# Comparison of the Argon Triple-Point Temperature in Small Cells of Different Construction

- 489 Downloads

**Part of the following topical collections:**

## Abstract

The argon triple point (\(T_{90} = 83.8058\,\hbox {K}\)) is a fixed point of the International Temperature Scale of Preston-Thomas (Metrologia 27:3, 1990). Cells for realization of the fixed point have been manufactured by several European metrology institutes (Pavese in Metrologia 14:93, 1978; Pavese et al. in Temperature, part 1, American Institute of Physics, College Park, 2003; Hermier et al. in Temperature, part 1, American Institute of Physics, College Park, 2003; Pavese and Beciet in Modern gas-based temperature and pressure measurement, Springer, New York, 2013). The Institute of Low Temperature and Structure Research has in its disposal a few argon cells of various constructions used for calibration of capsule-type standard platinum resistance thermometers (CSPRT) that were produced within 40 years. These cells differ in terms of mechanical design and thermal properties, as well as source of gas filling the cell. This paper presents data on differences between temperature values obtained during the realization of the triple point of argon in these cells. For determination of the temperature, a heat-pulse method was applied (Pavese and Beciet in Modern gas-based temperature and pressure measurement, Springer, New York, 2013). The comparisons were performed using three CSPRTs. The temperatures difference was determined in relation to a reference function \(W(T)=R(T_{90})/R(271.16\hbox {K})\) in order to avoid an impact of CSPRT resistance drift between measurements in the argon cells. Melting curves and uncertainty budgets of the measurements are given in the paper. A construction of measuring apparatus is also presented in this paper.

## Keywords

Argon triple point Comparison CSPRT ITS-90## 1 Introduction

The argon triple point (\(T_{90} = 83.8058\;\hbox {K}\)) is a definitional fixed point of the International Temperature Scale of 1990. For realization of the point, miniature cells that contained high-purity argon, under a high pressure near 10 MPa at room temperature, can be used [6]. The temperature of argon during the transition realization in the miniature cells is measured with CSPRTs. Various types of sealed cells were manufactured and implemented for the realization of the triple point of argon within 40 years in several metrology institutes. An internal construction and a filling method are the main differences between these devices. Five miniature argon sealed cells manufactured at different metrology institutes—IMGC/INRiM in Italy, BNM/LNE—LNE-Cnam (France) and VNIIFTRI (Russia) are currently used at INTiBS.

The temperature differences of the phase transition realized in these cells were determined during the experiment. The phase transition of argon was performed under nearly adiabatic conditions, using a home-made cryostat cooled with liquid nitrogen.

## 2 Argon Cells

The tested argon triple-point cells

Cell | Number | Manufacturer |
---|---|---|

I | E5Ar-2001 | IMGC-CNR (now is INRIM), Italy |

II | 3Ar-6-V-86 | |

III | Ar05/3 | BNM-INM (now is LNE-Cnam), France |

IV | Ar01-2 | |

V | 796 | VNIIFTRI, Russia |

The cells construction, suppliers of the gas used for filling the cell and the methods of filling were different. Some important details of the constructions are presented in Fig. 1.

Preliminary tests showed that all cells contain argon and the amount of the gas was sufficient to realize the fixed point correctly. In the case of cells I,III, IV and V, the copper heat exchangers for realization of a thermal contact between the cell and CSPRTs were made (see Fig. 1). The heaters made of a high-resistivity wire were attached to the heat exchangers (cells I and III) or to the cell wall (cells II, IV and V). The heater was used to increase the cell temperature up to the triple point after freezing of the argon. The heater controlled by an electronic system allows to melt the substance in a controlled manner by putting the energy in a form of heat pulses while realizing the phase transition.

For temperature measurements, the following CSPRTs were used: Tinsley no. 217987, CHINO RS158-05 and CHINO RS158-06. The temperature measurements in the cells I–IV were performed with three thermometers, and in the cell V, two thermometers only could be used because of the heat exchanger construction. The resistance of the thermometers was measured using the FLUKE 1595A Super-Thermometer ratio bridge. The Tinsley 25 \(\Omega \) resistor \(\hbox {R}_{\mathrm{S}}\), placed in a thermostat, was used as a standard resistor.

## 3 Experiment

*F*value was a mean of 200 measurements. During the measurement of each cell, the total amount of argon contained in a cell was melted up to the value \(F = 1\).

Then, the value \(R_{{\mathrm{T}}}\) for \(F= 0.5\) was taken to the further analysis.

