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Publication Citation: Temperature stabilization system with millikelvin gradients for refractometry

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Author(s): Patrick F. Egan; Jack A. Stone Jr.;
Title: Temperature stabilization system with millikelvin gradients for refractometry
Published: July 25, 2010
Abstract: Refractometry of air is a central problem for interferometer-based dimensional measurements. Refractometry at the 10^{-9} level is only valid if air temperature gradients are controlled at the millikelvin level. Very precise tests of second-generation NIST refractometers involve comparing two instruments (two optical cavities made from ultralow expansion glass) that are located in nominally the same environment; temperature gradients must be kept below a few millikelvin to achieve satisfactory precision of these tests. In this paper we describe a thermal stabilization scheme that maintains < 1 mK thermal gradients over 100 hours in a 0.5 m x 0.15 m x 0.15 m volume. Our approach uses passive (aluminum envelopes and foam insulation) and active (thermistors, foil heaters, and PID control) temperature stabilization. Thermal gradients are sensed with thermocouples and a nanovoltmeter and switch; the reference junctions of the thermocouples being in thermal contact with a thermistor temperature standard. Our < 1 mK gradient performance is limited by the accuracy of the nanovoltmeter and switch.
Conference: 2010 NCSL International Workshop and Symposium: 21st Century Innovations in Metrology
Proceedings: 2010 NCSL International Workshop and Symposium
Pages: 10 pp.
Location: Providence, RI
Dates: July 25-29, 2010
Keywords: Temperature stabilization, Refractometry, Thermometry
Research Areas: Thermometry, Instrumentation, Length
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