Carbon Resistance Thermometers Research Articles

A Reexamination of Phonon Transport Through a Nanoscale Point Contact in Vacuum

Using a silicon nitride cantilever with an integral silicon tip and a microfabricated platinum–carbon resistance thermometer located close to the tip, a method is developed to concurrently measure both the heat transfer through and adhesion energy of a nanoscale point contact formed between the sharp silicon tip and a silicon substrate in an ultrahigh vacuum atomic force microscope at near room temperature. Several models are used to evaluate the contact area critical for interpreting the interfacial resistance. Near field-thermal radiation conductance was found to be negligible compared to the measured interface thermal conductance determined based on the possible contact area range. If the largest possible contact area is assumed, the obtained thermal interface contact resistance can be explained by a nanoconstriction model that allows the transmission of phonons from the whole Brillouin zone of bulk Si with an average finite transmissivity larger than 0.125. In addition, an examination of the quantum thermal conductance expression suggests the inaccuracy of such a model for explaining measurement results obtained at above room temperature.

Characteristics of russian carbon resistance (TVO) cryogenic thermometers

As part of an effort to identify suitable thermometers for use in the Superconducting Super Collider, a sample of the Russian TVO carbon resistance thermometers were evaluated by the SSC Laboratory. The tests included recalibrating the thermometers and including them in a gamma irradiation experiment performed at Ohio State University. This paper uses both Russian and SSC data to describe the characteristics of the thermometers. The construction and calibration of the TVO resistors is also discussed. The thermometers are found to have properties that make them an attractive low cost option for certain cryogenic applications.

The thermometric properties of MODEL RS-11 Chinese carbon resistors at low temperatures and in magnetic fields

The resistance-temperature relationship and self-heating characteristics of encapsulated RS-11 carbon resistors from the People’s Republic of China demonstrate their suitability as thermometers for the temperature range 1–30 K. A simple interpolation method for them is accurate to 10 mK while polynomial fitting will give 1-mK precision. At 20 K their stability over 30 thermal cycles is typically of the order of 0.1 K, superior to commercially available cryogenic carbon resistance thermometers although inferior to carbon-glass thermometers. These resistors are useful in magnetic fields. At 4.2 K at field intensities up to 10 T, their magnetic field-dependent temperature error is no greater than 5%, and they show no orientation effect.

Carbon resistance thermometers and variable-range hopping

Abstract The observed temperature dependence of a wide variety of carbon resistance thermometers is compared with the simple models of variable-range hopping. It is shown that for some resistors at very low temperatures, the 1/3-power law (for hopping in 2 D) provides a slightly more accurate fit than the 1/4-power law (for hopping in 3 D). In other cases, the two power laws are indistinguishable within the accuracy of the data.

Magnetic behavior of nonet tetracarbene as a model for one-dimensional organic ferromagnets

Magnetic behavior of nonet tetracarbene as a model for one-dimensional organic ferromagnets

Cryogenic Neutron Calorimeter for and ICF Test Facility

This paper proposes a new technique for measuring the neutron yield from ICF test facilities and other neutron facilities in situ. The technique employs the temperature increase by neutron heating of material cooled to below 4 K, where the specific heat decreases drastically. In materials (graphite, Be, B, Cu, U and Si) cooled to 2 K and placed 10 cm from a fusion pellet (1012 n/shot), the temperature increase is found to be 0.74 K, 0.77 K, 4.15 K, 0.17 K, 0.82 K and 2.05 K respectively. These temperature increases are ∼104∼5 times as large as those at room temperature and are measurable by a carbon resistance thermometer. The neutron yield can be calculated from the temperature increase of the materials.

An experimental test of acoustical reciprocity calibration applied to thermal transducers in superfluid helium

An experiment will be described which has verified an extension of the reciprocity calibration technique to reversible thermal transducers in superfluid helium. A plane‐wave resonator of circular cross section was capped at both ends by reversible teflon electret diaphrams which contained many razor slits to generate or detect thermal waves (second sound). The resonator also incorporated a thermophone and a dc biased carbon resistance thermometer to set independent upper and lower limits on the amplitude of the temperature oscillations within the resonator. The acoustical resonance data was acquired and analyzed by a computer controlled system described previously [D. V. Conte and S. L. Garrett, J. Acoust. Soc. Am. Suppl. 1 72, S82 (1982)]. The temperature excursions measured by the reciprocity method fell between the upper and lower limits which, for lower modes, were separated by only a few percent. At higher modes the lower limit departed from the upper limit due to the thermal inertia of the resistance thermometer. Temperature excursions smaller than 10−8 °K/[(Hz)1/2] were detectable using the electret transducers and a pre‐amplifier with a noise floor of 10−8 V/[(Hz)1/2]. [Work supported by the NPS Foundation Research Program.]

Stability of some cryogenic carbon resistance thermometers

The stability of 12 commercial carbon resistance thermometers has been tested at three temperatures, 12.6, 20.3, and 30 K, when the sensors were exposed to cycling between 12.6 and 293 K. The resistances of the thermometers changed markedly over 20 such cycles by amounts equivalent to temperature changes of between 0.07 and 0.57 K at 20.3 K. Both abrupt and gradual changes were observed. A few measurements were made at 4.2 K to explore the correlation between changes in resistance at various temperatures. A two-point recalibration method is shown to be accurate to 1 mK over the range 12.6 to 30 K and can be used to 4.2 K.

