Diamond heat sink： play a critical role at the forefront of nuclear fusion research

The interior of a nuclear fusion device is one of the most extreme environments ever created by humanity. Take the International Thermonuclear Experimental Reactor (ITER) as an example: the temperature at the core of its plasma reaches an astounding 150 million degrees Celsius, ten times higher than the temperature at the Sun’s core. In addition, high-flux neutron irradiation (14.1 MeV) continuously bombards materials like microscopic projectiles, causing swelling, embrittlement, and activation. Meanwhile, bombardment by particles such as hydrogen and helium leads to surface damage including blistering and delamination. Traditional metallic materials are nearing their limits in withstanding such harsh conditions.

Diamond integrates a multitude of exceptional properties suited for extreme environments:First, it boasts an ultra-high thermal conductivity of 2000–2200 W/(m·K) at room temperature—five times that of copper—enabling it to dissipate massive local heat loads in an instant and prevent meltdown. Its thermal conductivity decreases only slightly from room temperature up to 500°C, far outperforming other materials. At the same time, diamond exhibits excellent high-temperature resistance (stable above 1400°C in an inert atmosphere), an extremely low coefficient of thermal expansion, and minimal thermal stress.

Second, diamond possesses outstanding mechanical strength and radiation resistance. As the hardest known material, it delivers unparalleled wear resistance. More crucially, its strong covalent bond structure responds uniquely to neutron irradiation: while high-dose irradiation does induce defects, partial damage can undergo "annealing" and self-repair at temperatures above 500°C. Studies have shown that after exposure to specific doses of neutron irradiation, certain diamond samples can even maintain better erosion resistance than tungsten.

Third, diamond features superior optical and electrical characteristics. With an ultra-broad transparent wavelength range spanning from 225 nm (ultraviolet) to far infrared, it serves as an ideal material for laser windows, microwave windows, and spectroscopic windows in plasma diagnostics. Its excellent insulation and high-speed charge carrier mobility also make it one of the top choices for fusion neutron detectors, such as diamond neutron probes.

Fourth and finally, diamond has low activation and low fuel retention properties. The radioactive isotopes generated in diamond (composed purely of carbon) under fusion neutron irradiation have relatively short half-lives, meeting the "low activation" requirements of fusion reactors and facilitating waste disposal and remote maintenance. Its retention of deuterium-tritium fuel is also far lower than that of metallic materials, which is favorable for fuel cycling.

Currently, diamond is playing a critical role in multiple cutting-edge fields of nuclear fusion research.

In the realm of high-power millimeter-wave transmission windows, this stands as the most mature and essential application to date. Fusion devices like ITER utilize megawatt-level millimeter waves (e.g., 170 GHz) for plasma heating and current drive. Traditional window materials face the risk of thermal stress cracking. Diamond windows ensure the efficient and reliable injection of heating waves into the plasma, serving as the lifeline for the continuous operation of fusion reactors.

In the field of plasma diagnostic windows and lenses, the Thomson scattering diagnostic system—used to measure the temperature distribution at the plasma core—requires ultra-high temperature-resistant, contamination-proof, and highly transparent windows for high-power lasers to enter and exit the vacuum chamber. Diamond windows are perfectly suited for this task, guaranteeing the accuracy and reliability of diagnostics. Furthermore, polished diamond may be used for the first mirrors facing the plasma in fusion reactors; its erosion resistance preserves mirror smoothness, ensuring long-term diagnostic precision.

For high-performance fusion neutron detection, diamond detectors offer fast response speeds, radiation resistance, high-temperature tolerance, and insensitivity to gamma rays. They can accurately measure fusion neutron flux, energy spectra, and spatiotemporal distribution in real time, acting as the critical "eyes" for monitoring fusion reaction rates and understanding burning plasma physics. For localized areas with extremely high heat loads (e.g., divertor target plates), diamond composites or coatings represent highly promising solutions. With its high strength, high thermal conductivity, and broad transparency from ultraviolet to infrared, diamond emerges as the unparalleled choice, withstanding extreme laser fluxes and ensuring implosion symmetry.

From a macroscopic perspective, the application of diamond in nuclear fusion exemplifies humanity’s use of extreme materials to harness extreme energy. It is not merely a solution to engineering challenges, but also has the potential to inspire new fusion reactor design concepts—such as more compact, higher power density fusion devices based on diamond windows and high-thermal-conductivity diamond armor.

CSMH uses the MPCVD method to prepare large-sized and high-quality diamonds,and currently has mature products such as diamond heat sinks, diamond wafers, diamond windows,diamond  composite materials,etc.Among them,the thermal conductivity of diamond heat sinks is 1000-2200w/（m.k）, which has been applied in aerospace, high-power semiconductor lasers, optical communication, chip heat dissipation, nuclear fusion and other fields.