The concentration dependence study of the formation rate of the muon molecu
les dt mu in equilibrium double D/T and triple H/D/T liquid mixtures of hyd
rogen isotopes requires an installation consisting of a target of volume 30
cm(3) with helium cooling and a thermostabilization system. The temperatur
e of the target, close to 22 K is fixed with an accuracy of 0.1 K.