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The long-term stability of well-known TVO sensors before and after gamma irradiation was investigated during almost 17 years. Five of six sensors, calibrated in the temperature range from 3 to 300 K, were selected according to a requirement of their relative accuracy ΔT/T ≤ ± 0.25% at the cryogenic temperature range. Long-term stability measurements made 7.5 years after calibration are in good agreement with this value at 293, 77.3, and 4.2 K. Then these sensors and the sixth sensor, taken as the “worst” one for comparison, were irradiated by the 60Co gamma source at room temperature up to the total dose of about 1 MGy. Noticeable relative temperature shifts (more than ± 0.25%) are revealed for all the sensors after irradiation, and this fact is explained based on the model of structural changes in the volume of the sensitive element. Post-irradiation measurements carried out during 9 years at 293, 77.3, and 4.2 K indicate good stability of the sensors after irradiation.

The operation of a gamma densitometer (GD) of ID = 100 mm is considered; it is intended for the diagnostics of three-phase oil–water–gas flows using the separationless method, when the composition of components is determined by a spectrometric analysis of gamma irradiation with two different photon energies. The 241Am and 137Cs isotopes, installed in the same housing, are used as gamma sources, while a gamma detector is made on the basis of the BGO crystal of 40 mm in diameter and height. Information about the design, measuring electronics, and main characteristics of the GD is given. The method used for the temperature stabilization of the recorded radiation intensities for both isotopes within a range of ambient temperature from 10 to 35oC is presented.

Credible data on the actual characteristics of thin-film platinum temperature sensors with a nominal value of 1000 Ω in a wide temperature range of 3.8–370 K derived from long-term experimental studies of a large batch of 130 sensors are presented (most likely, for the first time). These characteristics are the temperature dependence of resistance, sensitivity, short-term and long-term stability, response to thermal cycling in the 293–77.3 K range, thermal resistance in liquid nitrogen and helium, measurement accuracy and interpolation polynomials, and gamma-radiation resistance. The calibration data are compared to the DIN EN 60751 standard and equivalent information for a pure platinum sensor. It is demonstrated that the actual parameters of sensors of the studied type are better than the datasheet ones: contrary to literature data, the measurement accuracy at cryogenic temperatures improves as the temperature decreases. Ways to increase the accuracy rating of these sensors are discussed. Data on their practical application in the XFEL superconducting accelerator project (Hamburg) and other projects are also provided.

The characteristics of two kinds/types of well-known TVO sensors are compared. They differ, probably, with respect to the quality of initial components and the shade of their green ceramic coating. Detailed information about long-term stability of the first kind of sensors are presented 10 years after calibration for a fairly large group of 52 pieces at room temperature, in liquid nitrogen and liquid helium, at atmospheric pressure and at Ts ≈ 1.9 K. Another group of 31pieces similar sensors was tested 15 years after calibration at room temperature, in liquid nitrogen and in liquid helium at atmospheric pressure. These sensors are based on TVO resistors produced previously, in the year 1991. Sixty pieces of the second kind of TVO resistors produced in 2009 were thermo-cycled between room temperature and 77.3 K, and two groups of 7 and 9 pieces were selected for test on their stability during 2.5 years at room temperature, in liquid nitrogen and in liquid helium at atmospheric pressure. A comparison shows noticeably better performances for the first kind of TVO resistors of dark green color. In particular, their sensitivity is roughly twice as high at liquid helium temperature. Information regarding the stability of well-known Cernox Cx-1030 sensors 9 years after calibration is also presented for comparison.

