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The Power of RF Systems: The Critical Role of High-Voltage Doorknob Capacitors in NMR Probes and Power Amplifiers
The radio frequency system of a nuclear magnetic resonance instrument is a key component for exciting atomic nuclei and receiving their weak signals. Its performance directly determines the instrument's sensitivity and accuracy. Both the high-power radio frequency pulses required by the transmitting coil and the low-noise amplifier at the front end of the receiving channel require a stable, efficient high-voltage power supply. High-voltage doorknob capacitors play a key role in pulse shaping and energy transfer.
Drawing:
Parameters:
| No. | Specification | Dissipation | Withstanding voltage | Insulation resistance | Dimension(mm) | ||||
| 1 | 20kV-2000pF | ≦0.0040 | 1.5Ur● 1min | ≧1.0×105MΩ | D | H | L | D | M |
| 2 | 20kV-10000pF | 45 | 19 | 23 | 12 | 5 | |||
| 3 | 20kV-18000pF | 65 | 15 | 19 | 12 | 5 | |||
| 4 | 30kV-1000pF | 80 | 17 | 25 | 12 | 5 | |||
| 5 | 30kV-2700pF | 45 | 24 | 32 | 12 | 4 | |||
| 6 | 30kV-12000pF | 60 | 20 | 28 | 12 | 4 | |||
| 7 | 40kV-150pF | 20 | 33 | 41 | 8 | 4 | |||
| 8 | 40kV-500pF | 28 | 33 | 41 | 8 | 4 | |||
| 9 | 40kV-7500pF | 80 | 24 | 29 | 12 | 6 | |||
| 10 | 40kV-10000pF | 80 | 22 | 26 | 16 | 5 | |||
| 11 | 50kV-1000pF | 50 | 30 | 34 | 12 | 4 | |||
| 12 | 50kV-1000pF | 32 | 27 | 31 | 16 | 5 | |||
| 13 | 50kV-5600pF | 80 | 31 | 35 | 16 | 5 | |||
| 14 | 60kV-1500pF | 50 | 31 | 34 | 12 | 5 | |||
| 15 | 60kV-3000pF | 65 | 32 | 35 | 16 | 5 | |||
| 16 | 100kV-500pF | 50 | 54 | 58 | 12 | 5 | |||
| 17 | 100kV-2000pF | 51 | 32 | 35 | 16 | 5 | |||
| 18 | Insulator type 100kV-1500pF | 68 | 36 | 40 | 16 | 5 | |||
| 19 | 150kV-820pF | 65 | 95 | 100 | 12 | 5 | |||
| 20 | 200kV-600pF | 50 | 90 | 94 | 16 | 5 | |||
Solution: Ensuring Energy for High-Fidelity RF Pulses
High-voltage doorknob capacitors play a critical role in the anode modulation circuit or DC energy storage of RF power amplifiers:
Pulse Energy Sink: During RF pulse transmission, the amplifier requires a high instantaneous current. Our capacitors act as efficient instantaneous energy reservoirs, providing high peak currents to ensure a steep leading edge and a flat top of the RF pulse.
Efficient Filtering: Their low ESR/ESL characteristics ensure extremely low high-frequency impedance on the power bus, effectively suppressing interference from power stage switching noise on the RF signal and guaranteeing a pure output waveform.
Non-Magnetic Design:
Ensuring the Performance Bottom Line of Ultra-High-Field Spectrometers
In ultra-high-field NMR instruments, any slight paramagnetic or ferromagnetic impurities can severely disrupt the uniformity of the main magnetic field. Our high-voltage doorknob capacitors are optionally constructed of completely non-magnetic materials (such as specialized ceramic dielectrics, non-magnetic epoxy resins, and silver-plated terminals) to ensure they introduce no magnetic field interference, ensuring the instrument achieves its designed resolution.