A Sweeping Pulsed Radar–Reflectometer for Measuring the Electron Concentration Profile of Plasma

An instrument for measuring the electron concentration profile in magnetic confinement plasma devices is described. The instrument combines the advantages of rapidly tuned (sweeping) phase reflectometers and multichannel time-of-flight pulsed reflectometers and ensures measurements of the electron concentration profile at electron densities of 4.7 × 10¹²–4.5 × 10¹³ cm^–3 for 16 s.     

A Torsion Balance for Studying Anisotropic Magnetic Properties of Superconducting Materials

A low-temperature torsion balance for studying magnetic properties of superconductors is described. The device can operate in the modes of the rotation or vibration of an axisymmetric superconducting sample in an external magnetic field. The balance provides for the measurement of a torque of 10^–8 –1 N·m applied to the sample. The device is highly sensitive to frozen magnetic fluxes even of the order of magnitude of the geomagnetic field (H 0.5 Oe). To eliminate the effect of frozen magnetic fluxes, two-layer Permalloy shields providing for the cooling of the sample in the field H < 10^–3 Oe are used. The capabilities of the developed method for studying critical parameters and the anisotropic magnetic properties of superconductors are described.     

A Channel for Neutron Flux Measurement

The design principles of a channel for measuring fluxes of thermal neutrons in a nuclear-reactor control and protection system are considered. The channel consists of a fission chamber, a set of boron-containing gas-filled ionization chambers, and an electronic unit that ensures a counting rate of fission pulses of up to 1 × 10⁶ s^–1. It is shown that the widest linear range is achieved in channels equipped with a fission chamber and a gas-filled ionization chamber with electrodes coated with natural boron. The channel allows for measurements of the thermal-neutron flux density in a range of 0.5 to 5 × 10¹¹ cm^–2 s^–1.     

An Automated Installation for Measuring the Complex Thermal Expansion Coefficient of Polymers by the Modulation Dilatometry Technique

An installation designed for measuring the relaxation component of thermal expansion, a typical feature of polymers due to the conformational mechanism of thermal expansion inherent in them, is described. The relaxation component manifests itself as a shift in the expansion variation phase relative to the temperature variations. The installation allows variations of the temperature-oscillation frequency and amplitude in the ranges of 10^–3 to 10^–1 Hz and 1–5 K, respectively. The expansion variation amplitudes were measured using a mechanotron with a sensitivity of at least 10^–2 m. The serviceability of the installation was demonstrated in studies of the thermal expansion of a polymer (polyvinylacetate, PVA). In these studies, a shift in the expansion–temperature phase in the polymer-vitrification region and its dependence on the temperature-oscillation frequency were recorded.     

A Programmable Device for Experiments Employing a Superheated Probe in the Pulsed Operation Mode

A device was developed for experiments on the controlled heating of a thin wire probe immersed in the substance being analyzed, with penetration into the region of short-lived (superheated) states of the substance. The thermostabilization of the probe, pulse-heated to the selected temperature T _pl(t > t _pl), is described. Using the iteration method, the software fits the coefficients of the heating function to reproduce the required temperature regime with an error of <0.5% over 10–20 cycles. The length of the stabilization pulse in the experiments was 1–10 ms at probe temperatures as high as 1000 K. The sensitivity of the compensation technique of relative measurements to relative changes in the thermophysical properties of a superheated substance was 10^–3 at a characteristic time of 10 s.     

A Hall Microscope for Visualizing the Magnetic States of Objects

A three-dimensional microscope with a sensitivity of 2.5 G/Hz^1/2 has been developed on the basis of two Hall probes. The magnetic field dynamic range of the microscope at a frequency of 19 Hz is 2.5 G–80 kG. The maximum observed area of the objects under study is 7.5 × 7.5 mm² with a resolution of 50 × 50 m². The minimum scanning step along the X and Y axes is 5 m. The maximum displacement along the Z axis is 25 mm with a minimum scanning step of 1 m. An arbitrarily shaped instrument function can be created in the magnetic complex by combining the temperature, the stationary and alternating magnetic fields, and the transport current. The microscope was used for the spatial and temporal visualization of the structure and properties of the critical state, as well as for diagnosing superconductors at temperatures of 4.2–300 K in magnetic fields of 0–80 kG.     

