1. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Realisation of ITS-90 fixed points and associated uncertainties Bernard ROUGIE, Mohamed SADLI ( BNM-INM)

2. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Introduction Black body and furnace technology Sources of uncertainty Uncertainty budget : ITS-90 and beyond

3. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Heating element : Ni-Cr-Al (Kanthal), max. temperature 1300 °C Technology : 3-zone furnace associated to three temperature controllers Temperature sensors : 3 Type S thermocouples Temperature stability < 0.1 °C Temperature uniformity < 0.3 °C over 80 mm (in the central region of the furnace) Furnace characteristics

4. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Material : High-purity (5N) graphite. Machining by especially dedicated tools (in order to minimize pollution) Dimensions : Solidity ensured by a “rounded” design of the inner edges of the most fragile parts. Additional parts (screw or ring) to support the cavity well from hydrostatic force. Wall thickness of the cavity is 0.9 mm. 1 mm 8 mm 90 mm 35 mm 75 mm Crucible dimentions

5. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 43 mm 700 mm Copper, gold or siver Realisation of ITS-90

6. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Crucible filling-up set-up Silver 0.515 kg Gold 0.952 kg Copper 0.422 kg

7. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Radiance comparator Aperture stop Detectors Field stop Grating Other source Black body Sources bench

8. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Analysis of gold test piece Measured from a spark spectrum Global purity : 0.99985

9. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Impurities State of the art estimate for the uncertainty components caused by impurities and isotopes B. Fellmuth, J. Fischer, E..Tegeler –Basis of the estimates: –Standard deviations of the results near (CCT-k2) or at fixed points (CCT-K3, CCT K4) of the CIPM Key comparisons Fixed points Ga In Sn Zn Al Ag Estimate (mK) 0.2 0.8 0.5 0.7 1.5 4 Proposal : These guideline estimates should be used for uncertainty budgets if State-of-the-art high purity materials are used and no individual information on the impurity content is available.

10. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Emissivity : Parameters and uncertainty

11. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Temperature gradient through crucible wall Heat flow is constant at each point : wall thickness, inner temperature and outer temperature are uniform; radiation loss is uniform at each point The solid angle of emission is determined by the output diaphragm of the cavity and the first diaphragm in front of it which is almost at the same temperature Heat loss through output diaphragm is only due to radiation (no convection). It is computed by Stefan law. Metal at uniform temperature 75 mm  =0.05 sr 9 mm Sout =8 mm or 1 mm Sint :internal surface

12. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Computation of temperature drop Sout : output surface Sint : internal surface e : wall thickness R th : thermal resistivity  0 : flux lost through cavity wall

13. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Value and uncertainty of temperature drop

14. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Temperature uniformity

15. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Freezing and melting plateau

16. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Uncertainty budget ITS-90 fixed points

17. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Future High temperature fixed points T=2600 K Uncertainty budget

18. Workshop on uncertainties in radiation thermometry Paris,September 7, 2001 Conclusion The major component of ITS-90 fixed points uncertainty is due to the plateau determination and its reproducibility. –Improvements of temperature uniformity can reduce this term to 10 mK. The influence of metal purity is not easy to evaluate but not negligible. For the higher temperature fixed points, the gradient of temperature through cavity wall will be to evaluate accurately.