This paper is a review of our works on implementation of measuring systems for two-phase helium, hydrogen, liquefied natural gas (LNG) and oil production. In principle, two-phase flow-meters combining void fraction radio-frequency (RF) sensors and narrowing devices are considered in details. In particular, they can be applied for superconducting accelerators cooled with two-phase helium, refueling hydrogen system for space ships and some applications in LNG production industry. To produce these cryogenic two-phase flow-meters it is necessary to combine such devices as low temperature sensors, cryogenic void fraction sensors, sensors responsive to average velocity of the two-phase flow, pressure sensors and electronics to measure their signals. The measuring systems for two-phase liquefied natural gas (LNG), and oil-formation/salty water flows are also presented. These systems are based on combination of a gamma-densitometer and a narrowing device. It is shown as well that the experience gained allows separationless flow-meter for three-phase oil-gas- formation water flows to be produced.

This paper is a review on implementation of measuring systems for two-phase helium, hydrogen, liquefied natural gas (LNG), and oil-formation/salty water flows. Two types of such systems are presented. The first type is based on two-phase flow-meters combining void fraction radio-frequency (RF) sensors and narrowing devices. They can be applied for superconducting accelerators cooled with two-phase helium, refueling hydrogen system for space ships and some applications in oil production industry. The second one is based on combination of a gamma-densitometer and a narrowing device. These systems can be used to monitor large two-phase LNG and oil-formation water flows. An electronics system based on a modular industrial computer is described as well. The metrological characteristics for different flow-meters are presented and the obtained results are discussed. It is also shown that the experience gained allows separationless flow-meter for three-phase oil-gas-formation water flows to be produced.

A new version of a system to monitor the average void fraction, φ, the quality, x, and the mass flow rate, G, of two-phase liquefied natural gas (LNG) flows is offered. It is based on a combination of a gamma-densitometer with a Cs-137 radioactive source and a narrowing device. The metrological characteristics of this system are estimated and its practical realization is substantiated. A model of ID =100 mm has been manufactured and tested at the State Primary Special Standard of the Unit of Mass Flow Rate of Gas-Liquid Mixtures GET 195-2011 (Kazan, Russia) with simulated two-phase flows “Exxsol – compressed air”. The offered system can be used for pipelines up to ID =500 mm by applying a gamma source with the necessary activity. The experiments on GET 195–2011 have shown that the void fraction error and the relative mass flow rate error for Exxsol do not exceed 5% and 2%, respectively, at φ

The calibration principle of the cryogenic void fraction RF-sensors of a round cross-section for a wide temperature range is proposed and described in detail. It is shown that the simplest and reliable method of the calibration procedure requires finding a dependence of the resonant frequency, f, of the empty sensor on its temperature and only two f-values when it is filled with saturated liquid and vapor at the given temperature T0. The calibration test-bench is described. The errors of the calibration are estimated, and the experimental data for helium, hydrogen and nitrogen are presented.

Thе report concerns resistive temperature sensors, their calibration system and features to mount these sensors; RF-void fraction sensors and set-up to calibrate them; a discrete level-meter based on a resistive temperature sensor; and two-phase helium flow-meters. A way to produce a multi-channel measuring system is proposed to be applied for superconducting accelerators like FAIR-SIS100 and NICA. It is also shown that the experience obtained in cryo-diagnostics allows one to produce the separation less flow-meters for the three-phase oil-salty water-gas flows which are typical in the oil production industry.

The design and operating principle of a two-phase flowmeter for mixtures of oil and stratal water based on a restriction and gamma densitometer are presented. Results of tests of the flowmeter on the Multiphase Test Facility of TUV SUD NEL Ltd (Glasgow, Great Britain) are presented. The operating features of the restriction are noted and the compliance of the obtained characteristics of the flowmeter with State Standard requirements is evaluated.

On the basis of experimental data, operation of the conical narrowing device, which is a part of the separationless three-phase flow-meter “oil-water-gas” of ID = 100 mm, is analyzed. The component composition is determined by a spectrometric dual energy gamma densitometer in this flow-meter. With the involvement of the study of model horizontal single-phase, two-phase and three-phase flows, operation features of the narrowing device are revealed and an approach to the assessment of the main parameters of the flow meter is justified. Experimental data were obtained for more than 500 combinations of component compositions of single-phase, two-phase and three-phase flows. Most of the obtained relative errors in determining the flow rates of liquid components are within the limits recommended with Russian State Standard − GOST R 8.615-2005.