A Triggered Gas-Filled Metal–Ceramic Spark Gap with a High Current Rise Rate and Stable Operation

A triggered gas-filled three-electrode metal–ceramic -01 spark gap with a field distortion is described. This device is intended for use as a nanosecond switch. Spark gaps operating within voltage ranges of 15–30 and 30–60 kV have been developed, manufactured, and tested. The operation delay with respect to the trigger pulse is 60 × 10 ns. Life tests at a pulse repetition rate of 1.1 Hz have shown that the parameters of spark gaps do not deteriorate after the total number of operations of up to 3 × 10⁶, which corresponds to a total charge of 4.5 × 10⁴ C. The probability of a breakdown during life tests was 10^–4. A batch of 20 spark gaps has been manufactured for the operation in a pulse voltage generator for supplying the discharge in a large-volume pulsed CO₂ laser. The test results confirm the stability of the parameters of the devices in the batch.     

An Extension of the Conductance-to-Electrical Signal Conversion Range of Capacitance Transducers by Using Self-Excited Oscillators with a Thermistor Bridge

A circuit for the compensation of unbalance is proposed, which allows one to decrease essentially the temperature stability effect on the error and conductance conversion range of a capacitance transducer in self-excited oscillators with a thermistor bridge. The device that converts simultaneously and independently the conductance of the transducer in a range of 10^–6–5 × 10^–3 S with an error of 5% and capacitance in a range of 10^–2–100 pF with an error of 1% into an electric signal is described.     

A LIRA Twin-Wave Laser Interferometer–Reflector for Plasma Diagnostics at Large-Scale Facilities

A LIRA interferometric system (active laser interferometer–reflector) is designed for measuring the plasma density and controlling the degree of modification of the reflector surface under conditions of intense vibrations of a plasma facility. The operating principle of the system is based on the intralaser (autodyne) reception of the radiation reflected into the laser. An element of the structure of the laser facility, including a diffusely reflecting surface, can be used as a reflector. The interferometer is built on the basis of two Zeeman He–Ne lasers generating at wavelengths of 632.8 and 3392.2 nm. Under conditions of an actual plasma experiment, a sensitivity of 5 × 10^–7 has been achieved, which, when converted into the linear plasma electron density, is n _e L = 2.5 × 10¹⁰ cm^–2. The highest time resolution is 10 ns. The interferometer can operate using reflectors with a coefficient of power reflection into the laser of up to 1 × 10^–12.     

A Magnetometer Based on a Hall-Effect Transducer

An induction meter based on a Hall-effect transducer with in-phase signal suppression and thermostabilization circuits is described. It is powered by a 10³-Hz ac line. The maximum relative error in temperature measurements from 0 to 70°C does not exceed 0.7 % for magnetic fields of 50–100 T, 0.4% for 0.1–1 mT, and 0.1% for 1–625 mT. In the range of 50–500 T, the error is determined by an in-phase signal. The contribution of the total temperature error is 0.01% per 50°C. Depending on the induction of the measured magnetic field, the resolution changes from 0.12 to 19 T.     

The Wave Complex of the СПРУТ-VI Instrument Package

The wave complex of the -VI instrument package was designed for monitoring the electromagnetic state around orbital stations. The method of combined wave probes enables simultaneous vector measurements of magnetic field fluctuations (in a frequency range from 0.1 Hz to 40 kHz) and the electric current density in plasma (in a range of 10^–6–10^–13 cm^–2), as well as determination of the station surface potential (in a range of 10^–3–20 V). The complex was used onboard the Mir station for investigating the fine structure of distributions of ionospheric charged particles at low and near-equatorial latitudes.     

High-Sensitivity Magnetometers Based on HTSC Ceramics

The magnetic response of the YBa₂Cu₃O_{7 – x} superconducting ceramics to an alternating magnetic field was studied experimentally. A magnetometer with a sensitivity level of 2 × 10^–7Oe was developed on the basis of the experimental data. The ways of improving such devices are discussed.     

