Cryogenic Thermometers Research Articles

High resolution cryogenic quartz thermometer and application towireless measurement

The high quality synthetic single crystal quartz resonator mounted in a casing of 3 mm diameter with 8 mm length has been developed for the cryogenic temperature sensor covering with the wide range from 400 K to 4.2 K under thickness shear mode operation about 28 MHz through either extended cable connection or wireless radio echo telemetric transmission from the resonator. A wireless echo sensor system of quartz cryogenic temperature sensor system has been constructed and tested for an application to cryogenic temperature control.

The manufacture of a cryogenic silicon diode thermometer and its application in a temperature controlling system

According to characteristics of temperature dependence of the forward voltage of silicon diode with a constant current supply the manufacture of the planar silicon transistor base-collector junction diode as cryogenic thermometers was carried out in Xi'an. The results of its performance tests at temperatures down to 1.6K are reported. By using it as a temperature sensor in a cryogenic temperature controlling system the precision of controlled temperatures is improved from 0.5 K to 0.01 K. The constructed temperature auto-controlling system could use a variety of types of thermometers as its temperature sensor with a signal output at voltage level of 0 – 3.2 v.

Granular nickel films as cryogenic thermometers

We have used RF sputtering to prepare a series of granular Ni x (SiO 2) 100− x films with nickel concentrations, x, between 60 and 90 atomic percent. The electrical resistivity of such films depends strongly on composition. We find that films with about 65 percent Ni have a temperature dependence suitable for use as cryogenic temperature sensors down to at least 100 mK. In addition, these films are relatively insensitive to magnetic fields. The largest resistance change we measured was about 1.5% in a field of 6 T at 200 mK, corresponding to a 4% temperature shift.

Granular nickel films as cryogenic thermometers

We have used RF sputtering to prepare a series of granular Ni x (SiO 2 ) 100− x films with nickel concentrations, x, between 60 and 90 atomic percent. The electrical resistivity of such films depends strongly on composition. We find that films with about 65 percent Ni have a temperature dependence suitable for use as cryogenic temperature sensors down to at least 100 mK. In addition, these films are relatively insensitive to magnetic fields. The largest resistance change we measured was about 1.5% in a field of 6 T at 200 mK, corresponding to a 4% temperature shift.

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.

Good performance of two kinds of cryogenic film-type thermometers after exposure to 10 7 Gy of ionizing radiation and in magnetic fields of up to 7 T at 4.2 K

The resistance versus temperature characteristics between 4.2 and 300 K of two kinds of amorphous temperature sensors, a vacuum deposited carbon type and a ruthenium oxide thick-film type, were measured before and after irradiation with 3 MeV electrons to a dose up to 10 7 Gy. Only very small changes were observed. For both types of sensors the magnetoresistance effect at 4.2 K and at field strengths up to 7 T did not depend on the field direction. The apparent change of temperature at 4.2 K of the carbon type sensors was about −0.13 K at 7 T, whereas this effect was of the order of − 0.05 K for the thick-film type sensor. Advantages of the carbon sensor at 4.2 K are a six times larger value of the sensitivity dR R dT and a somewhat better reproducibility and mechanical stability.

Electrical properties of polyimide films implanted with nitrogen and argon

Electrical properties have been studied for polyimide films implanted with nitrogen and argon ions in order to examine their applicability to a cryogenic thermometer. The resistivity was measured down to liquid helium temperature. Effects of ion implantation on the resistivity of polyimide have been investigated under the following conditions: ion species: nitrogen and argon; voltage: 50–90 keV; dose: 5 × 10 16−5 × 10 17cm −2; current density: 2.6 × 10.2 |μA/cm 2; multistep implantation; and ion mix Ag. The resistivity of all implanted films was increased with decreasing temperature. It was found that the resistivity decreased with increasing energy and dose. A slight current density effect was found. The ion mixing with Ag and multistep implantation also reduced the resistivity. Effects of thermal cycling and magnetic field have also been investigated. It was found that the effect of thermal cycling up to 100 cycles was negligible.

