Reactor tests of ion thermometers

An ion thermometer of UNIHOST boron-free glas with a built-in thermocouple was tested in the reactor core of the WWR-S reactor. The detector was fitted in stainless steel and filled with powder MgO. The use of boron-free glass reduced the systematic measurement error caused by the energy of the 10B(n,α) reaction. The disadvantage of this glass is its high alkali content which causes poor chemical resistance, a low electrical resistance and a low transformation temperature. It may be used for temperatures of up to 400 degC and after special treatment with sulfuric acid. The dispersion of values in the individual detectors in 1 to 2 K. (M.D.)