A gas-ion source with a grid-stabilized plasma cathode

A two-stage source of a broad beam of gas ions is described. The source contains a grid-stabilized plasma cathode and an anode stage with a multicusp magnetic field. The emission current of the plasma cathode (which is based on a glow discharge with a hollow cathode) is controlled between 0.1 and 1 A. The voltage that is applied to a bipolar diode between its cathode grid and anode plasma and determines the energy of fast electrons ranges from 50 to 200 V. The operating pressure of the argon in the anode stage is 4 × 10^–3–1 × 10^–1 Pa. A beam of argon ions having an energy of up to 5 keV and a current of >100 mA is formed by a two-electrode ion-optical system with a working area of 50 cm².__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 107–111.Original Russian Text Copyright © 2005 by Gavrilov, Kamenetskikh.     

A Periodically Pulsed HF(DF) Gas-Discharge Laser

The design of a repetitively pulsed HF(DF) gas-discharge laser with an active-medium volume of 60 × 2.3 × 1.2 cm³, a pulse radiation energy of 1.6 (1.2) J, and a pulse repetition rate of 1–2 Hz is described. A zeolite-based absorber is used to stabilize the energy characteristics of the laser operating without the forced circulation of the laser mixture. An energy decrease by 50% after 10³ laser shots is obtained at a pulse repetition rate of 1 Hz.     

A new method for determining particle energy in the range 1011−1015 eV and results from a beam test at 180 GeV/c

A method for measuring the energy of the nuclear component of cosmic rays is described. The principle of the method consists in determining the energy of a primary nucleus from the space density of secondary particles produced in a thin target in the initial event of inelastic interaction. The results from testing the method on an ejected 180-GeV pion beam are presented. Analysis of the experimental data and simulation show that, using this method, it is possible to measure the particle energy with a relative error of 67%. The method is being developed for the direct detection of cosmic rays over wide ranges of energy (10¹¹–10¹⁵ eV/particle) and charge (Z = 1–30) during a cosmic experiment in near-Earth space.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 46–51.Original Russian Text Copyright ¢ 2004 by Bashindzhagyan, Voronin, Golubkov, Grebenyuk, Egorov, Kalinin, Karmanov, Konkov, Korotkova, Kozlov, Krumshtein, Merkin, Panasyuk, Pakhomov, Podorozhnyi, Postnikov, Roganova, Sadovskii, Sveshnikova, Sidorov, Tkachev, Turundaevskii.     

Setup for Stimulating and Measuring the Electrical Activity of an Olfactory Epithelium

A setup for recording the electrical activity of an insulated olfactory epithelium is described. The setup consists of the following basic elements: an electrophysiological chamber intended for supporting the vital activity of the olfactory epithelium, its isolation from outside smells, and stimulation by odor stimuli; a stimulation system intended for preparation of a saturated vapor of the stimulating substance, its dilution down to concentrations of 10^–4–5.6 × 10^–2 and application of air stimuli with a duration of 1–5 s and repetition period of 2–100 s; and a recording and control system, which is controlled manually or via a computer and synchronizes the stimulus application and olfactogram recording (K _amp = 10000, sensitivity is 10 V, bandwidth is 0–100 Hz) and automatic compensation of the transepithelial potential drift.     

Dry and oil-lubricated sliding wear of Si<Subscript>3</Subscript>N<Subscript>4</Subscript> and Si<Subscript>3</Subscript>N<Subscript>4</Subscript>/BN fibrous monoliths

