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Pulsed power
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Pulsed power is the science and technology of accumulating energy over a relatively long period of time and releasing it instantly, thus increasing the instantaneous power. They can be used in some applications such as food processing, water treatment, weapons, and medical applications.
Overview
[edit]Energy is typically stored as electric potential energy within capacitors, or in the case of explosive pulsed power, as chemical energy. The stored energy is released over a very short time scale resulting in a large amount of power being delivered to a load which can be used to study high energy density physics phenomena such as inertial confinement fusion using a Z-pinch, and plasma physics or to create electromagnetic radiation.
Some electrically driven pulsed power accelerators make use of pulse-forming lines to compress the current pulse before reaching the load, as is often the case when Marx generators are used as the prime power source. Other circuit architectures such as linear transformer drivers or impedance-matched Marx generators typically do not require any pulse compression.
Maximum power records
[edit]Single pulse energies as high as 100 MJ, power as high as a "few hundred terawatts" with voltages between 10 kV and 50 MV, and currents between 1 kA and 10 MA, have been achieved at least as of 2006.[1]
Applications
[edit]Fusion energy
[edit]Pulsed power systems are used in inertial confinement fusion research, most notably at the Z Pulsed Power Facility at Sandia National Laboratories, which uses Z-pinch implosions for nuclear stockpile stewardship science. The MagLIF (magnetized liner inertial fusion) program on Z has achieved the second-highest fusion triple product recorded.[2][3]
Several private companies are also developing pulsed power systems for commercial fusion power, including Pacific Fusion,[4] Fuse,[5] and First Light Fusion.[6]
Other
[edit]Railguns utilise pulsed power to quickly accelerate an object.
See also
[edit]- Crossatron – Type of gas-filled tube used as a pulsed modulator device
- Dipole magnet – Simplest type of magnet "kicker"
- Electromagnetic forming – Metal forming process
- Electromagnetic pulse – Burst of electromagnetic energy (EMP)
- Explosively pumped flux compression generator – Non-nuclear device that creates an electromagnetic pulse
- Ignitron – Gas-filled tube used as a rectifier
- Linear transformer driver
- Magnetic pulse welding
- Particle accelerator – Research apparatus for particle physics
- Power (physics) – Amount of energy transferred or converted per unit time
- Pulse-forming network – Type of electric circuit
- Thyratron – Gas-filled tube, electrical switch, rectifier
- Triggered spark gap – Two conducting electrodes separated in order to allow an electric spark to pass between
- National Ignition Facility – American nuclear fusion facility; Pulsed laser facility
References
[edit]- ^ "Pulsed Power Systems" Bluhm, Hansjoachim, 2006
- ^ Knapp, P. F.; Glinsky, M. E.; Schaeuble, M. A.; Jennings, C. A.; Evans, M.; Gunning, J.; Awe, T. J.; Chandler, G. A.; Geissel, M.; Gomez, M. R.; Hahn, K. D.; Hansen, S. B.; Harding, E. C.; Harvey-Thompson, A. J.; Humane, S. (2022-05-01). "Estimation of stagnation performance metrics in magnetized liner inertial fusion experiments using Bayesian data assimilation". Physics of Plasmas. 29 (5). doi:10.1063/5.0087115. ISSN 1070-664X. Archived from the original on 2026-02-17.
- ^ Lee, Sing; Damideh, Vahid; Btaiche, J. C. (2023-10-01). "MagLIF: Dynamics and energetics of liner and fuel". Vacuum. 216 112471. doi:10.1016/j.vacuum.2023.112471. ISSN 0042-207X.
- ^ "Pacific Fusion pulsed-power facility to host external users". www.ans.org. Retrieved 2026-05-30.
- ^ First Principles (2024-08-07). How To Build a 1-Terawatt, 600,000 Amp Pulsed Power Generator | JC Btaiche, Fuse Energy. Retrieved 2026-05-30 – via YouTube.
- ^ "First Light Fusion | News & Media | Machine 3: First Light Fusion to build pulsed power machine in search for clean, abundant energy". First Light Fusion. Retrieved 2026-05-30.
Further reading
[edit]- Gennady A. Mesyats (2005). Pulsed Power. Kluwer Academic/Plenum Publishers. ISBN 0306486539. OCLC 55616619.
