#485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy

Comprehensive explanation of fusion (combining light elements) versus fission (splitting heavy elements), the physics of e=mc², and fuel sources. Fusion uses deuterium from seawater providing 100 million to 1 billion years of fuel at current electricity usage. Discussion of strong nuclear force, electromagnetic repulsion, and why fusion requires 100+ million degree temperatures.

• •Fusion combines hydrogen isotopes (deuterium) from seawater - virtually unlimited fuel for millions of years
• •Fission splits uranium/plutonium at room temperature; fusion requires overcoming electromagnetic repulsion at 100M+ degrees
• •Mass defect in both processes converts to energy via e=mc² - fusion releases energy up to iron on periodic table
• •Deuterium (heavy hydrogen) exists in all water on Earth - one isotope heavier than normal hydrogen with added neutron
• •Fusion fuel cannot be monopolized or controlled geopolitically unlike oil, gas, or uranium

Deep dive into why fusion is fundamentally safe versus fission reactors, the impossibility of fusion weapons, and regulatory classification. Fusion generators (not reactors) shut off instantly when fuel stops, contain only 1 second of fuel at any time, and are regulated like particle accelerators under NRC Part 30, not Part 50 for nuclear reactors. Discussion of Chernobyl, Fukushima, and human factors in nuclear accidents.

• •Fusion cannot create nuclear weapons - even 'hydrogen bombs' are 90% fission reactions using uranium
• •Proliferation experts actively encourage fusion deployment to prevent uranium enrichment worldwide
• •Fusion systems contain only 1 second of fuel - meteor strike wouldn't require evacuation, fuel safely disperses
• •Regulated under NRC Part 30 (like hospitals/accelerators) not Part 50 (nuclear reactors) - landmark 2024 Advance Act
• •Modern fission reactors are engineered safe, but human factors (operating beyond design life) caused major accidents
• •Helion received first fusion system license in 2020 from Washington State Department of Health as particle accelerator

Overview of major fusion approaches including inertial fusion (laser compression at NIF achieving nanosecond pulses), magnetic fusion (tokamaks and stellarators holding plasma continuously), and the fundamental physics of magnetic fields trapping charged particles. Explains how electromagnetic coils with mega-amp currents create magnetic bottles and the challenges of particle confinement.

• •Inertial fusion (NIF) uses high-power lasers to compress fuel for nanoseconds - achieved ignition milestones
• •Stellarators have perfect mathematical solutions but are extremely difficult to build - Wendelstein 7-X is premier example
• •Tokamaks bend solenoid magnets into donuts to prevent end losses - most common magnetic approach
• •Magnetic fields trap charged particles in gyro-orbits measured in inches, not nanoscale
• •All approaches need high temperature (velocity), high density, and sufficient confinement time for fusion
• •Fundamental physics is 1800s-1900s era - engineering integration into power plants is the hard part

Revolutionary explanation of how Helion's FRC approach works by rapidly reversing magnetic fields in microseconds, causing plasma to self-organize into closed-field configurations. Unlike tokamaks where external magnets confine plasma, FRCs have plasma current generating its own magnetic field - similar to solar flares. Detailed physics of field reversal, plasma reconnection, and transformer-like induction.

• •Rapid field reversal (faster than microsecond) causes plasma to reconnect and form self-confining magnetic bottle
• •Plasma itself carries massive electrical current that generates confining magnetic field - 'plasma makes the magnets'
• •Based on 1950s theta-pinch experiments that hit technological limits before semiconductors existed
• •Similar to solar flares/plasmoids observed in nature - self-organized plasma structures
• •Requires semiconductor switching to reverse 100+ megaamps in microseconds - impossible in 1950s
• •Linear topology (not donut) allows for direct electricity generation and simpler engineering

Technical deep-dive into plasma beta (ratio of particle pressure to magnetic pressure), why high-beta FRCs are inherently unstable, and how Helion achieves stability through the S*/ε parameter. Explains tilt instability using spinning top analogy - FRCs need high kinetic energy (fast spin) and elongation (geometry) to remain stable for milliseconds instead of microseconds.