A high-temperature ball-on-flat tribometer was used to investigate dry and oil-lubricated friction and wear of sintered Si₃N₄ and Si₃N₄/hexagonal boron nitride (H-BN) fibrous monoliths. The friction coefficients of base Si₃N₄ flats sliding against Si₃N₄ balls were in the range of 0.6–0.8 for dry and 0.03–0.15 for lubricated sliding, and the average wear rates of Si₃N₄ were 10^–5 mm³ N^–1 m^–1 for dry sliding and 10^–10–10^–8 mm³ N ^–1m^–1 for lubricated sliding. The friction coefficients of Si₃N₄ balls against composite fibrous monoliths were 0.7 for dry sliding and 0.01–0.08 for lubricated sliding. The average specific wear rates of the pairs were of the same order as those measured for the conventional Si₃N₄ pairs. However, the fibrous monoliths, in combination with sprayed dry boron nitride, resulted in reduction in the lubricated friction coefficients of the test pairs and significant reduction in their wear rates. The most striking result of this study was that the coefficients of friction of the Si₃N₄/H-BN fibrous monolith test pair were 70–80 lower than those of either roughened or polished Si₃N₄ when tests were performed under oil-lubricated sliding conditions over long distances (up to 5000 m). The results indicated that Si₃N₄/H-BN fibrous monoliths have good wear resistance and can be used to reduce friction under lubricated sliding conditions.     

Measurement of the Parameters of the Dielectric Windows of the Linear Collider TESLA Cavities

A setup for measuring the permittivity and the loss parameter of ceramic samples is described. The setup operation is based on a conventional method for measuring changes in the frequency and Q-factor values of cavities caused by insertion of experimental samples into the cavity. Cylindrical ceramic samples with the permittivity = 8–10 and loss parameter tan = (2–4) × 10^–4 were studied. A cylindrical E ₀₁₀ cavity with a cutoff waveguide attached to one of the faces of the cavity was selected, because it provided sufficient accuracy of measurement and could be effectively used for testing series of samples of various sizes and shapes at a fixed frequency of 1300 MHz. It was shown that the permittivity of various samples could be determined with an accuracy of 1.5%, whereas the loss parameter could be determined with an accuracy of 7%.     

Anomalous wear behavior of MoS2 films in moderate vacuum and dry nitrogen

440C steel thrust ball bearing races lubricated with 1 m thick sputtered films of MoS₂ were tested in the unidirectional and oscillatory modes against bare steel balls in moderate (10^–4–10^–5 Pa 10^–6–10^–7 Torr) vacuum and in 1 atmosphere of 99.999% pure ( 1 ppm water) N₂ in the same unbaked environmental chamber. Over 90% of the residual gases in the chamber vacuum consisted of H₂O vapor. The bearings operated in N₂ showed substantially longer lives compared to the specimens tested in vacuum. Scanning electron microscope (SEM) tribometry was also performed on an MoS₂ film powder-burnished onto a 440C flat. This flat was repeatedly oscillated against bare, hemispherical-tipped 440C pins on fresh wear tracks in the same type of N₂ and column vacuum of ~10^–3 Pa 10^–5 Torr itself containing over 90% residual H₂O. The SEM-generated results on the burnished film confirmed the same, atmosphere-dependent difference in wear life observed with the sputtered layers. Varying the moisture content of the burnished flat and its immediate environment by cryosorption predictably manipulated the coefficient of friction and wear life of MoS₂. The various possible causes of this perplexing phenomenon are reviewed, and a plausible hypothesis is offered attributing the unexpected wear life reduction to the physico-chemical consequences of residual H₂O hydrogen-bonding to the oxidized and/or hydrated edge and basal plane sites of MoS₂ in moderate vacuum. The site-specific sorption of water is severely hindered in 1 atm N₂ by the gas molecules disrupting the H-bonding mechanism.     

An AF-1 Analytical Fourier-Transform Spectrometer for a Wide Field of Applications

An AF-1 Fourier spectrometer is developed on the basis of a two-beam interferometer with a pendulum-type scanning unit, which is manufactured of a special alloy ensuring its time stability, and a stationary block of plane reflectors made of a highly stable glass. The performance characteristics of the instrument are as follows: the IR spectrum region is 400–4000 cm^–1; the highest resolution is 1 cm^–1; the accuracy of determining wave numbers is ±0.1 cm^–1; the optical-density measurement range is 0.05–3 units; the variations of the deviation from the 100% transmission level in the entire spectral region are within ±0.5%; the rms deviation of the optical density in the range of 0.2–2.0 units is 1%; and the signal-to-noise ratio in the range of 2000–2100 cm^–1 is at least 10⁴ for a measurement time of 2 min and a spectral resolution of 1 cm^–1.