Pulsed power
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Fundamentals
Definition and Principles
Pulsed power is the science and technology of storing electrical or chemical energy over extended periods, typically ranging from milliseconds to hours, and then releasing it in extremely short pulses lasting nanoseconds to microseconds, thereby achieving peak powers that far exceed those available from continuous electrical sources.[4][5] This approach enables the concentration of energy for demanding applications by compressing it both temporally and spatially, converting low-power inputs from standard transmission systems—such as 50/60 Hz alternating current or direct current—into high-intensity bursts.[4] The core principle of pulsed power revolves around energy compression to amplify output power, governed by the relationship $ P = \frac{E}{t} $, where $ P $ is power, $ E $ is the stored energy, and $ t $ is the pulse duration. By maximizing $ E $ through efficient storage and minimizing $ t $ to the nanosecond or microsecond scale, systems can attain peak powers reaching terawatts, vastly surpassing the capabilities of steady-state generators.[5] Energy is accumulated in electromagnetic fields, with electrical pulsed power relying on capacitors to store energy as $ E = \frac{1}{2} C V^2 $ (where $ C $ is capacitance and $ V $ is voltage) or inductors to store it as $ E = \frac{1}{2} L I^2 $ (where $ L $ is inductance and $ I $ is current). In contrast, explosive pulsed power harnesses the high energy density of chemical explosives to drive magnetic flux compression, amplifying currents and fields through rapid circuit deformation.[5][6] Efficient delivery of these pulses requires careful system design, particularly impedance matching between the source and load to optimize energy transfer. This involves setting the source impedance equal to the load impedance, $ Z_{\text{source}} = Z_{\text{load}} $, which minimizes reflections and maximizes power coupling, ensuring that a significant fraction of the stored energy reaches the target effectively.[7]Key Parameters and Metrics
Pulsed power systems are characterized by several core parameters that quantify their performance in delivering high-intensity electrical pulses. Peak power, often reaching terawatts (TW), represents the maximum instantaneous power output and is calculated as $ P_{\text{peak}} = V_{\text{peak}} \times I_{\text{peak}} $, where $ V_{\text{peak}} $ is the peak voltage and $ I_{\text{peak}} $ is the peak current. Typical peak powers in laboratory systems range from gigawatts (GW) to hundreds of TW, enabling extreme energy densities.[8] Pulse duration, typically on the order of nanoseconds (ns) to microseconds (μs), defines the temporal width of the output pulse and directly influences the system's ability to concentrate energy. Shorter durations, such as 100 ns in advanced facilities, allow for higher power densities but require precise control to avoid excessive heating or breakdown.[8] Energy per pulse, measured in megajoules (MJ), quantifies the total electrical energy delivered and is given by $ E = \int P(t) , dt $ integrated over the pulse width; stored energies can reach 20-30 MJ, with delivered energies often 1-3 MJ depending on system design. Rise time, the duration from 10% to 90% of peak value, is typically comparable to pulse duration (e.g., ~100 ns) and affects the sharpness of the pulse onset.[8] Repetition rate, expressed in hertz (Hz), indicates how frequently pulses can be generated, ranging from single-shot (e.g., 1 shot/day in large systems) to kHz for repetitive applications, though high rates are limited by thermal management. Voltage levels span from kilovolts (kV) to megavolts (MV), with typical laboratory ranges of 10 kV to 50 MV, while currents extend from kiloamperes (kA) to megaamperes (MA), up to 30 MA in state-of-the-art setups.[8] System impedance $ Z = V / I $ must be matched to optimize power transfer, often on the order of 0.1-1 Ω, with characteristic impedance $ Z_0 = \sqrt{L/C} $ derived from inductance $ L $ and capacitance $ C $. Efficiency metrics are crucial for assessing overall system performance. Wall-plug efficiency, defined as the ratio of output pulse energy to input electrical energy from the wall, typically ranges from 10-50% in modern systems, with values around 15% reported for high-power facilities due to losses in charging, switching, and transmission. Pulse compression ratio, the factor by which input pulse duration is shortened (or power amplified), can exceed 10^4-10^5, as seen in Marx generators where charging times of seconds are compressed to μs or ns pulses.[9] A key figure of merit is power density, often expressed as power per unit volume ($ P / V $), which scales with $ I^2 / r^2 $ for cylindrical geometries and highlights system compactness. Scalability involves trade-offs between voltage, current, and impedance; higher voltages reduce current requirements for a given power but risk dielectric breakdown (limited to ~100 MV/m in insulators), while high currents can cause magnetic core saturation (typically at 2-3 T).[8] Standardization uses SI units, with typical lab system ranges summarized below for reference:| Parameter | Typical Range | Unit |
