Table of contents

A new reciprocating wear testing rig is described that has been designed, built and commissioned at the Berkeley Nuclear Laboratories (BNL). The objectives of this work are to improve upon the range of parameters offered by the existing rigs and to provide additional facilities for data acquisition and analysis.

The author describes the development of a probe method of measuring thermal conductivity k, to enable one to obtain k at times t before the linear domain of probe temperature against ln t is properly established. A variety of probe structures can be accommodated. A probe was constructed and the experimental procedure plus the associated analysis (using a simulation model PROBE) was verified by making measurements on materials of known properties. The technique was applied to an unconsolidated coarse granular medium, a pebble bed consisting of graded river pebbles with equivalent spherical particle diameters 24+or-7 mm, and a bed porosity of 0.396.

A simple but original system is presented which allows for transmitting optical data via fibre lightguides to and from the inside of a high-pressure vessel at up to 200 MPa. Details of the design and results or preliminary performance tests of the system are discussed.

A single-crystal diamond anvil cell is described which has been successfully cycled down to liquid helium temperatures in numerous experiments. Superconducting transitions are detected by a low frequency AC technique employing a radially compensated gradient coil and a commercial RF SQUID system. The pressure is determined at room temperature by the ruby fluorescence technique with a focused laser beam. Pressure changes between room temperature and low temperature are minimised. A recalibration of the superconducting critical temperature, T_c, of Pb as a function of pressure has been carried out. The so-called Pb manometer turns out to be a very suitable pressure gauge up to about 30 GPa. At higher pressures the T_c of Pb is suppressed below 1.2 K and hence, for normal purposes, is inconveniently low. At the present limit of resolution the Pb I-II phase transition at 13 GPa is not reflected in the smooth T_c-P dependence.

The development of an electronic power factor meter to replace conventional electrodynamic types is described. The design is based on an analogue-to-digital converter (ADC) provided with ratiometric facilities. A signal proportional to the peak voltage (V_m) is applied to the reference input voltage of the ADC, while another signal proportional to the product of the peak voltage (V_m) and power factor (cos phi ) is applied to the analogue input. The result is a power factor reading.

The authors have measured the inductance and resistance of a self-triggered spark gap as functions of the interelectrode distance and the pressure. The switch was designed to drive, at high repetition rates, the Blumlein circuits of nitrogen lasers (capacitances and voltages were of the order 1 nF and 10 kV). The pressurisation resulted in a large decrease in resistance but left the inductance almost unchanged.

Most modern astronomical photometry measurements are carried out with small digital computers. The speed with which the system can be run is usually limited by the input interface and the duration of any real-time routines required to route data-flow and oversee on-line storage. A new system that uses external memory and a hardwired Address Vector Generator is described and shown to obviate this problem.

A simple method for correcting the photoconductivity excitation spectrum is suggested. The method consists of illuminating the entrance slit by the light of a standard tungsten lamp run at a known colour temperature (2080 K in the present investigation) reflected from a MgO screen placed at an angle and recording the reflected light with the photomultiplier tube. The sensitivity factor is determined from the ratio of observed photomultiplier response and the intensity at different wavenumbers calculated from Planck's law for the colour temperature and multiplying by the reflectivity of MgO in the visible region. The spectrum of CdS agrees accurately with results reported previously.

The authors report extension of the spectral range of fluorescence decay time measurements up to 930 nm using spark source excitation, time-correlated single-photon counting and a low-noise detection system incorporating the Philips XP2257B photomultiplier.

The authors describe an absorption cell suitable for recording infrared spectra. The optical path can be adjusted between 1 and 10 m. The temperature is variable in the range 200-400 K. This stainless steel cell has been especially designed for ozone. A 10 mu m ozone absorption spectrum is presented as an example.

Describes a mass spectrometer, gas inlet and operating protocol which have been developed for the purpose of making stable isotope measurements of subnanomole quantities of nitrogen gas. The mass spectrometer achieves high levels of sensitivity by operating in the static vacuum mode; the levels of precision attainable have been assessed in a number of ways. The instrument is capable of obtaining comparative nitrogen isotopic compositions ( delta ¹⁵N values) to a precision of +or-0.24⁰/₀₀ from samples of 0.4 nmol, as determined from a zero-enrichment test performed throughout a single day on 40 consecutive samples. The absolute accuracy of the method, as derived from measurements on samples of known isotopic compositions, is about +or-0.5⁰/₀₀. The instrument was designed to work routinely with samples of between 0.07 and 0.4 nmol of nitrogen but is demonstrated that the equipment can handle 20 pmol quantities of gas. The performance is difficult to quantify at these low levels since the inlet system does not have the facility to reproducibly introduce such small gas samples.

