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THE QUEST FOR ABSOLUTE ZERO.

LA QUETE DU ZERO ABSOLU.

Author(s) : POBELL F.

Type of article: Article

Summary

SINCE 1970, THE MINIMUM TEMPERATURE TO WHICH SAMPLES COULD BE COOLED WAS CONSIDERABLY LOWERED. BY ELECTRONIC ADIABATIC DEMAGNETIZATION, 0.085 K WAS OBTAINED IN 1934. NUCLEAR DEMAGNETIZATION, AFTER PRECOOLING TO 12 MILLIK AND USING A 3 T FIELD ENABLED KURTI, IN 1956, TO COOL COPPER CORES TO ABOUT 1 MICROK DURING A FEW MINUTES (BUT THE ELECTRONS AND NETWORK REMAINED AT 12 MILLIK). THE DIFFICULTY IS IN TRANSFERRING THE ULTRALOW TEMPERATURE TO THE WHOLE SAMPLE AND TO MAINTAIN ITA LONG ENOUGH TIME FOR MEASUREMENTS. AT THE BEGINNING OF THE 1970'S, THE HELSINKI GROUP COMBINED THE DILUTION REFRIGERATOR AND A 8 T FIELD. AT JULICH (FRG), BY ADDING A SECOND NUCLEAR MAGNETIC COOLING STAGE, A COPPER SAMPLE WAS OBTAINEDAT 41 MICROK (MAINTAINED BELOW 50 MICROK OVER 10 DAYS) ; APPLYING THE SAME PROCESS, 27 MICROK WAS REACHED IN TOKYO IN 1983. A RECENT UNIT AT BAYREUTH (FRG) PROVIDES A STILL BETTER RESULT BY PREVENTING HEAT LEAKAGES AS MUCH AS TO 3.5 MILLIK IN A 9 T FIELD, THE RECORD TEMPERATURE OF 12 MICROK WAS OBTAINED BY DEMAGNETIZATION. R. T.

Details

  • Original title: LA QUETE DU ZERO ABSOLU.
  • Record ID : 1989-0820
  • Languages: French
  • Source: Recherche - vol. 19 - n. 200
  • Publication date: 1988/06
  • Document available for consultation in the library of the IIR headquarters only.

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