in the article : "Sapphire is an excellent insulator which wels reduce leakage currents, as well as spurious currents from such things as radiation. Radiation

in the article : "Sapphire is an excellent insulator which wels reduce leakage currents, as well as spurious currents from such things as radiation. Radiation tolerance is perhaps what SoS became known for most, but its low power performance was what HP was after in the 1970’s."