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.     

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.     

Local High-Frequency Magnetron Reactive-Ionic Quartz Etching

A high-frequency magnetron reactive-ion etching system for the high-speed quartz glass surface treatment is described. The scanning assembly of the magnetron is located in a separate chamber pumped down to a pressure of 10^–2 Pa. This ensures a highly uniform etching and a high magnetic induction on samples, making it possible to reduce the cathode thickness. The quartz etching was studied in SF₆, CF₄, and CHF₃ with the magnetron operation with and without scanning. The maximum etching rates of 1.6 m/min (with scanning) and 4.2 m/min (without scanning) were attained in CHF₃ with a 1-Pa pressure and 700-W discharge power. 150-m-depth 4-mm-diameter pits were obtained by the quartz etching without scanning. With an increase in the pit depth from 150 to 250 m, the etching rate was reduced from 4.2 to 2.5 m/min.     

An Energy Source Based on Helical Explosion–Magnetic Generators for High-Impedance Loads

A transportable standard module developed at the Institute of Experimental Physics as a component of an energy source for modeling current pulses of positive lightning is described. The source is designed as a combination of several unified helical explosion–magnetic generators with output transformers and an inner diameter of the stator of 200 mm. According to our calculations, the source generates current pulses with an amplitude of up to 100 kA in loads with an inductance of 100 H and a resistance of several tens of ohms. The results from testing a typical module operating with a circuit having an inductance of 100 H and a resistance of 4 are presented. The experimental data coincide well with the results of a mathematical simulation of the module's operation.     

A Compact High-Voltage Power Supply for an Accelerating Installation

A compact high-voltage power supply for an accelerating installation that uses high-frequency (25 kHz) voltage conversion is described. The power supply provides a variable voltage of 5 to 100 kV at a load current of up to 250 A and three independently variable voltages of 0–100 V (100 mA), 0–2000 V (5 mA), and 1–15 kV (50 A), which are required for operating the cold-cathode ion source used in the installation. The output-voltage ripple is <0.05%. The power-supply efficiency is no less than 70%.     

A Simple Analog Input Unit for a Computer

A simple circuit of an analog digitizer, which inputs data into a computer with a voltage resolution of 10 binary bits and a time conversion of 150 s, is described. The unit can act as a plotter, digital measuring device, strobe-voltmeter, oscilloscope, etc. The unit does not contain expensive or complex components and operates with any computer equipped with a CENTRONICS-type printer port.     

A Study of Distortions in Double-Sided Emulsion Films by FoMos

FoMos makes double-sided emulsion tapes. Films of desired size cut from such tapes are used as emulsion trackers. The technique for measuring distortions is described, and the results of measurements are presented for several films cut from different sections of a standard piece of double-sided tape with a length of 7 m and a useable width of 20 cm. The standard plastic base of the tape under investigation is 190 m thick; 50-m-thick layers of diluted PX3 emulsion–gel are applied to its opposite sides.     

Microtribological Studies of Different Nanocomposite TiC/a-C:H Coatings Using a Modified Nanoindentation Setup

The microtribological behavior of different nanocomposite TiC/a-C:H coatings against 100Cr6 (AISI 52100) balls with 250 m radius has been studied using a modified nanoindentation setup and was compared to the results of macroscopic pin-on-disc (POD) experiments. First results reveal significant differences between macroscopic friction coefficients _POD determined using POD tests and microscopic friction coefficients _micro. On the macroscopic scale low friction coefficients can be obtained for high hardness coatings. On the microscopic scale the high hardness samples induce considerable wear on the steel counterbody leading to high microscopic friction coefficients of around 0.3. For samples with lower hardness no wear has been observed and low microscopic friction coefficients (< 0.2) can be acheieved.     

An Optical-Fiber Setup for Inert Particle Concentration Measurements

An optical-fiber setup employing laser light designed to measure concentrations of 50-to 500-m particles moving with a speed of up to 10 m/s is described. The time resolution, the measurement time, and the counting of pulses reflected from the particles are programmed. The setup has the following basic parameters: time resolution is 10 s, spatial resolution is 50 m, sample size is up to 32 × 10³, and particle counting error is within 1%. The setup was applied to measurement of the solid-phase concentration in a two-phase flow in a volum concentration range of up to 30%.     