|---|---|---|
| Peak Power | GW to 100 TW | W |
| Pulse Duration | 10 ns to 1 μs | s |
| Energy per Pulse | kJ to 30 MJ | J |
| Voltage | 10 kV to 50 MV | V |
| Current | 1 kA to 30 MA | A |
| Repetition Rate | 0.001 Hz to 1 kHz | Hz |
| Impedance | 0.1 to 10 Ω | Ω |
History
Origins and Early Developments
The conceptual foundations of pulsed power trace back to 18th- and 19th-century experiments exploring electrical discharges and electromagnetic phenomena. In 1752, Benjamin Franklin conducted his kite experiment during a thunderstorm, capturing electrical charge from lightning and demonstrating that lightning is an electrical phenomenon, thereby highlighting the potential of transient high-energy pulses in nature.[10] This work laid early groundwork for understanding pulsed electrical events, though practical applications remained distant. Building on such insights, Heinrich Hertz in 1887 generated electromagnetic waves using a spark-gap transmitter, producing short electrical pulses that confirmed the wave nature of electricity and introduced rudimentary pulsed discharge techniques central to later developments.[11] In the early 20th century, advancements in high-voltage components enabled more controlled pulse generation. During the 1930s and 1940s, high-voltage capacitors and spark gaps were developed for radar systems and lightning protection studies, allowing short, high-power pulses to simulate and investigate atmospheric discharges and radio wave propagation. A pivotal invention came in 1924 when German engineer Erwin Otto Marx designed the Marx generator, a circuit that charges multiple capacitors in parallel from a low-voltage source and discharges them in series to multiply voltage, originally for testing electrical insulators under impulse conditions.[12] This staged capacitor arrangement provided a scalable method for generating megavolt-level pulses, marking a key conceptual breakthrough in energy storage and rapid release. Post-World War II, pulsed power emerged as a distinct technology in the late 1940s and 1950s, driven by U.S. and UK nuclear weapons programs. Efforts focused on simulating nuclear explosion effects, including flash X-ray radiography for diagnosing implosion dynamics in atomic bombs, with early systems like the 1958 Febetron producing megavolt pulses to generate diagnostic X-rays.[5] Similarly, pulsed power was applied to replicate electromagnetic pulses (EMP) from high-altitude nuclear tests, which had disrupted electronics during 1950s atmospheric detonations, aiding in vulnerability assessments.[13] The Marx generator found its first significant use in this era for particle acceleration experiments, enabling high-energy beams to probe nuclear reactions.[5] Initial implementations faced substantial technical hurdles, particularly insulation breakdown under extreme voltages and the limited reliability of switches in the vacuum tube era, where plasma formation and space charge effects hindered repetitive high-power operation.[14] These challenges necessitated innovations in dielectric materials and switching mechanisms to achieve stable, high-repetition pulses for defense-related diagnostics.Key Milestones and Modern Evolution
During the 1960s and 1970s, pulsed power research in the United States advanced significantly through efforts by the U.S. Air Force and Sandia National Laboratories, focused on simulating nuclear weapon effects to test system vulnerabilities.[15][5] Sandia's program, initiated in the early 1960s, developed high-power pulse generators to replicate radiation bursts from nuclear explosions, laying the groundwork for subsequent applications.[15] Concurrently, explosive flux compression generators—devices that amplify magnetic fields using controlled detonations—matured at Los Alamos National Laboratory after initial concepts in the 1950s, enabling megajoule-level energy pulses for defense-related experiments.[16] Institutionally, the IEEE Pulsed Power Science and Technology Technical Committee formed in the mid-1970s to coordinate research, with the inaugural IEEE International Pulsed Power Conference held in 1976 in Lubbock, Texas, fostering global collaboration.[17] In the 1980s and 1990s, pulsed power technologies evolved toward Z-pinch configurations for inertial confinement fusion, compressing plasma to achieve fusion conditions through intense electrical currents.[18] A pivotal achievement was the operational debut of Sandia's Z Machine in 1996, which delivered unprecedented high-power X-ray outputs exceeding 1.8 megajoules, marking the first successful demonstration of multi-terawatt radiation sources for fusion and high-energy density physics.