New type cryogenic thermometer using sputtered Zr-N films

A new type thin-film thermometer using sputtered Zr-N films especially for cryogenic temperature range has been developed. Zr-N thermometers have high sensitivity in a wide temperature region from 300 to 2 K or even lower, and have a response quick enough to detect the second sound in superfluid helium. It is found that the developed thermometers are insensitive to magnetic field. Temperature error induced by application of magnetic field up to 6 T is only less than 4.5 mK at 4.2 K.

Thin Film Thermometer for Cryogenic Temperature

A new type of cryogenic thermometer using sputtered zirconium nitride film has been developed. The sensor was integrated on a sapphire substrate by reactive sputtering equipment, and its sensing area was only 1 mm long and 2 mm wide. The thin film sensor has wide sensitive region from 300 to 2 K, or even lower and fast response time to detect second sound in superfluid helium. Magnetic field dependence of the sensor is small. Under the magnetic field of 6 T, the magnetoresistance was smaller by two orders of magnitude than that of carbon-glass resistance thermometer at 4.2 K. The effect of the longitudinal magnetic field of 6 T to temperature is less than 5 mK.

Russian germanium resistance thermometers at low temperatures in magnetic fields

A type of germanium resistance thermometer manufactured at the Semiconductor Institute, Kiev, USSR, displays much lower magnetoresistive effects than most other types of cryogenic semiconductor resistance thermometers. Measurements are reported on the temperature dependence of the electrical resistance of these thermometers (1.5–30 K at zero magnetic field) and their zero-field stability when exposed to thermal cycling between 20 and 288 K.

A cryogenic fast response thermometer

Multipurpose carbon thin film resistance thermometers have been developed for cryogenic use. Carbon was electron beam evaporated onto polycrystalline alumina substrates with copper films as electrical contacts. The thermometers were coated with thin glass layers. The desired electrical resistance of the sensors was obtained with a final heat treatment. Their sensitivity at 4.2 K is approximately 300 Ω K −1. Between 4.2 and 20 K the film resistance can be expressed as a function of temperature by a usual correlation of the form In R = A 0 + A 1 T + A 2 ( In T) 2. These sensors have been developed as separate devices to be soldered or glued onto experiments. Nevertheless, their response is fast; at 4.2 K their thermal relaxation time is better than 1 ms and their thermal delay time is of the order of 70 μs.

Behaviour of semiconductor low temperature sensors in electromagnetic environments

The effect of an electromagnetic field, with frequencies in the 30 – 300 MHz range, on semiconductor cryogenic thermometers, eg silicon diode temperature sensors as well as silicon and germanium resistance thermometers, has been investigated at temperatures from 70 to 300 K. The changes in voltage drop or resistance versus temperature characteristics of the tested thermometers for various fixed frequencies of external electromagnetic field have been found. The frequency dependent electromagnetic field behaviour of the thermometers was studied and a resonance character of the ‘error’ ΔT has been evaluated. It has been shown that the semiconductor low temperature sensors may only be used for accurate recalibration in the presence of a well-known, low-intensity EM field at a constantly held frequency not corresponding with the maximum values of ΔT.

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.

Gallium arsenide phosphide light-emitting diodes as general thermometers above 35 K

It is shown that Monsanto MV54 light-emitting diodes can be mounted in the ‘‘as received’’ condition so as to serve as cheap, sensitive, and reliable cryogenic thermometers.

The interpolation of germanium and carbon cryogenic thermometer calibrations

Some tests on the accuracy of simple interpolation routines applied to cryogenic resistance thermometer calibrations are described. Interpolation accuracy is found to be limited almost entirely by experimental scatter in the original calibration. When only a small number of calibration points is available the simple methods give far greater accuracy than is possible using polynomial regression.