A promised continuation of the previous paper by concerning determination of the volume fraction of water and the total volume flow rate of the salty water-in-oil two-phase flow is presented. The measuring system consists of an RF-sensor and a narrowing device. The RF-sensor responds to complex permittivity of the flow, whereas the pressure drop along the narrowing device depends on the flow rate. The results of the tests presented earlier were not perfect because the temperature effects had not been considered. In this paper an improved variant of the algorithm for the same measuring system and the same flows is offered. This algorithm takes into account the temperature dependence of physical properties of the flow as well as own temperature dependence of RF-sensor characteristics. Comparison of the errors of the previous and new algorithms is carried out. The improved algorithm makes the measuring system applicable under real conditions.

A new variant of the void fraction RF-sensor of the round cross-section with ID = 38 mm is presented. Its sensitive part is made of the ceramic pipe with a meander line on the outer surface. This technique does not disturb the flow moving in the metal pipe of the same diameter. The technical solutions to provide rather high uniformity of the electric field within the sensitive volume and excellent stability of the readings are described. Irregular steps of the meander line are chosen after computer calculations and experimental checking. Some disadvantages of the previous modifications are shown as well. A new calibration procedure is discussed: it takes into account the dependence of the resonant frequency of the empty RF-sensor on the temperature of the sensor body. The method to find a mass flow rate of the two-phase helium and hydrogen flows in the range of void fractions from 0% to 100% is demonstrated with the new RF-sensor.

This paper concerns the features of a measuring device as well as two semitheoretical algorithms to find values of water cut, w, and flow rate, Q, for inverse emulsion flow “salty water-in-oil”. The measuring device is based on a combination of an RF-sensor, responding to complex dielectric permittivity of the flow, and a narrowing device. It is an upgraded variant of a diagnostics system to find characteristics of two-phase cryogenic flows that have been described by us earlier. The semitheoretical algorithm to find w- and Q-values is a paramount constituent element of the considered system. It takes into account hydrodynamic and electrodynamic features of the water–oil flow, the main of them are high viscosity value and conductivity of the salty water. Tests of the discussed measuring system with flows contained real crude oil and different kinds of water, including formation/stratum water, are described. A comparison of the experimental results and calculations based on the developed semitheoretical algorithms, are demonstrated and discussed. This comparison has allowed errors of the described algorithms to be estimated.

While operating with multicomponent flows, one needs to determine such characteristics as temperature, pressure, mass flow rate and component composition – mass quality, and void fraction. The main attention is given to measurement of mass flow rate of the two-phase cryogenic flows which can be used for superconducting accelerators, refueling hydrogen system for space and liquid natural gas industry, in particular. On the one hand, a two-phase flow is one of the simplest cases of multi-component flows which can be observed in cryogenics. On the other hand, this is rather sophisticated problem in cryogenics to create two-phase flow meters and estimate their metrological characteristics. This problem is discussed. Two methods are suggested – calorimetric and pressure drop ones. Features of the calorimetric method are discussed in this part.

An empirical method is presented to calculate magneto-resistance (MR) and a corresponding temperature shift of the well known TVO temperature sensors in the ranges from 0.1 K to approximately 10 K and up to 8 T. Features of MR, depending on the temperature and magnetic field, are discussed. The maximum positive MR-values, depending on the magnetic field, correspond to the temperature of T ≈ 0.67 K: 12.5% at 8 T. At the fixed magnetic field the zero MR-value is reached both by increasing or decreasing the temperatures with respect to 0.67 K. For example, at the magnetic field of 4 T, the zero MR-value appears at T ≈ 0.2 K and T ≈ 6 K. A constant moderate negative relative MR of 19%, which does not depend on the magnetic field from 2 to 8 T, is revealed at T ≈ 0.1 K. In the ranges from 1.5 to 4.4 K and from 0 to 9 T, in particular, the temperature shift has a linear dependence on B -value and inverse proportionality on the dimensionless sensitivity S . A brief explanation of the behavior of TVO sensors under magnetic fields is presented as well.

