Ultrafast quenching of metals to liquid-helium temperatures - investigation of the low-temperature mobility of hydrogen in niobium

A novel technique for ultrafast quenching from 300 K to 4.2 K has been developed. It employs a fast jet of liquid helium with a speed of about 102 m/s and allows us to quench metal samples in about 6 ms. This corresponds to a quenching rate of about 4.5x104 K/s, which exceeds that achievable by conventional quenching in liquid helium by more than one order of magnitude. The technique has been used for a resistometric study of the behaviour of hydrogen in niobium quenched-in from the α-phase by means of isochronal and isothermal annealing. Even in the low-temperature region below 20 K a considerable recovery of the resistivity has been found, which cannot be seen in conventional quenching experiments. (orig.)