Technology-grade lab-grown diamonds (often called CVD diamonds after the Chemical Vapor Deposition process used to grow them) are becoming critical infrastructure for the nuclear fusion industry. Unlike gemstone diamonds, these are engineered for extreme thermal, optical, and radiation-resistant properties.
Companies in the fusion sector use them primarily in three ways: heating the plasma, monitoring the reaction, and managing extreme heat.
1. Microwave “Windows” for Plasma Heating
In magnetic confinement fusion (like Tokamaks), the hydrogen plasma must be heated to over 150 million°C.
This is done using high-power microwaves (from devices called gyrotrons).
The Challenge: These microwaves carry megawatts of power. Most materials would melt or shatter instantly when that much energy passes through them.
The Solution: CVD diamond is the only material that is both transparent to microwaves and has high enough thermal conductivity to dissipate the heat generated by the beam.
Usage: Companies manufacture diamond “disks” (up to 180mm in diameter) that act as a vacuum seal. They allow the microwave beam to enter the reactor while keeping the radioactive fuel (tritium) securely inside.
2. Radiation-Hardened Sensors and Detectors
The environment inside a fusion reactor is incredibly “noisy” and radioactive,filled with high-energy neutrons that destroy standard silicon-based electronics.
Neutron Monitoring: Diamond is naturally “radiation-hard.” Companies use diamond-based detectors to count the neutrons flying out of the plasma. This is the primary way scientists measure how much fusion power the reactor is actually producing (the “burn rate”).
Plasma Diagnostics: Because diamond can operate at high temperatures and high radiation without failing, it is used for ultraviolet (UV) and X-ray sensors that monitor the stability of the plasma in real-time.
3. Inertial Confinement Fusion (ICF) Fuel Capsules
In laser-driven fusion (like the experiments at Lawrence Livermore National Laboratory), the fuel is contained in a tiny, peppercorn-sized sphere.
The Ablator: High-grade diamond is used as the shell (the “ablator”) for these fuel pellets.
Why Diamond? When hit by high-power lasers, the diamond shell vaporizes in a very specific, uniform way. This creates a massive inward-facing shockwave that compresses the fuel evenly to ignite the fusion reaction. Diamond’s high density and structural uniformity are essential for achieving the perfect “implosion” needed for ignition.
4. Extreme Thermal Management
Fusion components are subject to the highest heat fluxes of any industrial application on Earth.
Heat Sinks: Diamond has a thermal conductivity of roughly 2200 W/mK, which is about 5 times higher than copper.
Component Protection: Companies use diamond-composite materials or diamond coatings to protect sensitive electronic components and magnets located near the reactor core, ensuring they don’t overheat even when the reactor is running at full power.
Summary of Diamond Properties in Fusion
| Property | Application in Fusion |
|---|---|
| Highest Thermal Conductivity | Cooling high-power electronics and gyrotron windows. |
| Wide Bandgap / Transparency | Allowing microwaves and lasers to pass through without energy loss. |
| Radiation Hardness | Long-lasting sensors that don't degrade under neutron bombardment. |
| High Density / Uniformity | Perfect compression of fuel pellets in laser fusion. |