The report continues our investigations on cryogenic thermometers. To estimate the influence of warming the well known TVO temperature sensors [Proceedings of the ICEC17 (1998) 699, Cryogenics 41 (2001) 213, Advances in Cryogenic Engineering 45B (2000) 1817, Proceedings of the ICEC18 (2000) 627] up to 425 K on their calibration curve, a series of experiments have been carried out. The number of thermal cycles in the range from 425 K down to 77.3 K was 105. Comparison of readings of the sensors at 293, 77.3 and 4.2 K was performed with initial calibration curves for 100 cycles. Then several sensors were re-calibrated, and a new comparison was done during five additional thermal cycles at the same temperatures. The obtained results are discussed and they seem to be optimistic.

Information about tests of arbitrary chosen 20 TVO resistive temperature sensors in the range from 1.5 to 5 K under magnetic fields up to 9 T is presented. Based on the obtained experimental data – more than 2000 points, the approximate and accurate methods to calculate the magneto-resistance and corresponding temperature shift due to the magnetic field are reported as well. As shown, TVO is a sensor with predictable characteristics within the investigated ranges.

The designed, manufactured and certified devices and metrological systems to control the thermodynamic state of two- and single-phase cryogens are presented. These systems and the developed methodology provide an accuracy of calibration not more than ±5 mK for resistive temperature sensors in the range from 1.5 to 300 K and ±1.5% or less for radio frequency void fraction sensors intended for helium, hydrogen, nitrogen and others. The thermodynamic diagram temperature–dielectric permittivity for helium is presented as well.

This paper reports the specific features of the radio frequency method used to measure characteristics of cryogenic flows. The techniques for determination of the void fraction and quality of two-phase flows and the mean integral thermodynamic characteristics of single-phase flows, e.g. temperature and density, are described. The design and basic parameters of sensors with channels of round and annular cross-section are discussed. Possible combinations of these sensors with other devices for the measurement of two-phase and single-phase medium flow rates are shown. Information about the measuring system as well as measurement results for helium and nitrogen are presented. The sensor characteristics for hydrogen and methane have been estimated theoretically.

This paper reports the investigation of the structure of two-phase helium flows used for cryostatically controlling superconducting magnets in installations such as HERA, NET, UNK and KEK. Flow pattern maps for horizontal round channels and rectangular slot channels are plotted on the basis of experimental data obtained for a wide range of flow parameter variations. Some typical features of the flows (e.g. the absence of a slug pattern) are pointed out and attempts are made to explain these features following a theoretical analysis. Methods for estimating stratification and full mix limits are proposed. The position of the limits on the maps obtained for helium is shown to be quite different from that of other two-phase mixtures.

Large quantity of cryogenic temperature sensors will be used for operation of the International Linear Collider (ILC). Most of them will be subject to high radiation doses during the accelerator lifetime. Understanding of particle energy spectra, accumulated radiation dose in thermometers and its impact on performance are vital in establishing technical specification of cryogenic thermometry for the ILC. Realistic MARS15 computer simulations were performed to understand the ILC radiation environment. Simulation results were used to establish radiation dose requirements for commercially available cryogenic thermometers. Two types of thermometers, Cernox® and TVO, were calibrated prior to irradiation using different technique. The sensors were subjected then to up to 200 kGy electron beam irradiation with kinetic energy of 5 MeV, a representative of the situation at the ILC operation. A post-irradiation behavior of the sensors was studied. The paper describes the MARS15 model, simulation results, cryogenic ...