[19][20] These machines compressed stored electrical energy into brief, intense pulses, advancing the field beyond simulation toward energy production research. The 2000s introduced linear transformer drivers (LTDs) as a modular alternative to traditional Marx generators, enabling compact, scalable systems with faster rise times under 100 nanoseconds and currents up to 1 megaampere.[7][21] This shift supported international expansion in high-energy density physics, including China's development of the Primary Test Stand facility in the mid-2000s, a 10-terawatt Z-pinch driver for plasma experiments.[22] In Europe, efforts like the UK's MAGPIE pulsed power machine advanced Z-pinch studies for HEDP, contributing to collaborative fusion research.[23] From the 2010s onward, integration of solid-state switches, including insulated-gate bipolar transistors (IGBTs) and silicon carbide (SiC) devices, revolutionized pulsed power by supporting repetition rates exceeding 1 kHz while maintaining high voltages over 10 kV.[24][25] These advancements improved efficiency and reliability for repetitive applications in fusion and materials science. In 2024, Lawrence Livermore National Laboratory demonstrated a prototype four-stage impedance-matched Marx generator, achieving efficient energy transfer with pulse shapes mimicking laser drivers, potentially reducing system size by factors of 10 for future accelerators.[26]Technologies and Components
Energy Storage and Generation
Capacitive storage represents a primary method for accumulating electrical energy in pulsed power systems, relying on high-voltage capacitors to store charge for rapid discharge. These devices typically employ oil-filled designs, such as those using paper dielectrics impregnated with mineral or castor oil, or polymer-based dielectrics like polypropylene films, to achieve reliable insulation under high electric fields.[27] The stored energy in a capacitor follows the fundamental relation
where is the energy in joules, is the capacitance in farads, and is the voltage in volts; this electrostatic storage enables energy densities up to approximately 1 J/cc in practical configurations.[28] Limitations arise from dielectric breakdown, with typical electric field strengths constrained to around 20 MV/m to prevent insulation failure during charging or discharge.[27]
Inductive storage offers an alternative by accumulating energy in magnetic fields within inductor banks, which are arrays of coils designed for high-current operation. The energy stored magnetically is given by
where is the inductance in henries and is the current in amperes; this approach can achieve higher energy densities, up to 50 J/cm³ in advanced systems.[29] Inductor banks are often paired with compulsators, which are rotating machines that convert mechanical kinetic energy—stored in flywheels—into electrical energy through all-polyimide or air-core windings, providing efficient amplification for pulsed outputs.[30]
Chemical and explosive methods, such as flux compression generators (FCGs), provide a compact means of generating megajoule-level energies by leveraging explosives to dynamically compress magnetic flux. In these devices, a conductive armature is driven inward by a shock wave from high explosives, reducing the flux-enclosing area and thereby amplifying the magnetic field according to Faraday's law, with energy gains reaching factors of 10^4 or more in helical configurations.[31] The process relies on shock-induced compression to maintain flux conservation while converting chemical energy into electromagnetic form, enabling single-shot pulses in the MJ range without relying on static electrical storage.[32]
Hybrid systems combine capacitive and inductive elements to facilitate efficient energy transfer, such as capacitor-inductor networks that enable initial charging from standard AC mains power (wall-plug sources) through resonant circuits, bridging low-power input to high-power pulse readiness. These configurations, often involving LC oscillators, allow for controlled buildup of stored energy while minimizing losses during the transition from continuous to pulsed operation.[33]
Material considerations are critical for optimizing storage efficiency and durability, particularly in dielectrics that withstand repeated high-field stresses. Polymers like Kapton (polyimide) offer high breakdown strengths up to approximately 300 kV/mm and thermal stability to 300°C, making them suitable for compact, high-temperature capacitors, while Mylar (polyethylene terephthalate) provides a dielectric constant of 3.3 with breakdown around 295 kV/mm for lower-temperature applications.[34] In inductive systems, superconductors enable low-loss magnetic storage by eliminating resistive heating, supporting sustained current flows in high-field environments.
