Quantitative atomic spectroscopy for primary thermometry

Quantitative spectroscopy has been used to measure accurately the Doppler-broadening of atomic transitions in $^{85}$Rb vapor. By using a conventional platinum resistance thermometer and the Doppler thermometry technique, we were able to determine $k_B$ with a relative uncertainty of $4.1\times 10^{-4}$, and with a deviation of $2.7\times 10^{-4}$ from the expected value. Our experiment, using an effusive vapour, departs significantly from other Doppler-broadened thermometry (DBT) techniques, which rely on weakly absorbing molecules in a diffusive regime. In these circumstances, very different systematic effects such as magnetic sensitivity and optical pumping are dominant. Using the model developed recently by Stace and Luiten, we estimate the perturbation due to optical pumping of the measured $k_B$ value was less than $4\times 10^{-6}$. The effects of optical pumping on atomic and molecular DBT experiments is mapped over a wide range of beam size and saturation intensity, indicating possible avenues for improvement. We also compare the line-broadening mechanisms, windows of operation and detection limits of some recent DBT experiments

Ultrasonic measurement of core material temperature, phase 2

Sheaths for pulse-echo ultrasonic temperature senso

ARCADE: Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission

The Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE) is a balloon-borne instrument designed to measure the temperature of the cosmic microwave background at centimeter wavelengths. ARCADE searches for deviations from a blackbody spectrum resulting from energy releases in the early universe. Long-wavelength distortions in the CMB spectrum are expected in all viable cosmological models. Detecting these distortions or showing that they do not exist is an important step for understanding the early universe. We describe the ARCADE instrument design, current status, and future plans.Comment: 12 pages, 6 figures. Proceedings of the Fundamental Physics With CMB workshop, UC Irvine, March 23-25, 2006, to be published in New Astronomy Review

Dry Dilution Refrigerator with He-4 Precool Loop

He-3/He-4 dilution refrigerators (DR) are very common in sub-Kelvin temperature research. We describe a pulse tube precooled DR where a separate He-4 circuit condenses the He-3 of the dilution loop. Whereas in our previous work the dilution circuit and the He-4 circuit were separate, we show how the two circuits can be combined. Originally, the He-4 loop with a base temperature of ~ 1 K was installed to make an additional cooling power of up to 100 mW available to cool cold amplifiers and electrical lines. In the new design, the dilution circuit is run through a heat exchanger in the vessel of the He-4 circuit so that the condensation of the He-3 stream of the DR is done by the He-4 stage. A much reduced condensation time (factor of 2) of the He-3/He-4 gas mixture at the beginning of an experiment is achieved. A compressor is no longer needed with the DR as the condensation pressure remains below atmospheric pressure at all times; thus the risk of losing expensive He-3 gas is small. The performance of the DR has been improved compared to previous work: The base temperature of the mixing chamber at a small He-3 flow rate is now 4.1 mK; at the highest He-3 flow rate of 1.2 mmol/s this temperature increases to 13 mK. Mixing chamber temperatures were measured with a cerium magnesium nitrate (CMN) thermometer which was calibrated with a superconducting fixed point device.Comment: Cryogenic Engineering Conference 201

Micro- and Nanoscale Measurement Methods for Phase Change Heat Transfer on Planar and Structured Surfaces

In this opinion piece, we discuss recent advances in experimental methods for characterizing phase change heat transfer. We begin with a survey of techniques for high-resolution measurements of temperature and heat flux at the solid surface and in the working fluid. Next, we focus on diagnostic tools for boiling heat transfer and describe techniques for visualizing the temperature and velocity fields, as well as measurements at the single bubble level. Finally, we discuss techniques to probe the kinetics of vapor formation within a few molecular layers of the interface. We conclude with our outlook for future progress in experimental methods for phase change heat transfer.United States. Dept. of Energy (Advanced Research Projects Agency-Energy Grant DE-AR0000363)National Science Foundation (U.S.) (Grant 1261824)United States. Office of Naval Research (Grant N00014-13-1-0324

Design of an adiabatic demagnetization refrigerator for studies in astrophysics

An adiabatic demagnetization refrigerator was designed for cooling infrared bolometers for studies in astrophysics and aeronomy. The design was tailored to the requirements of a Shuttle sortie experiment. The refrigerator should be capable of maintaining three bolometers at 0.1 K with a 90% cycle. The advantage are of operations the bolometer at 0.1K. greater sensitivity, faster response time, and the ability to use larger bolometer elements without compromising the response time. The design presented is the first complete design of an ADR intended for use in space. The most important of these specifications are to survive a Shuttle launch, to operate with 1.5 K - 2.0 K space-pumped liquid helium as a heat sink, to have a 90% duty cycle, and to be highly efficient

Practical Doppler broadening thermometry

We report initial research to develop a compact and practical primary thermometer based on Doppler broadening thermometry (DBT). The DBT sensor uses an intrinsic property of thermalized atoms, namely, the Doppler width of a spectral line characteristic of the atoms being probed. The DBT sensor, being founded on a primary thermometry approach, requires no calibration or reference, and so in principle could achieve reliable long-term in-situ thermodynamic temperature measurement. Here we describe our approach and report on initial proof-of-concept investigations with alkali metal vapour cells. Our focus is to develop long-term stable thermometers based on DBT that can be used to reliably measure temperatures for long periods and in environments where sensor retrieval for re-calibration is impractical such as in nuclear waste storage facilities.Comment: 7 pages, 4 figures, referees' comments incorporate