*y*thermometer is defined as:

*y*CSPRT resistance in the

*x*-th cell and \(R_{\mathrm{Wmean,y}}\) stands for the mean resistance value of the

*y*CSPRT determined in all cells. The \(\hbox {d}T/\hbox {d}R\) value is the sensitivity of the platinum thermometers equal to 10 K/\(\Omega \) at the \(T_{\mathrm{TPAr}}\) temperature. Both values—\(R_{\mathrm{W,xy}}\) and \(R_{\mathrm{Wmean,y}}\)—were determined for \(F = 0.5\). The \(R_{\mathrm{W,xy}}\) and \(R_{\mathrm{Wmean,y}}\) values included the influence of the CSPRT drift. The \(R_{\mathrm{W,xy}}\) is defined as:

*y*CSPRT resistance in

*x*-th cell at \(T_{\mathrm{TPAr}}\). \(R_{\mathrm{y}}(T_{\mathrm{TPW}})\) is the

*y*CSPRT resistance at \(T_{\mathrm{TPW}}\) and \(R_{\mathrm{y,mean}}(T_{TPW})\) the mean

*y*CSPRT resistance in all cells, defined as:

\(\Delta T_{\mathrm{W}}\) value for the cells I–V

Cell | \(\Delta T_{\mathrm{W}}, \mathrm{mK}\) |
---|---|

I | 0.15 |

II | \(-\)0.16 |

III | 0.00 |

IV | \(-\)0.04 |

V | 0.00 |

\(\Delta T_{\mathrm{W}}\) uncertainty budgets for the cells I–V, component values in \(\upmu \hbox {K}\)

Uncertainty component | Cell | ||||
---|---|---|---|---|---|

I | II | III | IV | V | |

Static thermal effect | 50 | 15 | 22 | 20 | 15 |

Dynamic thermal effect | 5 | 5 | 10 | 5 | 10 |

Reproducibility of thermometer | 2 | 2 | 2 | 2 | 2 |

Determination of \(F = 0.5\) | 18 | 30 | 17 | 5 | 4 |

Measurement noise | 6 | 4 | 9 | 5 | 6 |

\(\hbox {R}_{\mathrm{s}}\) thermal drift | 4 | 4 | 4 | 4 | 4 |

Combined standard uncertainty | 54 | 35 | 31 | 22 | 20 |

## 4 Conclusion

The results presented in this paper refers to the argon triple-point cells of a different construction that were manufactured in three metrology institutes during last 40 years. Differences in the construction of the cells have a noticeable impact on their thermal resistance and in consequence have an influence on the static thermal effect uncertainty component. The maximum value of this component is observed for the cell I (E5Ar-2001). In the cell, a thermal contact between the thermometer and the cell is realized on a small surface.

The largest plateau width equal to 0.12 mK for *F* between 0.2 and 0.8 was observed in cell II. The smallest value (0.02 mK) was observed for cell V. This may be due to the fact that the cell was filled with the gas of the highest purity.

The maximum difference of the argon triple-point temperature realized in all cells was lower than 0.31 mK with standard uncertainty \(u(\Delta T) = 0.07\;\hbox {mK}\). Neither manufacturing date nor the method of filling of the cells affects a significant change in the temperature of the triple point. This confirms that the production process of all cells maintains appropriate technological conditions

## Notes

### Acknowledgements

The work was realized with a financial support of the National Centre of Research and Development NCBiR within the Grant PBS1/A9/6/2012.

## References

- 1.H. Preston-Thomas, Metrologia
**27**, 3 (1990)ADSCrossRefGoogle Scholar - 2.F. Pavese, Metrologia
**14**, 93 (1978)ADSCrossRefGoogle Scholar - 3.F. Pavese, D. Ferri, I. Peroni, A. Pugliese, P.P.M. Steur, B. Fellmuth, D. Head, L. Lipinski, A. Szmyrka-Grzebyk, L. Wolber,
*Temperature, part 1*, vol. 7 (American Institute of Physics, College Park, 2003)Google Scholar - 4.Y. Hermier, L. Pitre, C. Geneville, A. Verge, G. Bonnier, D.I. Head, B. Fellmuth, L. Wolber, A. Szmyrka-Grzebyk, L. Lipinski, M.J. de Groot, A. Peruzzi,
*Temperature, part 1*, vol. 7 (American Instistute of Physics, College Park, 2003)Google Scholar - 5.F. Pavese, G.M.M. Beciet,
*Modern Gas-Based Temperature and Pressure Measurement*, 2nd edn. (Springer, New York, 2013)CrossRefGoogle Scholar - 6.F. Sparasci, L. Pitre, G. Rouillé, J.-P. Thermeau, D. Truong, F. Galet, Y. Hermier, Int. J. Thermophys.
**32**, 201 (2011)ADSCrossRefGoogle Scholar - 7.A. Szmyrka-Grzebyk, L. Lipiński, H. Manuszkiewicz, A. Kowal, A. Grykałowska, D. Jancewicz, Int. J. Thermophys.
**32**, 2466 (2011)ADSCrossRefGoogle Scholar - 8.D.R. White et al., Uncertainties in the Realisation of the SPRT Subranges of the ITS-90, CCT/08-19/rev, CCT WG3: July 2009, http://www.bipm.org/cc/CCT/Allowed/24/D19_rev_WG3_Doc_rev_10July2009.pdf

## Copyright information

**Open Access**This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.