• •Plasma beta ≈1 in FRCs means particle pressure equals magnetic pressure - direct relationship between B-field and density/temperature
• •High beta plasmas are unstable - whole configuration can tilt over like unstable top without mechanical support
• •S*/ε parameter combines kinetic stability (spinning fast like top) with geometric elongation (like duct tape roll vs coin)
• •Theory predicts microsecond lifetimes, but proper S*/ε design achieves thousands of microseconds - 1000x improvement
• •Must maintain stability while heating from cold to 100M degrees - requires extremely fast electrical engineering
• •Temperature IS velocity at fusion scales - 100M degrees = millions of miles per hour particle motion

Helion as fundamentally an electrical engineering company managing tens of thousands of parallel switches operating at 100+ megaamps with microsecond precision. Discussion of control systems using FPGAs, assembly language programming, fiber optic triggering, and diagnostic systems measuring plasma parameters in real-time to enable feedback control.

• •Systems use 100 million amps total - each switch handles 30,000 amps requiring tens of thousands in parallel
• •Control via gigahertz FPGAs programmed in assembly language, triggered by fiber optics (nanosecond response)
• •Diagnostics measure magnetic fields, interferometry, spectroscopy in microseconds for real-time feedback
• •Pre-programmed sequences from numerical simulations, then real-time adjustments based on sensor data
• •Modern gigahertz processors enable 1000 operations per microsecond - critical for control loops
• •Legacy Fortran code for fusion physics, Python for analysis, assembly for real-time control

Multiple heating methods to reach fusion temperatures: adiabatic compression (PdV work like diesel engine), neutral beam injection of 1+ megawatt beams, and alpha heating from fusion products. Explains Q-factor (energy out/energy in), breakeven at Q=1, and path to Q>1 through compression and beam heating working together.

• •Adiabatic compression does PdV work - compressing plasma 10x increases temperature 10x (like diesel engine)
• •Neutral beam injection: accelerate deuterium to 100+ keV, strip electrons, inject into plasma at 1+ MW power
• •Beams must be neutral to penetrate magnetic fields - ions would be deflected
• •Alpha particles from fusion deposit energy back into plasma - enables self-heating at high enough fusion rates
• •Q-factor measures energy gain - need Q>1 for net energy, targeting much higher for commercial viability
• •Compression and beam heating are complementary - compression sets up conditions, beams push over threshold

Revolutionary direct electricity generation by expanding hot plasma through reversed magnetic field - charged particles induce current directly in coils without steam turbines. Explains how pulsed operation with capacitor storage enables continuous grid power, and why this is more efficient than thermal conversion used in fission/tokamaks.

• •Expanding plasma through reversed magnetic field directly induces electrical current in coils - no turbines needed
• •Pulsed operation at ~1 Hz with capacitor banks provides continuous power to grid
• •50+ year old capacitor technology proven reliable - simpler than steam turbine systems
• •Direct conversion potentially 90%+ efficient vs ~30-40% for thermal steam cycles
• •Eliminates entire thermal management system, cooling towers, and associated complexity
• •Enables smaller, modular designs compared to gigawatt-scale thermal plants

Helion's development path from 7 prototype generations to Polaris (50 MW demonstration) and commercial deployment by 2028. Discussion of Microsoft power purchase agreement, scaling challenges, manufacturing approach, and why fusion timing is critical for AI data center power demands. Emphasis on iterative engineering approach and learning from each prototype.

• •Built 7 prototype generations, each demonstrating key physics and engineering milestones
• •Polaris: 50 MW demonstration system currently under construction, targeting net electricity production
• •2028 target for commercial fusion generator backed by Microsoft power purchase agreement
• •AI data centers creating urgent demand for clean baseload power - fusion timing aligns with need
• •Manufacturing approach focuses on modular, repeatable components rather than one-off construction
• •Each prototype 2-3 year development cycle - rapid iteration compared to traditional fusion programs
• •Scaling primarily about replicating proven modules rather than building larger single units

Discussion of advanced fusion fuels beyond deuterium-tritium, particularly deuterium-helium-3 which produces charged particles (protons) instead of neutrons, enabling even more efficient direct conversion. Explains why D-He3 requires higher temperatures but offers advantages for electricity generation and reduced activation.

• •D-He3 fusion produces charged particles (protons) directly usable for electricity - minimal neutron production
• •Requires ~3x higher temperature than D-T but Helion's compression approach can achieve this
• •Helium-3 can be bred from deuterium reactions in the fusion process itself - self-sustaining fuel cycle
• •Aneutronic reactions reduce material activation and shielding requirements significantly
• •Charged particle products enable higher direct conversion efficiency than neutron-producing reactions
• •Represents next generation beyond D-T approach used by most fusion programs including ITER