Nuclear fusion diamonds

Nuclear fusion diamonds

Polycrystalline CVD diamond is used for the output windows of high-power microwave tubes.

Diafilm RF
Element Six Diafilm RF polycrystalline CVD (chemical vapour deposition) diamond has been engineered to meet the needs of nuclear fusion, which is the next generation of clean, renewable energy.

Much attention has recently been focused on improving the dielectric properties of CVD diamond in the mm wave band. Measurement of these properties is typically made at 145 GHz on samples of material at least 30 mm (1.18”) in diameter and in excess of 0.85 mm (0.034”) thick, depending on frequency. Samples having a dielectric loss tangent (tan d) in the range of 100-100x10-6 can routinely be achieved in diameters up to Ø135mm and 3.0mm thick.

Low dielectric loss materials find application as the output windows of high-power microwave tubes. A specific case is that of windows for gyrotron tubes operating in the 70 to 170 GHz frequency region with output powers in excess of 2MW. A specific requirement in this application is that the window needs to be larger than 100 mm (4”) in diameter, 1.6 mm to 2.3 mm (0.063” to 0.091”) thick depending on microwave frequency, and that the loss should be relatively uniform over the area of the window to avoid hot spots. CVD diamond is the only material capable of facilitating continuous waves at powers in excess of 2MW without resorting to exotic cryo-cooling systems, as is the case with sapphire.

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