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.     

A Low-Threshold Discriminator for Resistive-Plate Chambers

A low-threshold amplifier–discriminator (AD) is intended for reading information from resistive-plate chambers (RPCs) and consists of a preamplifier and discriminator. The minimum operation threshold of the device is 60 V at an input impedance of 25 , which corresponds to a charge of 0.12 pC induced on a strip. The AD time jitter is below 0.6 ns over an input signals range of (2–20)U _thr. The preamplifier noise referred to the input is <25 V (rms). The AD was developed for testing RPCs for the ATLAS (CERN) experiment.     

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 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 Mediator Spectrometric Unit

The mediator unit (mediator) generates a strobe pulse when a scintillation signal is at its maximum (peak moment). The strobe pulse starts the analog-to-digital converter, which performs digitization on a special command. The parameters of the mediator circuit presented are optimized to handle the signals from the detection unit, which comprises a CsI(Tl) scintillator, a silicon p–i–n photodiode, and a squaring amplifier. The maximum input-signal amplitude is 5 V, and the time of rise to the maximum is 7 s (quasi-Gaussian signal). When such signals are used, the strobe pulse is shifted in time with respect to the signal peak by 5 ns if the amplitude of the analyzed signals varies from 5 to 0.2 V. The unit is tested in operation (with minimal circuit alterations) over a rise-time range from 1 s (NaI(Tl)) to 20 s. The mediator includes a baseline-potential restorer and an adjustable-threshold comparator. Owing to these features, the mediator can also be used as an amplitude integral discriminator and can operate from signal sources with unstable base levels, including systems that require a signal time lock. When the recorded signals are superimposed on the leading and trailing edges, a considerable part of the superimposed signals is rejected.     

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.     

An Infrared Camera Based on Schottky Barriers for Daytime Observations of Stars

The daytime-sky background spectrum is analyzed. It is shown that the spectrum has a minimum in the vicinity of 2.5 m, which is close to the position of the peak of the spectral characteristic of elements of an array based on PtSi Schottky barriers. The optical layout of an -26 telescope with a built-in IR camera and an alignment channel is presented. The technique of adjusting the IR camera as a part of the telescope is described. The threshold sensitivity of the system, which consisted of the telescope with a 600-mm-diameter lens and an IR camera based on PtSi Schottky barriers, was experimentally measured in the spectral region of 1.2–3.3 m and was found to be equal to three stellar magnitudes.     

A Shipborne Laser Fluorimeter for Studying Sea-Water Fluorescence Spectra

A shipborne laser fluorimeter making it possible to determine promptly the concentration of chlorophyll A in sea water is described. The measurement error is 35% at chlorophyll concentrations of 0.1–3 g/l, and the single-measurement duration is 1 min.     

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 Stable Temperature Sensor Based on GaAs Structures with Schottky Barriers

The current–voltage and temperature–voltage characteristics of a GaAs structure with a Schottky barrier were measured, and their dependence on technological factors and temperature were determined. The main technological parameters of the device (the concentration of free carriers n ₀ in the base of diodes, the area S of the contact of the barrier-forming metal, and the value of the direct current I through the structure) were optimized. As a result, an element with a highly linear temperature–voltage characteristic was obtained. For Pd–GaAs structures with S 0.32 mm² (d 640 m), I 10 A, and n ₀ = (1–3) × 10¹⁶ cm^–3, the thermal sensitivity coefficient is 2 mV/°C, and the nonlinearity coefficient is < 0.5% within a range of 100 K, which is much lower than obtained theoretically. A highly stable temperature sensor is manufactured on the sensitive element offered.     

Effect of surface contamination on the UHV tribological behavior of the Cu(111)/Cu(111) interface

Friction and adhesion measurements have been made using two Cu(1 11) samples modified by the presence of atomic adsorbates. Copper surfaces with 10–15 Å thick contaminant films resulting from exposure to the atmosphere exhibited a static friction coefficient of _s = 0.75 ± 0.18. A sharp increase in the friction coefficient was observed when the contaminant layer was reduced to submonolayer thickness by sputtering and for the cleanest Cu(111) surfaces studied the static friction coefficient was _s = 4.4 ± 1.3. To further investigate the tribological effect of submonolayer coverages of surface contamination adhesion experiments were performed using surfaces modified with sulfur adsorbed at coverages in the range _s = 0.0–0.39 ML (saturation). The adhesion coefficient of the clean surfaces (_ad = 0.69 ± 0.20) was markedly reduced by the presence of 0.05 ML of sulfur and decreased monotonically with increasing sulfur coverage to a limiting value of _ad = 0.26 ± 0.07 at _s = 0.39.     

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 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.     

Detection of the Increment of an Instantaneous Phase in a Long-Base Laser Meter of Small Vibrations

A phase meter for processing signals of a laser meter of small displacements and vibrations at long base distances is described. Vibrations of objects are transformed into small increments of a signal phase at an RF carrier, which are detected by the phase meter and are outputted as signals proportional to microvibrations in the acoustic range. At a given carrier frequency f _c = 10.7 MHz, vibrations are detected within a band f = 3 kHz. Such vibrations produce phase fluctuations of 10^–42, which correspond to magnitudes of 1 nm for a laser wavelength 10 m.     

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 Two-Section Gas-Filled Ionization Chamber for Neutron Flux Measurements

A promising design of a -type two-section gas-filled ionization chamber is described for the first time. A relationship between the design parameters, gas pressure, and characteristics of the material is determined, under which full compensation of the background currents from the -radiation and the measurement of thermal neutron fluxes in a range of 400 to 7 ×10⁹cm^–2s^–1at a load characteristic with a 5% nonlinearity are provided. Test results of the chamber are presented.     

A Simple Method Producing Shadow Masks Used in Electrical Characterization Techniques

In this paper, a novel technique is introduced to make a shadow mask (SM) that is used in various electrical characterization techniques such as Hall-resistivity, magnetoresistance, and TLM (Transmission Line Method) ohmic contact measurements. By using this technology, a film thickness of about 0.25–0.30 m was obtained after photoprocessing. We reached an SM thickness of 15–20 m by electrodeposition, which is required for a sufficiently high toughness. It was observed that the sharpness of the masks was also fairly good. The SMs obtained using this technology have been successfully used in various applications.     

A Streak-Camera Neutron Monitor

The principle of a high-speed neutron monitor is based on neutron–proton conversion in a polyethylene converter. Protons thus produced are detected by an X-ray image-converter tube with a CsI photocathode. The monitor efficiency is 1.5 × 10^–3, its time resolution is 30 ps, and its spatial resolution is 100 m. The instrument is used to measure the time parameters of neutron fluxes in the ISKRA installations.     

Express Method for Control of Space–Energy Characteristics of Laser Radiation Using Al-VO2-D (Dielectric) Thermochromic Materials

-1 and -2 visualizers of optical radiation are described, whose screen is based on film-type reversible Al-VO₂–D thermochromic materials (D is a dielectric). By using a -2 visualizer, it is possible to perform the semiquantitative express analysis of the space–energy characteristics of pulse and continuous laser radiation at wavelengths of 0.3–10.6 m.     

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.