MEASUREMENT OF THERMODYNAMIC TEMPERATURES USING NOISE AND NUCLEAR ORIENTATION THERMOMETERS

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MEASUREMENT OF THERMODYNAMIC

TEMPERATURES USING NOISE AND NUCLEAR ORIENTATION THERMOMETERS

H. Marshak, R. Soulen, Jr

To cite this version:

H. Marshak, R. Soulen, Jr. MEASUREMENT OF THERMODYNAMIC TEMPERATURES USING

NOISE AND NUCLEAR ORIENTATION THERMOMETERS. Journal de Physique Colloques, 1978,

39 (C6), pp.C6-1162-C6-1163. �10.1051/jphyscol:19786514�. �jpa-00217999�

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JOURNAL DE PHYSIQUE Colloque C6, supplPrnent au no 8, Tome 39, aotit 1978, page C6- 1 162

MEASUREMENT OF THERMODYNAMIC TEMPERATURES U S I N G N O I S E AND NUCLEAR O R I E N T A T I O N THERMOMETERS

H. Marshak and R.J. Soulen,Jr.

Nationai! Bureau of Standards, Washington, D.C. 20234

,

USA.

Rdsum6.- Nous avons compare les Cchelles obtenues 1 partir des thermomstres 1 orientation nucldaire avec celles obtenues 1 partir des thermomstres 1 bruit 0,011 K 2i 0,05 K et avons obtenu un accord

5 & 0,5 % prss.

Abstract.- We have compared 6 0 ~ o y-ray anisotropy and Josephson junction noise thermometers from 0.011 K to 0.05 K and have obtained agreement to within C 0.5 %.

INTRODUCTION.- At NBS we have been comparing the temperature scales obtained from both "CO y-ray anisotropy thermometers /I/ and Josephson junction noise thermometers 121 in order to define a thermo- dynamiccryogenic temperature scale. We have reported results previously /3,4/ on data obtained when the two thermometers were simultaneously compared on a dilution refrigerator from 0.011 to 0.035 K.

This article describes several changes made in both thermometers and on new data obtained which now ex- pands the comparison from 0.011 to 0.050 K.

NOISE THERMOMETERS.- The noise thermometer is of the R-SQUID design in which the noise-generating resistor is connected in parallel to a point-contact Josephson junction. An improved noise thermometer, labeled T -4, was used in these experiments. It em-

N

ployed a bias resistor which was less sensitive to temperature (dR/dT

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^{7.8 x}^10-l1Q/mK) and which was in better thermal contact with the bath. Finally, on the basis of recent results of Soulen and Giffard /5/, some systematic errors due to the presence of the Josephson junction were eliminated.

NUCLEAR ORIENTATION THERMOMETERS.- The data reported here for the 6 0 ~ o in hcp 5 9 ~ o single crystal y-ray anisotropy thermometer'were obtained using two different thermometers ; thermometer T -1 is

Y the one used in our previous work /3,4/ ; T -2 is

Y identical to T -1 except that it has about 5 times

Y

more activity (-. 10 uCi), thus making it more use- ful for high temperature measurements where the anisotropy is very small.

The temperatures were derived from the measured anisotropies as described previously /3,4/.

The only change was in the value used for the hyperfine splitting. A very accurate and direct measurement of the hyperfine splitting for 6 0 ~ o in hcp single 5 9 ~ o has recently been made by Zech, Hagn, Ernst and Eska /6/ using NMR/ON. They measured a value o<

126.79(5) MHz for the frequency parallel to the c- axis in zero external field. This corresponds to a splitting of 6.0850 2 0.0024 mK.

INTERCOMPARISON.- In our previous experiments /3,4/

the noise and nuclear orientation thermometers were compared directly, i.e. both thermometers were moun- ted on the dilution refrigerator and data were ac- cumulated simultaneously. At the same time, a ger- manium resistance thermometer (GeRT) was used in a temperature feedback circuit to stabilize the temperature of the cryostat at different values of resistance, thereby calibrating this secondary thermometer against the two primary thermometers. The data reported here for the noise and nuclear orientation thermometers were taken at identical resistance values for the above GeRT, but not necessa- rily during the same experiment. Independent infor- mation indicates that any inaccuracies introduced by use of the GeRT is less than 0.1 mK.

