Table of contents

A review is given of experimental techniques and instrumental design of field ionisation and desorption sources. Special emphasis is laid on a comprehensive account of the various types of ion emitter. Different sample-loading techniques are also discussed. Automatic FD emitter-heating devices and laser-assisted FD are also described.

A system for the simultaneous recording of 20 analogue signals is described. One hundred points of each input signal are recorded at 1 mu s intervals using fast analogue multiplexing techniques. All data are digitally stored by a transient recorder and may be processed on-line by a computer. Possibilities of modifying the number of input channels, the time between the samples in each channel and the total recording times are discussed.

A computer-assisted system for digitising images, either photographed with a TV camera or previously recorded on a video tape, is described. It is composed of standard elements and permits on-line densitometry analysis of pictures at a relatively low cost. Results obtained with this system in laser beam profile and focusing analysis are presented.

A waveguide mount for a millimetre wave glow discharge detector is described. The mount design is characterised by a simple tuning mechanism permitted by the unique properties of the glow discharge detector. Results of responsivity and signal-to-noise measurements at 70 GHz are presented and compared with a conventional millimetre wave crystal detector.

The housing described provides for precise positioning of the detector at the optical focus. At the same time the detector is well protected from thermal fluctuations in the environment by a totally evacuable enclosure. Use of this module has given twofold improvement in signal-to-noise ratio in typical experiments.

Describes how the gain of a superconducting chopper amplifier can be stabilised by the application of negative feedback. The circuit has the additional advantages of high input impedance and excellent linearity.

Describes modifications made to a simple limiting oscillator circuit useful for magnetic resonance measurements in metals. These modifications have resulted in an increase of signal-to-noise by a factor of 20 for radio frequency size effect measurements.

Spatial filtering of the Fourier transform of a newspaper picture is achieved using a photographic negative of the Fourier transform generated by illumination of a small portion of the object. The results show improvement over those of simple pinhole spatial filtering. Also described is the use of photographically reduced array of dots as a spatial filter, giving slightly inferior results but greater flexibility of use. The optical system used incorporates a 2 mW He-Ne laser as the source.

A servomechanism capable of moving a microscope slide in a plane to precision of better than ¹/₈ mu m over a field of up to 50 mu m square is described. Its purpose is to provide a scanning movement for an optical densitometer with a fixed, on-axis light spot. The scanning velocity can reach a maximum of 10 mm s^-1. The instrument is designed to be controlled remotely (by computer) and to be both compact and lightweight.

Experimental investigation of an X-ray densitometer using K-line-emitting Cr and Al anodes with tube voltages of about 18 kV and tube currents of as much as 1 A are described which show an improved sensitivity and quantum flux. These results are in agreement with a theoretical model presented. In an SF₆ shock wave experiment densities down to 8*10^-2 kg m^-3 are measured with the Al anode and an accuracy of about 15% and a time resolution of 5 mu s. With the Cr anode the accuracy is better than 10% for densities of 4*10^-1 to 5 kg m^-3.

A method of measuring refractive index increments for macromolecules in solution using holography is described. The method is effective for refractive index changes of the order of 10^-4 and is very linear. Measurement results on five macromolecules, four proteins and one detergent, in physiological salt solution at 632.8 nm using holography and a commercial instrument, are presented.

The design and performance of the gun are discussed. Studies of small versions of the gun with a beam area of 1500 mm*30 mm provide design data for devices with beams covering 1 m in length and 25-100 mm in width. At beam energies up to 160 keV, the current density range is 1-2000 A m^-2 and pulse lengths vary from 100 to 10 mu s. Main features which contribute to the convenient use of these guns are the robust, demountable accelerating stages and the auxiliary discharge system.

By use of a modified laser Doppler anemometer set-up and a commercial digital correlator, velocity auto- and cross-correlation functions are measured directly. These functions determine time scales of velocity fluctuations as well as their first- and second-order statistics. The technique is demonstrated with flows of perfect time periodicity, i.e. Taylor vortices between rotating cylinders, and of a highly random nature, i.e. turbulence in an open flow channel.

A source is described which is capable of providing high intensity in the resonance lines of neutral and singly ionised metallic species, especially group II metals. Detailed analysis of the line profiles is presented which indicates that effects of self-absorption can be avoided in the source.

The instrument described is adapted to a 6.600 m concave grating with 1200 grooves mm^-1 and a ruled area 80 mm*20 mm. The grazing angle is 5 degrees , and the plate holder covers a wavelength range of 0-60 nm. A peculiar deviation of the focal curve from the Rowland circle is discussed. The lower limit of the grating reflectivity corresponds to approximately 3.5 nm, and good resolution is obtained. Improvements in the sliding spark technique are described.

An experimental system that is used to study the transmission of electromagnetic waves through a randomly ionised plasma is described. The primary advantage of the system is that the statistics of the propagation medium may be controlled and therefore repeated. Measurements of phase fluctuations suffered by transmitted microwave signals are used to study random propagation effects in plasmas having background pressures in the range 50-1300 Pa (0.4-10 Torr).