Recent developments as of 2025 include advancements in high-energy-density dielectrics and solid-state components for improved efficiency in fusion and defense applications.[35]
Switching and Pulse Forming Systems
Switching technologies in pulsed power systems are essential for initiating the rapid discharge of stored energy, enabling the conversion of low-power inputs into high-power outputs with precise timing. Gas switches, such as spark gaps and trigatrons, are widely employed for applications requiring voltages exceeding 1 MV due to their ability to handle extreme electric fields and high energy transfer in single-shot or low-repetition scenarios.[36] Spark gaps operate by ionizing a gas medium to create a conductive plasma channel, while trigatrons enhance reliability through an auxiliary trigger electrode that initiates breakdown with reduced jitter, typically in the range of tens of nanoseconds.[37] These switches are filled with gases like sulfur hexafluoride (SF6) or air to control breakdown voltage and arc stability, making them suitable for high-voltage environments where solid alternatives may fail.[38] Solid-state switches, including thyristors and insulated-gate bipolar transistors (IGBTs), dominate in systems demanding high repetition rates above 1 kHz, offering superior longevity and precise control without the electrode erosion issues of gas switches.[39] Thyristors provide robust current commutation in megawatt-level pulses, while IGBTs enable fast switching with low conduction losses, facilitating compact designs for repetitive operation.[40] Vacuum switches, particularly triggered vacuum switches (TVS), excel in low-jitter applications, achieving breakdown delays under 100 ns and sub-nanosecond jitter through field emission or laser triggering in a high-vacuum environment.[41] These switches maintain insulation integrity across repeated cycles, supporting high charge transfer in pulsed power architectures.[42] Pulse forming networks (PFNs) shape the output waveform to deliver tailored pulses, often rectangular in form, by leveraging transmission line principles to match load impedance and minimize reflections. Transmission line-based PFNs, such as Blumlein lines constructed from coaxial cables, generate bipolar or unipolar pulses by charging multiple lines in parallel and discharging them in series, ensuring flat-top durations determined by the line length and propagation velocity. The characteristic impedance $ Z $ of these networks is given by
where $ L $ is the inductance per unit length and $ C $ is the capacitance per unit length, allowing precise tuning to the load for efficient energy transfer.[38] Blumlein configurations double the output voltage relative to a single line while providing voltage flatness over the pulse width, critical for applications requiring consistent power delivery.
Generator topologies integrate switching and forming elements to scale power levels. Marx generators employ cascaded capacitors charged in parallel and discharged in series via gas switches, achieving voltage multiplication up to 5 MV through staged erection, with each stage contributing additive potential during breakdown.[40] This topology relies on precise spark gap timing to erect the full stack, delivering high-voltage pulses with rise times in the microsecond range. Linear transformer drivers (LTD) modules, in contrast, use parallel arrangements of capacitor-switch "bricks" within a transformer cavity to add currents rather than voltages, reducing overall system size and footprint while enabling faster risetimes through inductive coupling.[40] Each brick typically consists of a capacitor, switch, and winding, allowing modular scaling for megampere outputs in compact form factors.[43]
Pulse compression techniques further refine waveform characteristics by shortening pulse durations to enhance peak power. Saturable inductors, often wound on ferrite cores, initially present high impedance to delay current rise, then saturate under applied flux to abruptly reduce inductance, compressing rise times from microseconds to nanoseconds with compression ratios exceeding 1000.[44] Ferrite cores are selected for their high saturation flux density and low remanence, enabling repetitive operation without excessive heating, while the volt-second product determines the compression factor.[38] These magnetic elements are cascaded in multi-stage compressors to achieve sub-nanosecond edges, balancing power gain against core losses.[45]
Synchronization ensures coordinated operation across multiple stages or modules, vital for uniform pulse delivery in large-scale systems. Laser-triggered mechanisms initiate switch breakdown via focused optical pulses that photoionize the gap or electrode surface, providing jitter below 1 ns for precise timing.[46] Fiber-optic systems transmit trigger signals electrically isolated over distances up to kilometers, employing light-activated semiconductors or direct illumination to synchronize distributed switches without electromagnetic interference.[47] These methods enable sub-nanosecond alignment in multi-channel setups, enhancing overall system efficiency and waveform fidelity.[48]