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Submitted on 1 Jan 1984
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PRESSURE SENSOR FOR LOW TEMPERATURE USE
D. Fabre, M. Thiéry
To cite this version:
D. Fabre, M. Thiéry. PRESSURE SENSOR FOR LOW TEMPERATURE USE. Journal de Physique
Colloques, 1984, 45 (C8), pp.C8-405-C8-406. �10.1051/jphyscol:1984873�. �jpa-00224375�
JOURNAL DE PHYSIQUE
Colloque C8, supplement an n ° l l , Tome *5, novembre 198^ page C8-405
PRESSURE SENSOR FOR LOW TEMPERATURE USE
D. Fabre and M.M. Thiery
Taboratoire dee Inteva.ati.ono Moleoulaives et des f/o.utes Press-ions, CNRS, Vniversite Paris-Nopd, 93430 Villetaneuse, Finance
Abstract - The fluorescence of a titanium doped sapphire crystal is used in low temperature experiments as a pressure sensor up to 13 kbar. With increa- sing pressure, the two zero phonon lines of the Ti' ion show a linear blue shift in the investigated pressure range; the pressure coefficients are 7.9 and 7.8 t 0.3 cm"1 kbar"1 at 4K, and, 8.5 and 8.41 0.2 cm"1 kbar"1 at 77K.
Pressure is commonly determined in optical pressure cells by measuring the pressure shift of the R fluorescence lines of a ruby chip placed in the cell /1/.The pressure coefficient was also determined at low temperature by Noack and Holzapfel / 2 / and in our laboratory. At 4K, only the R.. line is observed; due to its small width at 4K, the R line frequency can be measured accurately; however, a random shift of the 1 bar reference frequency, related to optical aberration errors and imperfectly controlled geometrical conditions, is often observed; this shift is independent of the pressure and, with a pressure coefficient of 0.76 an kbar results in an additional incertitude of 5 or 600 bar, since one cannot be sure of mechanical reproducibility between the 1 bar and the high pressure scans. The influence on a pressure measurement of the additional incertitude of t 0.5 cm will be reduced if the pressure sensor is a fluorescing material whose pressure coefficient is much higher than that of ruby (in absolute value); this is the case of the titanium doped sapphire. The two lines used, T. and 'l\> around 16179 and 16217 cm (i.e. around 6179 and 6165 A ) at 1 bar and 4K (F.ig.1), occur on the high energy side of a broad and intense fluorescence band due to electronic transitions of the Ti ion in A170,, /3/. They correspond to zero nhonon transitions and appear veiy clearly at 4K;
they are still observed at 77K, but they are broader and superimposed on the increa- sing continuum background; they are no longer detected at room temperature. There- fore, their use is limited to low temperature experiments. Their blue shift due to the pressure is by far higher than the corresponding red shift of the R lines.
The CALIBRATION PROCEDURE and DISCUSSION are reported in a recent paper published in REVUE de PHYSIQUE APPLIQUEE, 1984.
RESULTS
'Hie pressure coefficients of the T lines, at 4.2K and 77K, obtained from the linear pressure calibration curves, are displayed in table 1 and compared to the ruby Ri coefficient obtained at 4.2K by the same method /4-6/. The T pressure coefficients are higher than the Ri pressure coefficient by an order of magnitude; however, the
Résume - On a utilise pour mesurer la pression jusqu'à 13 kbar, à basse température, la fluorescence d'un cristal de saphir dope au titane. Les deux raies utilisées correspondent à des transitions purement électroniques de 1' ion titane; leur déplacement vers le bleu, avec la pression, est de 7,9 et 7,8 ± 0,3 cm"1 kbar"1 à 4K, et, de 8,5 et 8,4 ± 0,2 cm"1 kbar"1 à 77K.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984873
JOURNAL DE PHYSIQUE
Curve a
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1 bar, 77K Curve b - 1 bar, 4.2K Curve c - 7 kbar, 4.2K( peak heights are arbitrary )
Fig.1
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Typical spectra of titanium doped sapphire with 450 ppm concentration. The small feature at 16197 cm-' is a fluorescence line of the laser plasma.T lines are broader than the R line, resulting in similar "figure of merit" as defined in /I/; but, due to the possible drift of the wavenumber scale, independent of the sensor nature and of the pressure, it is advisable to rather use the T lines, spe- cially at moderate pressures; indeed, a frequency scale shift resulting in an addi- tional error of 600 bar in the case of ruby, will produce an error of 60 bar only, if a Ti doped sensor is used; in such a case, the time consuming and expensive 1 bar reference measurement can even be neglect.ed in a pressure estimation.
Table I
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Pressure coefficients of the ~i~~ ion T lines and of the ruby R1 line at 77 K and 4.2 K; a) our measurement. b) reference / 2 / .In conclusion, at least up to 15 kbar and below 80K, the titanium doped sapphire, A1203(Ti ),is a suitable pressure sensor. 3+
Acknowledgments
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The authors like to thank the "Soci6t6 CRICERAM", filiale"PECHINEY", (department "Le Rubis Synthetique des Alpes") for kindly providing them with titanyan doped crystal samples.
References
I/ BARNETT, J.D., BLOCK,S. and PIEWjlARINI,G.J., Rev. Sci. Instrum. 44 (1973) 1.
2/ NOACK,R.A. and HOLZAPFEL, W. B.
,
Proceedings of the Sixth A I M international conference, edited by TIMERHAUS,K.D. and BARBER, EI.S.,(Plenum, New-York, 1979).3/ &C~ER,B.F. and KONINGSTEIN,J.A., J. Chem. Phys. 60 (1974) 2003.
4/ STEWT,J.W., J. Phys. Chem. Solids, 1 (1956) 146.
5/ FABRE, D., THI&.Y, M.M. and VODAR, B.,C.R. Acad. Sci. Ser. B, 280 (1975) 781.
6/ FABRE, D., High temp.