Describes a technique for the extraction and purification of sub-nanomole quantities of nitrogen for stable isotopic analysis. The procedures described are intended for use with a high-sensitivity static vacuum mass spectrometer such as that describes by Wright et al. (1988). It is essential that low nitrogen blanks are obtained during the sample treatment; it can be demonstrated that contributions of nitrogen from the extraction and subsequent gas handling procedures can be limited to as little as 0.021 nmol. Experiments are described to verify that species such as CO₂, CO and CH₄, which would otherwise interfere with the nitrogen isotopic measurements, can all be removed during the purification operations. A study of the difficulties which might be encountered if some nitrogen were converted to nitrogen oxides has also been undertaken. It is concluded that N₂O would be totally decomposed to the elements during purification but nitrogen in the form of NO and NO₂ is only partially recovered. A method for investigating whether nitrogen oxide production is a real problem during the analysis of geological samples has been devised. Some examples using the technique are presented.

A simple method of producing a timed beam of ortho-positronium (o-Ps) atoms by utilising positron-gas-atom collisions is described. The technique has been used to demonstrate that the beam is tunable and to estimate its energy.

A shock tube method to determine the acoustic non-linear parameter B/A of liquids is described. Experimental results for ethanol, methanol, diesel and water are given.

The construction of a new capillary flow viscometer capable of measuring the viscosities of corrosive gases up to pressures of 0.1 MPa is reported. The theory and calibration of the apparatus is described, and the accuracy of the apparatus demonstrated by means of relative measurements of the viscosities of argon and carbon dioxide.

A differential viscometer, the first of its kind, to measure small differences in viscosities of two liquids has been developed using the principle of the well known rotating cylinder viscometer. Two rotating cylinder viscometers, with their inner cylinders connected by a common suspension and the outer cylinders rotating with the same speed but in opposite directions, have been employed. With liquids of the same volume and viscosity the torques applied on the inner cylinders are equal and balanced. The unequal torque experienced by the cylinders due to any difference in viscosities in two samples has been measured by a standard lamp and scale arrangement with a mirror attached to the common suspension of the inner cylinders. Representative results obtained with different grades of silicone fluid show that the instrument is capable of measuring differences in viscosities as small at 4%.

Liquid metal infiltration techniques for producing metal-matrix composites offer economic advantages. To date metal-matrix composites produced by casting have been limited to low-temperature metals such as Al, Mg and Pb because of the serious problems inherent in high-temperature casting. A technique and apparatus is described which has permitted the production of fibre-reinforced NiAl/Al₂O₃ and Ni₃Al/Al₂O₃ composites. The technique involves liquid metal infiltration of Al₂O₃ fibres under gas pressure.

A recirculating wind tunnel is described that provides a controlled convective and radiative environment for energy metabolism studies with animals. Simultaneous regulation of air temperature, wind speed and short-wave irradiance is achieved. The physical conditions can be maintained for at least 24 h. Flow straighteners lower wind turbulence in the small-sized tunnel. Wind tunnel volume is minimised to facilitate steady-state measurement of respiratory gases.

An optoisolated driver unit for spark-gap-controlled home-made TEA excimer lasers is described. The unit has been shown to give repetitive discharges of 40 nF capacitors at 30-40 kV in 10-20 ns times without the problems and failures of earlier designs.

A UHV metal cell and a sample holder for infrared investigations of solid catalysts are described. The cell and holder are designed for use with spectrometers requiring large samples. The catalyst layer is pressed into a metal grid and its size is limited only by the diameter of the insert tube. The grid serves simultaneously as a sample heater, and it was verified that linear heating and cooling characteristics are obtained when applying voltage through a motor-driven transformer.

A technique for measuring local microscopic currents in high-temperature superconductors is presented. The technique employs a scanning electron microscope to provide a narrowly focused beam of electrons, giving rise to a current in the sample which is placed in a cooling stage. The locally induced voltage is detected by external electronics.

Presents an apparatus for performing a true 3D electron spin resonance image reconstruction at low microwave frequency (1.3 GHz). The gradients G_zz, G_zx, G_zy of the field B_z along the three perpendicular axes are directly controlled by a personal computer which is also used to store the converted signals and to compute the spin-density function from the projections. The mathematical technique used is a filtered projection obtained by means of the Fourier transforms, called 3D Fourier reconstruction. Examples of signal reconstruction on phantoms are given.

Unknown frequencies of integrated-circuit interconnections are measured with an accuracy of 1 Hz by an extension of the frequency mapping proposed by Brust and Fox (1984, 1985). The oscillation frequency of a substrate bias generator in a 1M DRAM is measured as a function of the supply voltage.