Glycol Substitute for High Power RF Waterloads

In waterloads for high power rf applications, rf power is dissipated directly into the coolant. Waterloads in frequency range < 1 GHz are ordinarily designed for using an ethylene-glycol water mixture as coolant. Normally a mixture of about 30% glycol and 70% deionised water is used to increase the rf absorption in the VHF-UHF range. Due to the increased ecological awareness, the use of glycol is nowadays considered to be problematic. Therefore a glycol-substitute was searched for and found. The found sodium-molybdate based substitute is actually an additive for corrosion protection in water systems. Sodium-molybdate is ecologically harmless; for instance, it is also used as fertilizer in agriculture. A homoeopathic dose of < 0.1% mixed into deionised water gives better rf characteristics than 30% glycol. The rf coolant features of this substitute were investigated and tested at our test facility for one year. In summer shut down 2004 the glycol coolant of all 14 rf systems at DORIS-3, PETRA-2 and HERAe was substituted. The results of the investigations and tests are presented.