It is established as a result of an experimental investigation that the quantitative and qualitative characteristics of nonstationary heat transfer depend substantially on the two-phase helium flux structure. A simple working model that permits estimation of the influence of the expended mass vapor-content and density of the heat flux on the dynamics of the process for a homogenized phase distribution (bubble and emulsion flow modes) is proposed to describe nonstationary film boiling. The fundamental heat transfer singularities under conditions of a dispersely annular flux structure are noted.

Publisher Summary This chapter presents a temperature monitor to measure cryogenic temperatures by means of resistive temperature sensors. This is a box of 172 × 76 × 24 mm3 connected to COM-port (RS232) of a personal computer. A four-lead technique is used to measure the resistance of the temperature sensor with respect to the precision reference resistor. The main characteristics are: the number of measured channels/sensors can be from 1 up to 15 or 16; the range of measuring direct current is from 0.5 μA to 5 mA; the range of measured resistances, R, is from 1 Ohm to 100 kOhm; the accuracy of measurements is ∆R/R

The report continues our investigations of the thermometers which can be operated under conditions combining high radiation environment and cryogenic temperatures. To clarify temperature shifts due to fast neutron irradiation up to 10 16 n/cm 2 , additional platinum, carbon-glass and TVO temperature sensors were tested. The selected sensors were preliminary calibrated, and a series of experiments were carried out with irradiation of the sensors at 77.3 K and 293 K when their readings were measured in-situ. The post-radiation behavior of the sensors was estimated as well. The obtained results are discussed.

This work continues the activity to determine the thermodynamic state of both vapor-liquid and single phase cryogens taking into account the pressure or temperature and dielectric permittivity e. To find the value of e depending on void fraction, φ, one can use the radio frequency (RF) method when an investigated medium fills a volume whose resonant frequency is a function of e(φ). It is clear that a reading of the sensor depends on the 8-values of both the phases and flow pattern as well. The technique enabling to measure void fraction of the flow in vertical channels was presented at ICEC17. The sensor with a uniform electric field with the constant direction within the measuring volume was used in that case. This paper presents a new version of the RF sensor with a round cross-section for asymmetrical flows which can be observed in horizontal channels. The key feature of the sensor is that its sensitive part is fabricated by means of a twisted meander line formed on a dielectric tube, and this sensor can be used to determine an integral φ-characteristic of the flow. The feature of the RF measuring system is the use of a method based on a sweep generator and subsequent detecting the signal of the sensor, its digital transformation and mathematical processing. Such an approach allows one to provide a relatively small error of the measurement even at room temperature when RF-quality of the sensor is relatively low. The operation characteristics and test results for the developed sensor and measuring device are reported.

Four types of commercially available cryogenic thermometers were irradiated by gamma and/or neutron sources. These sensors are the well known rhodium-iron and platinum resistance thermometers, carbon resistance thermometer of TVO type and thin-film germanium resistance sensors; they can operate over the 1.5 K to 350 K range (14 K — for platinum sensor). The radiation source for experiments is the Fast Pulsed Reactor of Frank Laboratory for Neutron Physics, JINR. The total doses were about 1016 n/cm2 and 105 Gy at average energy of the fast neutrons of 1 MeV. The thermometers were calibrated at cryogenic temperatures and irradiated at 290 K, after that the comparison of the new calibration to the old one was made. Then the thermometers were irradiated and calibrated in-situ at 77.4 K. In addition, several tests of the thin-film germanium, platinum and TVO-carbon sensors were performed in the magnetic field. The obtained results are discussed.

The report presents the technique, calculation results and diagrams which allow to determine the interrelations between such parameters of cryogenic action as the time period, rate of cooling of the frozen phase, the relation between the depth of proposed necrosis and the depth of the frozen tissue, and the size of the cryoprobe and its surface temperature. The results of simulation are in good agreement with the data obtained during cryotherapy applications carried out at a zoological clinic.

