Neutron generators are compact neutron source devices that produce neutrons through charged particle acceleration and nuclear reactions. Featuring small size, light weight, high neutron yield, switchable output, no nuclear waste and high operational safety, they are widely applied in oil & gas neutron logging, online elemental analysis for industrial materials, explosive & drug detection for customs and security inspection, radiation breeding, neutron radiography, Boron Neutron Capture Therapy (BNCT) for cancer treatment, and nuclear physics experiments. The high‑voltage pulse power supply acts as the core power component of neutron generators, providing high‑amplitude, fast‑rise, narrow high‑voltage pulses for ion sources and acceleration tubes. It accelerates deuterium‑tritium ions to sufficient energy to bombard target materials, triggering D‑T nuclear reactions and releasing neutrons. The pulse amplitude, edge steepness, pulse width, repetition frequency and waveform quality directly determine neutron yield, neutron energy, pulse duration, yield stability and overall equipment performance. Neutron generators impose extremely stringent technical requirements fundamentally different from conventional pulse power supplies: 1.High‑amplitude nanosecond fast rising edge: Pulse amplitude ranges from tens of kV to hundreds of kV, and reaches several MV for industrial and scientific models. The rising edge must be controlled within tens of nanoseconds or even single nanoseconds, with symmetric falling edges, overshoot below 0.5%, and no oscillation or tailing. Traditional pulse power supplies cannot balance high voltage and nanosecond edges due to topology limitations, parasitic parameters and switching speed, resulting in insufficient ion energy, low neutron yield, energy dispersion or failed nuclear reactions. 2.Narrow pulse & high repetition frequency: Pulse width is adjustable from tens of nanoseconds to tens of microseconds; repetition frequency covers single pulse up to hundreds of kHz with pulse parameter consistency better than ±0.3%. Conventional designs suffer from severe heating, waveform distortion and amplitude attenuation at high frequency. 3.Miniaturization & high power density: Widely used in downhole logging, portable security and field monitoring. Logging power supplies must fit into narrow probes with diameter of dozens of millimeters and length within tens of centimeters, requiring power density ≥500 W/in³ and excellent structural stability. Traditional vacuum tube modulators are too bulky and heavy. 4.Extreme environmental adaptability: Downhole logging operates above 175 ℃ with strong vibration, shock, high pressure and formation radiation; portable models work from −40 ℃ to +85 ℃ under humid, dusty and high‑EMI field conditions. 5.High reliability & long service life: Long‑term operation under high voltage, high current and high‑frequency switching with risk of high‑voltage arcing. Required MTBF ≥10,000 hours with fast protection against arcing and short circuits. 6.Ultra‑low electromagnetic interference: Nanosecond fast edges generate intense radiation that disturbs high‑sensitivity neutron detection systems, requiring superior EMC performance and suppressed electromagnetic emission.
This methodology establishes a full‑process technical framework covering high‑amplitude fast‑edge topology, low‑parasitic layout optimization, nanosecond pulse waveform control, extreme environmental adaptation and high‑density integration. It supports neutron generators for logging, industrial analysis, security inspection, medical BNCT and scientific research, providing standardized design guidelines for domestic core component localization and performance upgrading. Targeting high amplitude, nanosecond fast edges, miniaturization and wide pulse tuning, the general architecture adopts an all‑solid‑state modular Marx generator + GaN wide‑bandgap power switches + distributed synchronous drive control, combined with 3D low‑parasitic layout and fully digital pulse calibration algorithms. It eliminates traditional limitations of bulky vacuum tubes, short service life and insufficient edge speed of silicon‑based devices. The Marx topology achieves high‑voltage output via parallel charging and series discharging of multi‑stage capacitors without high‑voltage transformers, avoiding edge distortion and oscillation caused by leakage inductance and distributed capacitance. All‑solid‑state GaN switches deliver faster switching, longer lifetime, higher repetition frequency and smaller size without preheating or maintenance. Six core design principles are defined.
1.Optimized wide‑bandgap power device selection: Third‑generation GaN HEMTs are adopted for all main switches, featuring ultra‑fast switching, low loss and minimal parasitic capacitance/inductance, with rise time ≤5 ns and fall time ≤10 ns. Series connection achieves high voltage with synchronous switching accuracy ≤2 ns and static/dynamic voltage sharing deviation ≤±3%. Parallel connection increases peak current with current sharing error ≤±2%.