A High-speed Charger of a Five-megavolt Shaper of Nanosecond Voltage Pulses

A generator of voltage pulses with an amplitude of up to 4.5 MV is described. The generator is a part of an oil-filled shaping line (in the following, called shaper) and enables a high-speed (in 0.5 s) charging of a coaxial line up to a voltage of 5 MV in order to decrease (by a factor of 2–3) the duration of the leading edge of the generated nanosecond voltage pulse. The circuit and design solutions that enable a very low specific self-inductance of the discharge circuit, 3.35 H/MV, are presented. The -4.5 generator has a rated voltage of 4.5 MV, discharge capacitance of 16 nF, stored energy of 162.0 kJ, self-inductance of 25.0 H, and a probability of no failure of 0.9987.     

Pulse Train Microprocessor Programmer for NMR Relaxometers-Diffusiometers

A pulse train programmer for a spin–echo NMR relaxometer–diffusiometer is based on an AT89C51-24PC microcontroller. The programmer ensures the arbitrary generation of pulse trains with a minimum train step of 30 s and recording of up to 30000 10-bit amplitudes of spin–echo NMR signals with a minimum quantization step of 3 s. The all-in-one one-board programmer is connected to a computer serial asynchronous data port, which is compatible with NMR relaxometer–diffusiometers of almost any design.     

A Magnetizer for Studying Transient Processes in Magnets over a Wide Time Interval

The magnetizer is intended for studies of transient processes in magnetic samples shaped as plates or planar films. The main element of the magnetizer is a strip line consisting of thin wires connected in series with damping resistors. The use of resistors makes it possible to reduce the eddy current decay time (and, therefore, the magnetic field settling time) to 5–6 ns and, in turn, to extend the range of durations of the processes under study and increase the spatial homogeneity of the field. The magnetization of samples is measured using a removable longitudinal sence loop. The magnetizer can be used to study a wide variety of transient processes with a duration of 0.05–100 s (in permalloy films, iron borate single crystals, garnet ferrite films with easy-plane anisotropy, etc.). The magnetizer can also be used to observe dynamic domains.     

Effect of the Concentration of Nd3+Ions in KGd(WO4)2: Nd3+Crystals on Laser Characteristics

Active KGd(WO₄)₂: Nd³⁺elements used in laser engineering have typical concentrations of Nd³⁺ions of 3 at. %. Our studies have shown that the optimal concentration is close to 4.5 at. %. This result is confirmed for active elements 3 mm in diameter and 50 mm long in two lasing modes at a wavelength of 1.067 m and in the stimulated Raman scattering (SRS) self-conversion mode at 1.538 m in a lamp-pumped laser.     

Frictional anisotropy of oriented carbon nanotube surfaces

This report examines highly anisotropic tribological behavior of multi-walled nanotube films oriented in mutually orthogonal directions. The average values of coefficient of friction varied from extremely high values (=0.795) for vertically aligned nanotubes grown on rigid substrates to very low values (=0.090) for nanotubes dispersed flat on the same substrates. The results were insensitive to humidity, in contrast to graphite materials, and indicate that nanotubes could be utilized as both low and high frictional surfaces.     

Investigation of Electrical Characteristics of Thin Silicone–Carbon Coatings

The complex resistance of silicone–carbon films of thickness more than 3 m is measured on the basis of an analysis of the electrotechnical substitution circuit containing a capacitor and a resistor. It was found that the parameters of the equivalent circuit determined experimentally make it possible to estimate whether the film thickness is greater than 3 m or not, i.e., to measure the film thickness more than 3 m. In this case, at frequencies higher that 100 kHz only the capacitive component of the impedance can be measured, whereas the active component associated most likely with the presence of silicon carbide in the film material was detected at lower frequencies. It is shown that for carrying out similar experiments with thinner coatings it is necessary to use a probe covered by a dielectric material with the higher dielectric constant.     