A magnetoresistance (MR) of the well known TVO resistor temperature sensors has been studied at ultralow temperatures from approximately 0.8 K down to approximately 0.1 K under strong magnetic fields up to 8 T. A crossover from positive to negative MR with lowering temperature is found at weak magnetic fields. A zero MR-value at the magnetic field of 4 T, for example, is reached at T approximately 0.2 K. At sufficiently strong magnetic field the negative MR is suppressed and MR returns to positive values. A constant negative MR, which does not depend on the magnetic field from 2 to 8 T, is revealed at the lowest temperature T approximately 0.1 K. The observed behavior of the TVO sensor is explained basing on the model of hopping conduction via localized states in the weak localization regime.

Presented here are the results of the experimental study of transient thermal processes taking place in response to a heat disturbance at the interface of “solid - liquid helium”. A feature of the experiment performance is that the thermal power generated in a heater is strictly controlled in time in accordance with a preset rule. The data we report are for a heat load input as a single trapezoidal pulse. The results demonstrate a significant effect of the power pulse leading edge time on the heat transfer dynamics. Established here is a universal character of the map of transient heat transfer modes. A method is proposed which allows for accurate determination of transient characteristics, pattern boundaries, e.g. crisis moment and boiling-up point.

The paper presents the methods of optimizing the transducers designed for measurements of the void fraction of two-phase flows in the channels of round and annular cross section. On the basis of the analysis performed concrete solution of relatively high technical characteristics is proposed. Rated and actual characteristics of signal ranges and measurement errors are given for both sensors. Influence of the mass velocity on the void fraction of adiabatic two-phase flows is theoretically analysed. Effects of friction and of liquid-into-vapour entrainment are shown. Calculation results are compared with the obtained experimental data for helium. Special attention is given to the specific features of the processes in channels with different cross section.

This article presents results of investigations of the cryogenic thermometers which can operate under high radiation environment. To clarify the temperature shifts due to gamma irradiation up to 1 MGy, the platinum (two types), carbon-glass, and TVO temperature sensors have been tested. Before the irradiation run, the selected sensors were calibrated and a series of experiments was carried out under irradiation of the sensors at 77.3 and 293 K when their readings were taken in situ. Afterwards, the postirradiation evolution (short and long time) of the sensors was measured at 4.2, 77.3, and 293 K. The results, depending on the type of the sensor, can be optimistic or pessimistic. Some comparisons with analogous data for fast neutron treatment have also been made.

1. The principal factors to be controlled in the freezing of tissues are the depth of necrosis Ln, the depth of freezing Lf, the rate of cooling VT, and the time τn required for the cold to operate. Operation is considerably improved when temperature of the instrument Tc is reduced to that of liquid neon. Operating conditions are greatly affected by the relationship between the quantity Ln and characteristics of the freezing instrument, for example the radius r0 of the tip.

Experimental data is presented on the pressure drop in the motion of a two-phase helium flow in a horizontal pipe under adiabatic conditions and with a supply of heat.

Criteria are obtained for the ambiguity of HDC of boiling channels which allow for local inlet and outlet drag. Results of calculations presented for the most commonly used cryogens indicate the possible ambiguity of the HDC.

Results are presented from an experimental study of heat transfer from a cylindrical specimen to a volume of superfluid helium with thermal loading in the form of an impulsive step. Unique features of He II as a cooling agent as compared to He I are noted and discussed.

A method is described for simulating tissue temperature in cryosurgery by numerical solution of a heat-conduction problem with a mobile phase interface. The results are compared with experiment.

Transient thermal processes at solid-Hell interface under step pulse heat load input are brought into exploration. Particular attention is given to the influence of geometry of experimental specimen upon the heat transfer dynamics. Dramatic breakdown of fine heat transfer modes caused by development of superfluid turbulence under confined conditions is revealed, and accompanying temperature excursions are traced. Certain character parameters are selected, their dependences on experimental conditions being established.

Two-phase helium flows experimental and theoretical exploration results, including data on flow regimes, pressure drop, and void fraction, are presented. The circular, annular, and slot channels are examined. All the considered data are for low mass velocities and near-adiabatic conditions.