± 0.20 | 0.3 |
\(- 6xz\hat{\user2{x}} - 6yz\hat{\user2{y}} + \left( {6z^{2} - 3x^{2} - 3y^{2} } \right)\hat{\user2{z}}\) | − 0.19 ± 0.16 | 0.02 ± 0.20 | 9.5 |
