A cryostat with a PTR cooling and a boiling fluid medium including a two stage sample holder thermalization, especially convenient for AC susceptibility measurement; wherein: a 1st PTR stage is connected to a recondenser with a thermal link only; the recondenser partially penetrates through the walls of a chamber into a dewar region above a boiling fluid level, wherein the recondenser includes an integrally built thermalization point with the internal thread; whereby a 2nd PTR stage thermally connected to the thermalization block by the use of a non-flexible thermal link, wherein said thermal block includes an another thermalization point. The thermalization block enables relative vertical movement of a sample holder with respect to the cryostat without loss of excellent thermal contact with the thermalization point. Outside the vacuum chamber there are magnetic coils immersed in the boiling fluid, thus achieving substantial reduction of the parasitic effects in measurements.