Table of contents

Discusses the parameters of the gas discharge pertinent to its display applications, and describes the construction, operation and present 'state of the art' of plasma panels. Especial attention is drawn to the current research on the application of plasma panels to television with their potential as the 'picture-on-the-wall' set of the future.

A manipulator for use in vacuum systems is described. It provides independent translation in three orthogonal directions with a range of 4 mm in each direction and a positioning accuracy of +or-5 mu m. It has been used to position targets at the focus of a high power laser beam.

It is shown how an optical multichannel analyser associated with a low dispersivity spectroscope can offer a real time view of a low level luminescence emission spectrum. Direct observations support the quantum model. The authors previously proposed (Phys. Stat. Solidi, vol.30, p.279) to explain wide band photoluminescence in SnO₂ single crystals.

The design and the construction of an apparatus for measuring the Hall effect in ultrahigh vacuum conditions is discussed.

The design of a simple, versatile rotatable cryostat for magnetic resonance studies in the range 2-300K is described. A special tail assembly permits conduction-cooling of samples with minimal helium consumption at low temperatures, accommodates both single crystal and powder specimens, permits optical irradiation of samples in situ, and allows samples to be investigated conveniently with a commercially available e.p.r. cavity and wide-line n.m.r. probe.

It is shown that Rayleigh waves can be generated and received by the electro-acoustic method. The conversion factor is sufficient for the technique to find application in low power ultrasonics.

The use of wide aperture channel electron multipliers for the detection of ultraviolet radiation is described and the performance of similar Mullard and Bendix tubes compared. In particular, it is shown how the efficiency of these detectors can be improved by biasing a grid placed close to the entrance cone, but this improvement is achieved only at the expense of timing resolution. These characteristics are interpreted in terms of ejection of secondary electrons near the cone periphery.

Experimental techniques are presented for (i) a very simple zone melting technique employing a floating zone maintained by an arc which allows preparation of high purity single crystal cathodes, and (ii) a grinding device which allows the LaB₆ tips to be ground to a radius of curvature of less than 3 mu m using a metallurgical polishing wheel.

Using commercially available fibre optic material, a simple but effective device has been constructed which allows high resolution optical spectroscopy on rare earth compounds at liquid helium temperatures, in magnetic fields up to 15 T. The advantage of this device is that it allows an optical experiment to be performed in a helium Dewar without windows.

The construction and some of the operating characteristics of a multichannel, laser triggered spark gap (LTSG) are described. Simultaneous subnanosecond switching in five channels of up to 10 kV is possible, making the LTSG an ideal master switch for pulsing Pockel cells to control the pulse shape and isolation necessary in a large laser oscillator-amplifier system. Operated under N₂ at a pressure of approximately 10 kTorr the LTSG had a risetime <300 ps and used in conjunction with a fast Pockel cell switch could shutter reliably optical pulses of <or approximately=500 ps duration from the output of a Q-switched laser. The results indicate that at higher pressures the risetime of the LTSG should be further reduced allowing switching in approximately 100 ps to be achieved.

An inexpensive, sensitive pyroelectric bolometer for use as a fast neutral beam detector is described. Experimentally determined responsivity and noise equivalent power are presented, and are shown to agree with theoretical predictions. The detector has been used to measure the power absorption coefficient and the secondary electron ejection coefficients for 150 eV to 10 keV hydrogen and helium atoms impinging on a silver surface.

The approximation of using third order spherical aberration coefficients to represent the combined effects of all the third order aberrations of electrostatic lenses is investigated and the range of validity and accuracy of the approximation is examined.

A slit-servo-system is described which maintains the output of an optical monochromator at a constant level as the wavelength is scanned. The system has been developed for infrared excitation spectroscopy, but would also be applicable to double-beam absorption or reflection spectroscopy. Part of the optical radiation from the monochromator is directed to a thermocouple detector which is assumed to have a black body response over the wavelength range of interest. After amplification the signal from the detector is compared with a reference voltage and the error signal is converted to a frequency. The series of pulses drives a d.c. stepper motor coupled to the monochromator slits, and as balance is reached the motor slows down, thus preventing overshoot.

A method for detecting particles and measuring velocities in an atomic beam is described with experimental results, using high power optical pumping with a tunable c.w. dye laser. Simultaneous detection and velocity analysis is achieved by detecting the resonance fluorescence and measuring the Doppler shift of the excitation frequency. Expressions for the detection efficiency (being around unity) and the velocity resolution (being approximately 60 m s^-1, independent of nu ) are given and verified experimentally for Na atoms.

