Table 1.
Measured (RDC, R1kHz, L) and as-designed (all others) physical parameters of the head-only gradient coils. RDC : DC resistance, R1kHz: resistance at 1 kHz, L: self-inductance, F, τ: maximum force and torque, respectively, η: gradient efficiency, SR/V ≡ η/L: slew rate at zero current at unit voltage, G660A: gradient at 660 A, SR1650V: slew rate at zero current at 1650 V. Gmax and SRmax are the specified maximum gradient amplitude and slew rate, respectively, taking into account any safety margins. These values were actually used in the PNS tests (except for the HG1 Z coil), and constitute “hardware limit” in the data plots (Figs. 3–5)
| para- meter |
unit | HG1 | HG2 | ||||
|---|---|---|---|---|---|---|---|
| X | Y | Z | X | Y | Z | ||
| RDC | Ω | 0.091 | 0.085 | 0.126 | 0.124 | 0.114 | 0.087 |
| R1kHz | Ω | 0.251 | 0.234 | 0.239 | 0.178 | 0.165 | 0.133 |
| L | mH | 0.341 | 0.327 | 0.266 | 0.234 | 0.204 | 0.186 |
| F | N | 2 | 10 | 5 | 8 | 10 | 118 |
| τ | Nm | 3 | 2 | 0 | 23 | 48 | 0 |
| η | mT/m/A | 0.133 | 0.133 | 0.133 | 0.129 | 0.129 | 0.132 |
| SR/V | T/m/s/V | 0.391 | 0.408 | 0.501 | 0.550 | 0.631 | 0.709 |
| G660A | mT/m | 88 | 88 | 88 | 85 | 85 | 87 |
| SR1650V | T/m/s | 645 | 673 | 827 | 908 | 1042 | 1169 |
| Gmax | mT/m | 80 | 85 | ||||
| SRmax | T/m/s | 500 | 708 | ||||