[en] The development of a high temperature coupling system was accomplished to carry out thermodynamic investigations during glass melting to solidify highly radioactive fission products into glass at a temperature up to 1200⁰C. The actual problem consisted of the fact that the gas species evaporating from the melter have to pass without condensation or without change of their composition a multistage pressure reducing system to enter the analysator unit of the mass spectrometer in the high vacuum. With the systems, offered at present, this is only possible up to approximately 450⁰C. The development of a new high temperature coupling included investigations of the gas dynamics, raw materials and thermic behaviour. (orig./EF)