Recent Advances in Cryogenic Thermometry

The recent availability of a linear resistance thermometer makes possible a simple direct-reading cryogenic thermometer, which does not require calibration charts or linearization networks. Another instrument for cryogenic thermometry is also described. This is a semiautomatic mutual inductance bridge developed specifically for paramagnetic thermometry. This bridge enables greater accuracy and speed of operation than earlier techniques.

A High-Sensitivity Superconducting Detector

Weakly connected superconductors can function as very low power sensors by utilizing the coherence properties of superconductors. One configuration which has produced significant success incorporates a superconducting point contact and a small resistance element in a low-inductance superconducting circuit. When the critical supercurrent (ic) of the point contact is of the order of φ0/L, (φ0=h/2e, L=inductance of the ring), that circuit exhibits coherent quantum behavior. Used as a parametric amplifier, it has been used to measure ultralow voltages, limited by the thermal noise fluctuations in the resistance element R. The voltage sensitivity is approximated by 8kTR/φ0, where k is Boltzmann's constant and T the absolute temperature of the resistance R. We have measured 4×10−16 V across 1.7×10−10 Ω at 4.2°K with a signal-to-noise ratio approaching 10. The operation of this sensor follows from the Josephson oscillation of voltage-biased superconducting point contacts. A dc voltage V0 across the resistance of the circuit produces an oscillating current at the angular frequency ωJ=2πV0/φ0 and an oscillating voltage across the point contact at ωJ. Upon supplying an rf or microwave current at frequency ωD, the point contact mixes ωJ and ωD. Using a homodyne detector at ωD of bandwidth larger than ωJ, we can retrieve the oscillation at ωJ. Direct measurement of this frequency ωJ yields V0. Such superconducting circuits may be useful as cryogenic thermometers, as thermal radiation sensors, and in low-level spectroscopy.

Microplasma Breakdown in Germanium

Interpretation of breakdown results in Ge diodes is frequently complicated by effects associated with surface excess current. When these effects are minimized, breakdown is observed within the junction at a ``breakdown center,'' starting at a definite voltage VB, and is accompanied by the onset of microplasma pulses. In any one diode, there may be a number of centers, each having its characteristic value of VB and producing characteristic microplasma pulses. The minimum value of VB determines the breakdown voltage of the diode and it is possible to increase the latter radically by etching away centers having lower values of VB. Observations were made at temperatures from −253° to 27°C on Ge alloy junctions (n-type base resistivities from 0.54 to 5.4 Ω-cm). The properties of the pulses are discussed in some detail: the effect of raising the voltage above VB, the effect of light, and the temperature coefficient of VB. Values of the last are sufficiently high to suggest that suitable diodes can be used as cryogenic thermometers capable of reading smaller changes than 0.01°C at −253°C. Various aspects of the microplasma breakdown are discussed: the mechanism for triggering a pulse and that for ``turning it off,'' the role of the spreading resistance, the possible role of a negative resistance at breakdown, and the effect of microplasma breakdown on the measurement of carrier multiplication at voltages in the vicinity of breakdown.

GaAs junction diodes as cryogenic thermometers

It has been observed that the forward voltage drop, at constant forward current, of a GaAs diffused p-n junction varies almost linearly with temperature from 2.0° K to above 300° K. Since carrier freeze out, at low temperatures is not observed, these junctions make excellent cryogenic thermometers. In addition these diodes exhibit good repeatability on temperature cycling and an insensitivity to magnetic fields. The sensitivity of the devices measured near room temperature is Δ/VΔT∼ -3.5 mv/°C; I f = 0.1 µA Δ/VΔT = - 2.0 mv/°C; I f = 1.0 µA The sensitivity decreases slowly toward lower temperatures and at liquid Helium is: ΔVΔT∼ - 1.5 mv/°C and is essentially independent of current. This high sensitivity over such a wide temperature range is unique among cryogenic temperature indicators.