2.Miniaturized symmetric modular Marx unit design: Identical standardized Marx units ensure consistent electrical parameters, structure and parasitic performance for fully synchronized switching and discharging. Amplitude is scaled by stage number; peak current is expanded by parallel modules with excellent interchangeability for rapid maintenance. Vertical stacked 3D integration drastically reduces size for narrow downhole installation.
3.Isolated constant‑current charging per stage: Each Marx unit integrates an independent miniature isolated DC‑DC charger with charging accuracy better than ±0.2%. Closed‑loop voltage compensation corrects drift caused by temperature, aging and frequency variation, ensuring stable inter‑pulse amplitude from single pulse to maximum repetition rate. High integration further reduces overall volume.
4.Nanosecond low‑parasitic discharge loop design: A 3D stacked busbar structure adopts ultra‑thin high‑insulation dielectric to cancel reverse current flux, limiting total loop parasitic inductance within 500 pH to minimize edge degradation, oscillation and voltage droop. Symmetric compact layout ensures identical discharge length and impedance across all stages. Coaxial output with impedance matching eliminates reflection and tailing at the acceleration tube, maintaining distortionless pulses for ion acceleration.
5.Active pulse waveform compensation & flexible tuning: FPGA‑based digital droop compensation dynamically adjusts switching timing or injects corrective current to suppress pulse top droop within 0.3%. Active clamping restricts overshoot below 0.3%; fast discharge circuits ensure symmetric falling edges and eliminate ion tail acceleration. Fully digital control enables continuous adjustment of pulse width, repetition frequency and amplitude for multi‑scenario adaptation.
6.High‑voltage insulation & integrated encapsulation: Graded electric field optimization with equalizing rings suppresses corona discharge and breakdown. High‑insulation materials such as polyimide, ceramic and high‑temperature epoxy ensure reliable isolation. Integrated full encapsulation improves thermal conductivity, vibration resistance and high‑temperature stability for extreme downhole environments.
Nanosecond synchronous drive control is critical for fast‑edge performance. A full‑link optical fiber distributed drive with local precision delay compensation achieves system synchronization ≤2 ns. Independent optical isolation drives eliminate high‑voltage coupling interference with stable transmission delay ≤10 ps/m. FPGA‑based digital delay tuning with step resolution ≤100 ps compensates individual switching delays to ensure simultaneous turn‑on/turn‑off. High‑current fast gate driving completes charging/discharging of switch capacitance within nanoseconds to further sharpen pulse edges.
Extreme environmental adaptation covers wide‑temperature operation, vibration/shock resistance, radiation tolerance and full protection against harsh field conditions: Wide‑temperature design adopts high‑temperature components (−55 ℃ ~ +200 ℃), low‑loss high‑temperature magnetic materials, high‑stable capacitors and high‑Tg encapsulation resin. Integrated thermal conduction ensures uniform heat dissipation under downhole high temperature. Mechanical reinforcement with integrated metal housing, surface‑mount components, potting fixation and reinforced soldering withstands hundreds of g shock and continuous strong vibration. Radiation‑hardened semiconductors with total dose tolerance ≥100 krad(Si) plus metal shielding ensure stable operation in formation radiation environments. Full sealing achieves IP67 protection with conformal coating and potting against humidity, dust and corrosive gas for outdoor field applications.
High reliability and EMC design ensure long‑term stable operation: Multi‑level hardware/software redundant protection provides over/under voltage, overcurrent/short‑circuit, overtemperature and arcing protection with hardware response<100 ns and automatic recovery for transient faults. Full component derating (voltage ≤50%, current ≤40%, temperature ≤70%) extends service life significantly compared with traditional vacuum thyratrons. Dual‑layer shielding (magnetic inner layer + conductive outer layer) suppresses radiation from fast edges to avoid interference with neutron detection. Multi‑stage EMI filtering and single‑point grounding eliminate conducted noise and ground loop interference.
In summary, this integrated methodology solves the core bottlenecks of conventional pulse power supplies, unifying high amplitude, nanosecond fast edges, miniaturization and high repetition frequency. Adopting all‑solid‑state Marx topology and GaN technology realizes rise edges within 5 ns and output up to hundreds of kV; low‑parasitic 3D layout delivers oscillation‑free low‑droop waveforms; extreme environmental design supports downhole operation above 175 ℃ with strong mechanical stress; integrated encapsulation achieves ultra‑high power density and compact size. Widely applicable to oil logging, industrial analysis, security inspection, BNCT medical treatment and nuclear physics research, it provides core independent controllable technology for domestic neutron generator localization and performance upgrading.