A high-speed two-color pyrometer has been developed that allows measuring the intensity of thermal radiation in temperature range of 100-3500 o C with 2 μs time resolution. The analysis of the main factors affecting the measurement of surface temperature in the conditions of its interaction with plasma is carried out. It is shown that at plasma temperature of more than 10 eV and moderate concentration of particles, the wall plasma can be considered transparent to thermal radiation. Experimental studies on non-contact measurement of temperature of surface interacting with plasma on Globus-M2 tokamak and plasma gun test bench have been carried out. Sawtooth temperature fluctuations were detected on the wall of tokamak chamber near the exit of outer separatrix branch. The period of these flashes was 3-4 ms, and duration was 2 ms. The maximum wall temperature measured by a high-speed pyrometer exceeded the temperature measured by infrared camera. Measurements of temperature of the front surface of W-Li sample were carried out at plasma gun test bench under conditions of deuterium plasma jet cyclic action under loads simulating regimes of plasma current disruption in tokamak. The sample temperature reached more than 3000^oC during <1 ms. The thermal conductivity of the sample degraded with an increase in number of plasma exposure cycles, which was expressed in progressive decrease in target cooling rate after the pulse. Using a high-speed pyrometer, it is proposed to control the formation of heat-insulating foils on surface interacting with plasma Keywords: two-color pyrometer, thermal radiation, surface temperature, materials irradiation.

A high-speed two-color pyrometer has been developed that allows measuring the intensity of thermal radiation in temperature range of 100-3500 0C with 2 µs time resolution. The analysis of the main factors affecting the measurement of surface temperature in the conditions of its interaction with plasma is carried out. It is shown that at plasma temperature of more than 10 eV and moderate concentration of particles, the wall plasma can be considered transparent to thermal radiation. Experimental studies on non-contact measurement of temperature of surface interacting with plasma on Globus-M2 tokamak and plasma gun test bench have been carried out. Sawtooth temperature fluctuations were detected on the wall of tokamak chamber near the exit of outer separatrix branch. The period of these flashes was 3-4 ms, and duration was 2 ms. The maximum wall temperature measured by a high-speed pyrometer exceeded the temperature measured by infrared camera. Measurements of temperature of the front surface of W-Li sample were carried out at plasma gun test bench under conditions of deuterium plasma jet cyclic action under loads simulating regimes of plasma current disruption in tokamak. The sample temperature reached more than 3000 0C during < 1 ms. The thermal conductivity of the sample degraded with an increase in number of plasma exposure cycles, which was expressed in progressive decrease in target cooling rate after the pulse. Using a high-speed pyrometer, it is proposed to control the formation of heat-insulating foils on surface interacting with plasma.

Temperature response of a material to an external electric field is the main method for electrocaloric effect study in ferroelectrics. In this work, for 0.65PbFe2/3W1/3O3-0.35PbTiO3 solid solution as a model object, it is shown that with an increase in the electric field strength, current filamentation effect can occur. It leads to formation of local regions of increased conductivity in the sample. The associated thermal effect have short characteristic times, due to the small volume of the filament. They are comparable to the times of the electrocaloric response of the material, and can lead to significant errors in the detection of the electrocaloric effect. Keywords: electrocaloric effect, temperature response, ferroelectric ceramics, current filamentation effect.

Abstract A new approach to pyroelectric research based on the information-measuring theory of dynamical systems is presented and substantiated. The proposed technique is based on direct monitoring of both the sample temperature using a fast infrared sensor and pyroelectric current allowing precise quantification of the pyroelectric coefficient of bulk and film materials with high reliability and accuracy over a wide range of temperature and applied electric field. The capabilities of the method are demonstrated on AlN films, α-glycine crystals, and ferroelectrics.

Monolithic optical sensors based on low shunt resistance p-InAsSbP/n-InAs and p-InAsSbP/n-InAsSb heterostructures grown onto low-resistivity n-InAs substrates equipped with transimpedance amplifiers suffer from output electrical signal distortions. The paper presents analysis of the above distortions and an equivalent circuit for output electrical signal analysis and measurements, as well as recommendations for suppression of interference of signal components has been suggested. Keywords: optical sensors, ATR sensors, optopairs, p-InAsSbP/n-InAs(Sb) heterostructures

A new experimental approach to the complex study of electrocaloric, pyroelectric, and thermal effects associated with the bulk and local electrical conductivity of ferroelectrics and related materials is proposed. The key to this approach is the analysis of the dynamics of the sample temperature response to an arbitrary external action, including long-term electrical impacts. The metrological justification of the experimental technique is based on direct non-contact high-speed monitoring of the sample temperature using an IR photodiode sensor designed by Ioffe Institute. Its efficiency is confirmed by numerous experimental data on electrocaloric properties of ferroelectrics, relaxors, and relaxors-based multilayer structures.

Monolithic optical sensors based on low shunt resistance p-InAsSbP/n-InAs and p-InAsSbP/n-InAsSb heterostructures grown onto low resistivity n-InAs substrates equipped with trans-impedance amplifiers suffer from output electrical signal distortions. The paper presents analysis of the above distortions and equivalent circuit for output electrical signal analysis and measurements as well as recommendations for suppression of interference of signal components have been suggested.

