Fluorescence temperature sensing on rotating samples in the cryogenic range

A surface temperature measurement technique for rotating samples is propose d. It is based on the concept of fluorescence thermometry. The fluorescent and phosphorescent phenomena have been applied in thermometry for ambient a nd high-temperature measurement but not the cryogenic domain, which is expl ored using thermocouple- or platinum resistor-based thermometers. However, thermal behavior of Yb2+ ions in fluoride matrices seems to be interesting for thermometry in the range 20-120 K. We present here a remote sensing met hod which uses fluorescence behavior of Yb2+ ion-doped fluoride crystals. T he fluorescence decay time of such crystals is related to its temperature. Since we developed a specific sol-gel process (OrMoSils) to make strongly a dherent fluorescent layers, we applied the fluorescence thermometry method for rotating object surface temperature measurement. The main application i s the monitoring of surface temperature of the ball bearing or turbopump ax is in liquid propulsion rocket engines. Our method is presented and discuss ed, and we give some experimental results. An accurate calibration of the d ecay time of CaF2:Yb2+ versus temperature is also given. (C) 1999 American Institute of Physics. [S0034-6748(99)04107-6].