Thanks to its dielectric properties and reliable surface finish, a high-quality alumina ceramic from Morgan Advanced Materials is now being successfully used in
radiotherapy equipment for oncology treatment. Deranox™ 970 is a high-density, non-porous and vacuum-tight material with a 97% aluminum oxide (Al2
) content that reportedly provides excellent electrical insulation. Frequently used in high-vacuum systems, in laser and microscope applications, and as an insulator in medical and scientific equipment, it has now been specified as the sealing element for RF windows in radiotherapy equipment.
Acting as a mechanical seal at either end of the vacuum chamber through which electron beams pass in the radiotherapy process, RF windows maintain the integrity of the vacuum, allowing electrons to pass through while preventing both ingress of contaminants and vacuum leakage.
“While most solutions for RF windows contain around 97% alumina, it is the remaining 3% that makes all the difference in dielectric performance,” explained Yannick Galais, commercial manager at Morgan Advanced Ceramics. “The alumina ceramic formulation of Deranox 970 provides a high dielectric constant (9.85 and 9.84 at 2.8 GHz and 2.9 GHz, respectively) and low loss tangent (0.00109 and 0.00110 at 2.8GHz and 2.9GHz, respectively). Externally tested and verified by an independent and fully accredited testing house to an internationally recognized standard, ASTM D2520, these properties contribute to excellent stability at high frequencies.”
Using advanced simulation techniques and extensive modeling, Deranox 970 has been tested for radiotherapy applications prior to the prototype stage to ensure its suitability—followed by in-depth, real-life testing to ensure optimum performance within a tight tolerance range. Developed alongside Deranox 970 for radiotherapy equipment, Morgan has also introduced a tailored moly-manganese metallizing ink to facilitate the bonding process when the RF window is brazed to the body of the machine, creating the optimum seal and safeguarding the vacuum. As each RF window is individually designed for specific machinery, Morgan’s inks are custom formulated for each material grade. In addition to the ceramic, Morgan is able to supply the complete RF window sub-assembly ,including mounting flanges. Innovative design features allow Morgan to offer ceramic RF windows brazed inside the oxygen free copper (OFC) vacuum chamber.
“RF windows made of Deranox 970 will last the lifetime of the radiotherapy equipment–generally 20 years plus. Within the highly time-sensitive oncology treatment pathway, disruption to therapy machinery is simply not an option, and failure of an RF window will often require full replacement of the radiotherapy machine at enormous cost to the hospital trust and causing unacceptable delays for patients,” said Galais. “The purity of our Deranox 970 material, coupled with its reliable dielectric properties and Morgan’s extensive modeling and test processes, ensure a high-quality RF window solution with long-lasting performance.”
Morgan supplies a range of other components for radiotherapy and diagnosis equipment, including high-voltage capacitors and feedthroughs. In radiology, Morgan’s ceramic-to-metal cathode insulators can be used as image amplifiers in CT and PET equipment. Similarly, in MRI systems, brazed assemblies produced by Morgan are frequently used in high-voltage, high-power applications in conjunction with super conductivity coils. Morgan also produces oncology therapy couches. Providing optimized structural design using precise fiber orientation in lay-up, the couch uses advanced composites rather than metal components to help ensure that patients are positioned correctly for optimum treatment, enabling higher image quality and lower radiation doses.