Temperature response of a material to an external electric field is the main method for electrocaloric effect study in ferroelectrics. In this work, for 0.65 PbFe2/3W1/3O3 – 0.35 PbTiO3 solid solution as a model object, it is shown that with an increase in the electric field strength, current filamentation effect can occur. It leads to formation of local regions of increased conductivity in the sample. The associated thermal effect have short characteristic times, due to the small volume of the filament. They are comparable to the times of the electrocaloric response of the material, and can lead to significant errors in the detection of the electrocaloric effect.

A mid-infrared radiometric (MIR) method for precise in situ temperature measurements when studying pyroelectric and electrocaloric properties of bulk and film materials is presented. The method uses new MIR-temperature sensors based on narrowband high-speed and high-sensitive uncooled immersion lens A3B5 photodiodes with a precalibration procedure. They are completely insensitive to the background illumination with λ ≤ 1 µm and provide contactless temperature measurements directly in the area of laser heating action. An accuracy of 50 mK at the temperature around 20 °C, rapidly improving up to 1 mK at 200 °C, is achieved at the operation speed of 1 ms. The reliable and reproducible conditions of measurements of pyroelectric and electrocaloric properties of various samples are formulated, and the novel experimental setup is described in detail. The experimental verification of the method is performed by the measurements of pyroelectric properties of single crystals, bulk ceramics, and AlN film. The results of joint measurements of the pyroelectric and electrocaloric properties of the ferroelectric relaxor ceramics are also presented.

Detection of breakdown voltage and diagnostics of the pre-breakdown state of a material is a topical task of studying the characteristics of dielectric materials and structures on their base under applied external electric field. A new efficient method for diagnosing the pre-breakdown state of multilayer structures (MLC) based on the 0.55PbMg1/3Nb2/3O3-0.45PbSc1/2Nb1/2O3 (PMN-PSN) ferroelectric relaxor is considered. The method is based on the analysis of the dynamics of the MLC surface temperature changes upon application of an external electric field. A set of MLC samples was tested under the action of an electric field E = 10 - 120 kV/cm at temperatures from room temperature to 80 ℃. The critical electric field value characterizing the pre-breakdown state and, consequently, limiting the upper level of operating voltages for electrocaloric applications, was determined for PMN-PSN multilayer structures.

The determination of the breakdown voltage and the diagnostics of the prebreakdown state of a material is a topical problem of studying characteristics of insulating materials and structures based on them when applying an external electric field. The new effective method of the diagnostics of the prebreakdown state of multilayer structures (MLC) based on the ferroelectric–relaxor 0.55Pb–Mg1/3Nb2/3O3–0.45-PbSc1/2Nb1/2O3 (PMN–PSN) is considered. The method is based on an analysis of the dynamics of changing the MLC surface temperature during applying an external electric field. A series of the MLC samples has been tested under action of electric field E = 10–120 kV/cm and the ambient temperature from room temperature to 80°C. The critical electric field that characterizes the prebreakdown state of the PMN–PSN multilayer structures and, correspondingly, restricts the upper limit of operating voltages for the electrocaloric applications has been determined.

We have a new, effective method for direct measurements of the electrocaloric effect under arbitrary heat transfer conditions. The accuracy and reliability of measurements of the dynamics of changes in the sample temperature are due to the use of photodiode temperature sensors of the mid-IR range with the possibility of their in situ calibration.

A new effective method for direct electrocaloric measurements under arbitrary heat exchange conditions is proposed. The accuracy and reliability of the sample temperature measurements in dynamic provided by the use of mid-IR photodiode temperature sensors with the possibility of the in-situ calibration procedure

The electrocaloric effect and also the dielectric, pyroelectric, acoustic, and piezoelectric properties of a lead magnoniobate–scandoniobate solid solution in a biasing electric field have been studied. The dielectric and electromechanical contributions to the pyroelectric and electrocaloric effects are discussed.

Поступило в Редакцию 11 января 2018 г

We have studied the electrocaloric effect in 0.68BaTiO3–0.32SrTiO3 solid solution, as well as the dielectric, pyroelectric, and piezoelectric properties of this compound in the vicinity of the first-order phase transition in a bias electric field. The dielectric and electromechanical contributions to the pyroelectric and electrocaloric effects are discussed.

Efficiencies of optical pairs consisting of fast low-noise uncooled immersion LEDs and photodiodes based on InAsSb solid solution are studied. The proposed optical pairs are promising for applications in compact low-voltage sensors of carbon dioxide. The threshold sensitivity of such a sensor is several hundreds of ppm, and the measurement error is no worse than 5% in a wide range of concentrations (up to 10 v/v%) at a relatively high time resolution (50 ms) and a sample volume of no greater than 50 mL. Relatively high working rate and low volume of the sample improve diagnostics in capnography and allow applications in pediatrics and side-stream capnography including measurements of instantaneous CO2 concentration in the course of breathing.

AbstractThe electrocaloric effect and also the dielectric, pyroelectric, acoustic, and piezoelectric properties of a lead magnoniobate–scandoniobate solid solution in a biasing electric field have been studied. The dielectric and electromechanical contributions to the pyroelectric and electrocaloric effects are discussed.

AbstractWe have studied the electrocaloric effect in 0.68BaTiO_3–0.32SrTiO_3 solid solution, as well as the dielectric, pyroelectric, and piezoelectric properties of this compound in the vicinity of the first-order phase transition in a bias electric field. The dielectric and electromechanical contributions to the pyroelectric and electrocaloric effects are discussed.