High-Voltage Power Supply Scheme for Electron Microscopes Based on Superconducting Energy Storage: A Revolution in Precision and Stability

In high-end scientific instruments such as electron microscopes (EM), the stability of the high-voltage power supply directly determines imaging quality and data accuracy. Traditional power systems struggle to meet nanoscale observation requirements due to limitations in response speed, energy loss, and voltage fluctuations. The superconducting magnetic energy storage (SMES)-based high-voltage DC power supply scheme, integrating superconducting materials with power electronics, provides EM with unprecedented zero-fluctuation power support, marking a breakthrough in high-precision instrument power systems. 
1. Core Advantages of SMES Technology
1. Millisecond Response and Ultrahigh Efficiency 
   Superconducting coils exhibit near-zero resistance below critical temperatures, enabling lossless current circulation with energy efficiency exceeding 95%, far surpassing lithium batteries (85%) or supercapacitors (90%). Its millisecond response instantly compensates for grid fluctuations or load changes, suppressing voltage sags below 0.1% to prevent imaging distortion. 
2. High Power Density and Longevity 
   High-temperature superconducting materials (e.g., YBCO) at liquid nitrogen temperatures (77K) achieve current densities up to 100A/mm² and energy densities of 10⁸ J/m³. For the same power output, SMES occupies one-fifth the volume of flywheel systems. With no mechanical wear, SMES coils withstand over 500,000 charge-discharge cycles, reducing maintenance costs. 
2. System Architecture
The SMES power supply for EM comprises three core modules: 
1. Superconducting Magnet Unit 
   A toroidal high-temperature superconducting coil (e.g., 12-solenoid array) optimizes parameters like inner radius (Ri), outer radius (B0), and height (H) for uniform magnetic fields, achieving energy storage of 10+ megajoules (MJ). The coil operates in a GM cryocooler-maintained liquid nitrogen environment, with thermal leakage below 0.5W using radiation shields and HTS current leads. 
2. High-Efficiency Conversion System 
   • Front-End AC/DC Converter: An improved bridgeless power factor correction (PFC) topology employs dual switches (Q1/Q2) and diodes (D3/D4) to eliminate rectifier bridge losses, boosting power factor to 0.99 and suppressing electromagnetic interference (EMI). 
   • Bidirectional DC Converter: A non-isolated Buck/Boost topology enables efficient conversion between 380V DC bus voltage and the SMES unit (168V). Interleaved parallel design reduces current ripple by 50%, ensuring ≤±0.2% voltage fluctuation under 5kW EM loads. 
3. Intelligent Control System 
   A 12-pulse current-source converter generates quasi-24-pulse waveforms via phase-shifting transformers, limiting harmonic distortion (THD) to <1%. Coupled with mechanical superconducting switches (YBCO blocks), it achieves zero-delay current switching and transitions to backup power within 5ms during grid faults. 
3. Applications and Recent Advancements
1. Addressing EM Power Challenges 
   EM electron-optical systems are highly sensitive to voltage sags. Traditional UPS relying on batteries respond in 10–20ms, with frequent cycling accelerating degradation. SMES delivers full power in 3ms, restoring stable high-voltage supply within 0.5 seconds to maintain sub-nanometer resolution. 
2. Enabling Green Research Facilities 
   SMES recovers over 90% of braking energy (e.g., from sample stage emergency stops). Combined with renewables (e.g., photovoltaic DC integration), it reduces laboratory carbon footprints. 
3. Engineering Breakthroughs 
   In 2025, the world’s largest HTS-SMES project (5MW/10MJ) launched in China, validating megawatt-scale feasibility. Its modular magnets and low-cost cryogenics reduced SMES costs to $25/kA·m, paving the way for EM power supply commercialization. 
Conclusion
The SMES power supply scheme elevates high-voltage stability to unprecedented levels. Its trifecta of lossless storage, millisecond response, and intelligent control makes it ideal for EM and other precision instruments. As HTS material costs decline and system integration matures, this approach will expand to semiconductor manufacturing and particle accelerators, redefining energy architectures for high-precision industries.