In figure 1 we show the data for both 6 0 ~ o y-ray anisotropy thermometers, T -1 and T -2 and

Y

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Y for the new Josephson junction noise thermometer T -4. The difference between the mean temperatures

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N

T and ?; is plotted against the average tempera- Y N- -

ture T = (T +T 112. The uncertainties of the two -t

N

thermometers, r.e. r(~y~j'+(by~)q~? The closed circles represent the old data T taken with T -I

Y Y

/4/ but recalculated using the more accurate value.

for the hyperfine splitting as explained previously.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19786514

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The open circles represent the data for T -2.

Y ned in the past, we might expect to improve the comp- parison to obtain agreement within a few tenths of a percent.

I I I I I We also plan to continue the comparison to

+I.@ - - higher temperatures. In this case TN-4 will be com-

+05-

-

pared with a y-ray thermometer using 166%o in hcp

- -

Ty-TM single crystal 6 5 ~ o . This y-ray thermometer, which

ImK)

presently under investigation, is expected to cover

-05-

the temperature range from

-

^{0.05 K to}

-

^1.0^K.

1

I I I I I ACKNOWLEDGEMENT.- It is a pleasure to acknowledge

0 10 20 30 40 50 60

( T ) = fly+ ?,~/z.(~KJ the technical assistance of Mr. R.B. Dove.

Fig. 1 : the temperature differences between the 6 0 ~ o y-ray anisotropy thermometer,Ty-, and the Jo- sephson junction noise thermometer, TN. The closed circles are for Ty-1 and the open circles for T -2 (see text).

Y

In general, the overall agreement between the

"CO y-ray anisotropy and noise thermometers as shown in figure 1 is within 1 % (see the 1 % guide- lines) and, in fact, about 2/3 of the data points lie within 0.5 %. We emphasize that "raw" data are given here ; there has been no attempt to smooth the data in any way. In addition, the intercomparison of the two thermometers has now been extended to

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0.05 K using the more active T -2 thermometer.

Y

We regard these results as quite satisfying especially above 0.035 K, where the nuclear orientation thermometer becomes increasingly insensitive.

We attribute the ability to measure such small anisotropies both to the improved temperature stabili- ty of the cryostat (temperature fluctuations less than 10 pK over periods of 24 h) and to the stabi- lity of the y-ray counting system. In fact, one additional data point was obtained at 0.064 K where the anisotropy was only 1.6 %. Even at this temperature, the agreement between the two thermometers was within the 2 % statistical uncertainty of the measurement (due mostly to the y-ray thermometer).

CONCLUSIONS.- We have demonstrated that a temperature scale from 0.011 K to 0.05 K based on the com- parisons of two primary thermometers can be defined with an inaccuracy of 0.5 %. In view of the possi- bility that the use of the GeRT as the intercomparison device may have introduced a small temperature uncertainty in the data, we intend to compare the improved thermometers simultaneously in the near future. Based on the statistical imprecision obtai-

References

/ I / Thorp,T.L., Triplett,B.B., Brewer,W.D., Phillips,

N.E., Templeton,J.E., Start,T.W. and Schmidt, P.H., J. Low Temp. Phys. 3 (1970) 589

Berglund,P .M., ~ollan,~.~:, Ehnholm,G. J., Gyl- ling,R.G. and Lounasmaa,O.V., J. Low Temp. Phys.

6 (1972) 357

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Cracknel1,M.F. and Wilson,G.V.H., Proc. Roy.

Soc. (1966) 71

/2/ Kamper,R.A. and Zimmerman,J.E., J. Appl. Phys.

42(1971) 132

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/3/ Marshak,H. and Soulen,R.J.,Jr., in Proc. 13th Int'l Conf. on Low Temp. Phys. Ed. K.D. Timmer- hause,W.J., O'Sullivan and E.F. Hammel (Plenum Publishing Co., 1974) Vol. 4,498

/4/ Soulen,R.J.Jr. and Marshak,H., in Proc. 14th Int'l Conf. on Low Temp. Phys., ed. M. Krusium and M. Vuorio (North-Holland, Amsterdam,l975) Vol. 4 p. 60.

/5/ Soulen,R.J.Jr. and Giffard,R.P., to be published /6/ Zech, E., Hagn, E., Ernst, H., and Eska in

E .

4th Int'l Conf. on Hyperfine Interactions, Ma- dison, N.J. (1977), to be published.