Head: Vladimír Pavlík|
Staff: Tomáš Feher
First helium liquifier in the Košice´s low-temperature laboratory, which is commonly run by the Institute of Experimental Physics (Slovak Academy of Sciences) and the Faculty of Sciences (P.J.Šafárik University), was put into operation in 1969. It was a ZH4 liquifier manufactured by the Czechoslovak (now Czech) company Ferox Dečín. The nominal liquefaction rate of this liquifier was 4 litres of liquid helium per hour. However, with increasing demand for liquid helium from low-temperature physicists and with deteriorating liquefaction rate the question of replacing this liquifier with a modern one became more and more pressing towards the end of the seventies. After careful selection process it was decided by the investor (Slovak Academy of Sciences) to buy a model 1400 liquifier manufactured by the CTi-Cryogenics (now part of the Process Systems international, Inc.) USA.
One of the most important criterion for selecting this particular type of liquifier was its modular conception enabling to expand its production rate by simply adding additional compressor units. Another advantage of this liquifier is its ability to operate both with and without liquid nitrogen precooling. The version bought included one compressor only and its LHe production rate was 10 litres per hour with LN2 precooling. The replacement was further facilitated by the fact that some parts of the old liquefaction system could be integrated into the new system. These parts were: gasholder with oil sealing, high-pressure storage cylinders, low-pressure helium gas purifier, high-pressure recovery compressor Corblin and a large part of interconnecting piping and valves.
Reconstruction took only 3 months and the model 1400 helium liquifier was first put into operation on January 14, 1979, and within next few days the level of liquid helium began to slowly rise in the 250 l storage dewar vessel.
The liquifier operated with one compressor until 1987 when its liquefaction rate no more matches rapidly increasing demand for liquid helium (especially after the apparatus for adiabatic nuclear demagnetization was put into operation and needed to be cooled with liquid helium continuously over prolonged periods of time, typically few weeks). So the decision was made to buy a second compressor, increasing the nominal liquefaction rate to 22 l LHe per hour. An additional recovery compressor of the 4HL1K type was also added to cope with ever increasing boil-off rate from all the cryostats and dewar vessels. A battery of large high-pressure cylinders was installed outside the laboratory to increase the overall storage capacity for helium gas. The most recent alteration consisted in replacing the original 250 l helium liquefaction dewar with a 1000 l one.
On July 15th, 2006 ceremonial opening of the new helium luquifier has been held.
Starting from 1993 the liquid nitrogen needed for helium liquefier and physical experiments has been sponsored by U.S. Steel -DZ Energetika, Košice.