A Helical Magnetic-Cumulation Generator with a Compact Transformer

Experimental data on a helical magnetic-cumulation generator with an output step-up transformer formed by two coaxial solenoids is presented. The inner diameter of the helix is 50 mm. Compared with the transformers described earlier, this transformer has a smaller size. The transformer can feed an energy of 1 kJ into a 100-H high-impedance load.     

A Multifunctional Microwave Gunn Oscillator for Magnetic Resonance Spectroscopy Applications

A waveguide Gunn oscillator operating in the 12-mm wavelength range, in which the gyromagnetic frequency tuning is carried out using a FeBO₃ antiferromagnetic single crystal, is described. To increase the output power, the pulsed power supply of the Gunn diode is employed. In the case of a microwave pulse duration of 0.1–50 s and off-duty factor of no less than 200, the pulse output power reaches 1.3 W (in the continuous mode, it is 0.3 W). The generator is developed for magnetic resonance spectroscopy applications in order to solve a wide circle of problems, including investigations of the nonlinear spin dynamics of magnetic materials and study of spectra of optical magnetic-resonance detection.     

The Boundary Lubrication Properties of Model Esters

The friction of three chemically distinct esters was measured in order to determine how molecular architecture influences friction. The friction coefficients of mica surfaces separated by a thin film (<2 nm) of -chlorodecyl benzoate, -chlorodecyl pentafluoro benzoate, and -chlorodecyl perfluoro hexanoate were measured to be 0.15±0.015, 0.13±0.012, and 0.12±0.02, respectively. The friction coefficients for the esters are lower than the previously measured friction coefficients of simple hydrocarbon liquids such as n-tetradecane (=0.8), but are comparable to the friction coefficients of surfactant monolayer coated surfaces (=0.001–0.2). The results suggest that the ester molecules adsorb onto the mica surface with the (phenyl or hexyl) carbonyl next to the surface and the hydrocarbon tail pointing away from the surface. Hence, the friction is controlled by the packing density and properties of the hydrocarbon tail. Changes in the chemistry and structure of the carboxylic acid portion of the ester only give rise to small changes in the friction coefficient.     

Investigation of electrostrictive polymers as actuators for mesoscale devices

Abstact This paper presents an investigation of the use of electrostrictive silicone polymers as actuators for mesoscale devices. The generated strains of both flat and rolled actuators, based on Dow Corning Sylgard 182 and 184, with sputtered gold electrodes, are presented as functions of the applied electric field. Variables examined in this study include silicone film thickness, gold electrode thickness, cycling of the applied electric field, and actuator configuration (flat or rolled). In general, thinner silicone films and gold electrodes yielded greater strains, at a constant applied field. The actuator performance tended to deteriorate with repeated application of the electric field, and the gold electrodes cracked after being subjected to a large percentage strain.Nomenclature A Cross sectional area, mm² - a ₁ , a ₂ electrostrictive constants, m²/V² - D diameter, mm - E electric field, V/m - _o permittivity of free space, F/m - dielectric constant for silicones, F/m - F force, N - J work, J - l length, m - S _ij strain tensor, dimensionless - S _ijkl tensor of elastic compliance coefficients, m - t thickness, m - T _kl stress tensor, Pa - u _i displacement vector, mm - V volume, mm³ - Poisson ratio, dimensionless - w width, m - Y Youngs modulus, Pa     

A Switch Based on Reverse Switch-on Dynistors with a Diode Sharpener of Switched Current Pulses

A principle of constructing a combined semiconductor switch based on a diode assembly and an assembly of reverse switch-on dynistors (RSDs) is considered. The diode assembly serves as a sharpener of current pulses switched by the RSD assembly. The results of tests of a combined switch, which forms 3.5-kV voltage pulses with a duration of 1 s and a rise time of 10 ns at a load of 10 , are presented. Ways of enhancing the switching capabilities of RSD switches with diode sharpeners are presented.