An electronic frequency sweep generator that eliminates the need for mechanical frequency scanning in nuclear quadrupole resonance (NQR) spectrometers is described: In addition to overcoming the disadvantages inherent in any mechanical system, the new approach can facilitate the use of automatic scanning and data acquisition, paving the way for the application of time-averaged signal recovery techniques. In addition to its application to NQR the generator has a wide range of applicability to systems where motor driven potentiometers are used but are either inadequate or inflexible.

Following the work of Geerk and Thomas (1971), a magnetic analyser of high dispersion with improved performance was built. In particular, the better resolving power has been obtained by increasing the angular dispersion D and reducing the relative energy inhomogeneity Delta U/U of the ion beam. This should allow one to analyse ions up to 150 u.

A magnetic spectrometer of the Castaing-Henry type has been incorporated between the objective and intermediate lenses of a conventional 100 keV transmission electron microscope (AEI EM6). The electron optics of the spectrometer were adjusted to give semistigmatic focusing, allowing an overall energy resolution of 2 eV in spectra and energy selected images. Making use of the hysteresis properties of the magnetic circuit, energy-selected diffraction patterns are also obtained, with an energy window of about 8 eV. An electron counting system was incorporated to allow accurate recording of energy loss spectra. A simple Zener diode circuit is described, which provides calibration of the energy loss to within +or-0.2% for losses up to 690 eV.

The characteristics of electron guns with tungsten filaments are investigated in some detail, with particular reference to their use in electron probe instruments, and an improved method of measuring brightness is described. Consideration is given to the conditions that must be fulfilled if optimum performance is to be obtained and it is shown that current densities as high as 10 A cm^-2 can be drawn from the tip of the filament without exceeding a total gun current of 1 mA.

To visualize and measure quantitatively flow velocity distributions, a luminescence method which uses a pulse light was investigated. A method by which flow velocity can be measured regardless of the widths of excitation time and photograph exposure time was developed. Some optical and fluid characteristics of glycerin aqueous solutions in which luminescence particles are well dispersed are reported. The spatial resolving power of this method was found to be 100-300 mu m. The apparatus which has mechanical shutters with rotating discs was used to measure the velocity distribution of two-dimensional flows.

A method is described for the preparation of a large unbacked, ultrathin metal window covering a hole in a disc. The metal adheres directly to the disc forming a helium-tight partition. An aluminium window with a thickness of 0.1 mu m and 6 mm across was strong enough to withstand a pressure difference of 80 Torr. These windows are suitable, for example, for transmitting shortwave UV radiation from a helium discharge lamp.

The design of a high performance low cost device for measuring the outputs from strain gauge transducers is discussed. The instrument is an AC excited current injection nulling type with automatic quadrature rebalancing. Three channels of this equipment have been constructed and used to measure the outputs from a force balance in a transonic wind tunnel. An accuracy of better than 0.1% of full scale was obtained along with a resolution of 0.1 mu V. The instrument also has excellent electrical noise rejection characteristics and is unaffected by thermal EMFs.

The risetime of a small thin foil coaxial shunt has been reduced to that of the available measuring equipment, namely 300 ps. The crucial effects of finite pulse transit times in the shunt are demonstrated. In the optimum design risetime is independent of shunt length and the pulse transit time can exceed the risetime. The intended main application of the shunt is to measure the risetime of Pockel cell switching pulses used in a high power neodymium laser.

Migration, the movement of one component in a matrix of another, is a phenomenon well known in the paper, plastics, printing and other industries. Because of the thin films generally involved, migration over short distances can result in large changes in certain properties. This paper describes the use of a modified interference microscope to measure adhesive distribution in a layer of pigment coating on paper. The modifications to the standard instrument are described. The technique described allows far greater accuracy and precision in the measurement of phase changes than previous visual methods. It may be readily adapted to the examination of other thin films.

The characteristic equation of an odd-order phase sensitive detection system for the determination of a resonance frequency is derived. Reference to a particular case is used to show that the system is capable of high accuracy when operated in the high-pass derivative filter mode.

Obtains the solutions to the problem of adhering conducting spheres by treating it as a simple boundary value problem of two separated spheres in the limit of zero separation.

Describes an apparatus which allows the spectrophotometric cells to be immersed in coolant water. It is relatively inexpensive and easy to fabricate.