A carbon resistance thermometer with fast response below 10 mk

An electromagnetically shielded carbon thermometer is described. The unit has a response time shorter than the thermal equilibration time of the cryosystem at 5 mK: of the order of 5 min.

Electron tunnelling in carbon resistance thermometers

It is proposed that the mechanism of electrical conduction in carbon thermometers is similar to that in granular metals studied by Ping Sheng et al : the number of charged grains is thermally activated owing to the electrostatic energy required to form charged pairs, and electrons move from grain to grain by quantum-mechanical tunnelling.

Millikelvin temperature thermocouple

Abstract A Au FeNbTi thermocouple thermometer has been developed and used to measure temperature from 20 mK to 7.0 K. High sensitivity is achieved with the use of superconducting circuits and a SQUID amplifier. The performance of the thermocouple is found to be quite satisfactory with about a 1000 times more temperature resolution between 20 mK and 50 mK than conventional carbon resistance thermometers.

Ultrasonically enhanced heat transfer in liquid helium

The effects of 10‐MHz ultrasound on heat transfer from a copper block in liquid helium were studied as a function of temperature and acoustic amplitude. The copper block was mounted in the dewar system with a PZT‐4 10‐MHz thickness‐mode resonant transducer positioned perpendicular to its surface. The temperature of the solid was determined using carbon resistance thermometers whose resistance was measured with ac bridge and lock‐in amplifier circuitry. A heater in the copper block was supplied with current to give heat fluxes in the range from 0 to 1.5 mW/cm2. Measurements were made for temperature differences up to 50 mK. In Hell for the temperature range from 1.4 to 1.6 K, the ultrasound had no effect on heat transfer from the sample for amplitudes up to the threshold for collapse cavitation. In contrast, ultrasound produces a significant increase in heat transfer in Heɪ. At a temperature of 2.64 K the effective thermal conductance increased linearly with increasing acoustic velocity amplitude reaching a value which was approximately 2.5 times that of the nonsonated values for a velocity amplitude of 0.8 cm/s. [The work was supported in part by the Air Force Office of Scientific Research.]

Some carbon resistance thermometers in low magnetic fields

The magnetoresistance in the liquid helium temperature range has been determined for a number of Ohmite/Allen–Bradley 1/8 W and older Allen–Bradley 1/10 W resistors in magnetic fields from 0.01 to 0.1 T. The new resistors show ΔR/R∝B1.3±0.2; the older resistors show negative ΔR/R over a large part of this field range. Both sets show larger fractional changes at higher temperatures. The apparent fractional temperature shifts are also given for typical resistors when used as thermometers.

Magnetic-field-induced temperature error of some low-temperature thermometers

The effect of high magnetic fields (up to 18.4T) on germanium, platinum and carbon resistance thermometers and SrTiO3 capacitive thermometers has been investigated in the temperature range from 2-87K. Figures are presented which allow a crude estimate of the real temperature if these thermometers are read under high-field conditions.

Heat capacity of Matsushita carbon resistance thermometers below 1 K

Matsushita resistors have a much smaller heat capacity than Speer resistors, and thus are preferable in some thermometry applications at temperatures below 1 K.

A pumped supercritical helium flow loop for heat transfer studies

The construction and operation of a flow loop is described in which a 0.5 ls − centrifugal pump circulates supercritical helium through a 1 m long, 18 mm id heated test section instrumented with 18 carbon resistance thermometers. Based on the heat transfer measurements obtained (published in detail elsewhere) some observations are made on deviations from the standard Dittus Boelter heat transfer correlation caused by helium's variable properties, and on possible buoyancy induced reductions in heat transfer particularly for radially inward flow in rotating machines.

A low temperature calibration equation for carbon resistance thermometers in high magnetic fields

An interpolation equation for a 470 Omega , 0.5 W Speer resistor has been found, which with 20 calibration points enables an interpolation accuracy of better than 3 mK to be obtained in the range 0.3-4 K and in magnetic fields of up to 6.5 T.

A simple low power self-balancing resistance bridge

The design of a simple self-balancing AC resistance bridge with digital readout is discussed. The instrument operates with an extremely small power dissipation in the unknown, and is particularly suitable for use with carbon resistance thermometers at low temperatures. An accuracy exceeding 0.5% is obtained over the range 20 Omega to 2M Omega .

Time response and thermal diffusivity of carbon resistance thermometers

The time response of several carbon resistance thermometers has been measured in the liquid helium temperature range. The results are compared to the theoretical analysis of Komatsu and are found to be in fair agreement. The data indicate that carbon resistors have an intrinsic time response of the order of milliseconds. However, this probably would be increased considerably due to contact resistance if the resistor were coupled to a solid surface.

Alternating Current Losses in Thin Film Superconductors: New Calorimetric Measurement Technique

A calorimetric technique has been developed for measuring the ac loss in short, cylindrical thin film superconductors carrying a transport current. Substrates used in the present study were 0.32 cm in diameter by 3.8 cm long. Loss in the range 10−8−10−4 W may be determined by measuring the temperature rise at the center of the sample, which causes a decrease in resistance of a carbon resistance thermometer mounted inside the hollow cylindrical substrate on which the superconductor is deposited. By maintaining the current contacts at 4.2 K and heating the center of the sample (in a vacuum can), loss may be determined from 4.2 K up to the transition temperature of the superconductor. Data below 4.2 K are taken by lowering the temperature of the coolant bath. This technique has been used extensively to study the temperature dependent ac properties of Nb3Sn. Typical loss data are shown.