The development and use of scintillation chambers in nuclear physics

Imperial Users onl

Orbital transfer vehicle launch operations study: Automated technology knowledge base, volume 4

A simplified retrieval strategy for compiling automation-related bibliographies from NASA/RECON is presented. Two subsets of NASA Thesaurus subject terms were extracted: a primary list, which is used to obtain an initial set of citations; and a secondary list, which is used to limit or further specify a large initial set of citations. These subject term lists are presented in Appendix A as the Automated Technology Knowledge Base (ATKB) Thesaurus

The analysis and optimization of electrostatic electron optical lenses with rotational symmetry, through use of orthogonal functions.

Thesis (Ph.D.)-University of Natal, 1978No abstract available

Application of a novel CCD technology to medical imaging

This thesis describes an evaluation of a novel low light level charge couple device (L3CCD) technology. Two L3CCDs have been fully evaluated in terms of their signal and noise properties. The primary aim of this work is to identify the device characteristics that affect the overall performance. Conclusions have been made to this end and a prediction of the optimal performance in terms of the device sensitivity is made. Comparisons with other detectors suitable for use in medical imaging have shown that the L3CCD surpasses other detectors in specific performance characteristics and is comparable in others. The competitive performance of the L3CCD confirms that it may afford benefits in those areas in which the L3CCD has superior performance compared to other detectors. Two diagnostic imaging techniques which were identified as applications of L3CCD technology have been investigated. Linear systems analysis has been used to predict the performance of two L3CCD based imaging systems for use in fluoroscopic imaging. Comparison of the predicted performance of the two system with systems in clinical use show that an L3CCD coupled to an x-ray phosphor via a tapered fibre optic is a competitive alternative to present fluoroscopic imaging systems. Experimental validation of the model has confirmed this conclusion. An L3 detector has been designed, built and evaluated for diffraction enhanced breast imaging. To demonstrate the use of the L3 detector for diffraction enhanced breast imaging it has been used to acquire diffraction images of human breast tissue with cancerous inclusions. Measurements of scatter contrast confirm improvements in scatter contrast compared to transmission contrast. The successful demonstration of the L3CCDs ability to collect diagnostic information has shown that the L3CCD is suitable for diffraction enhanced breast imaging

The study of novel electrostatic electron lenses

This thesis is concerned with the investigation, both numerically and experimentally of novel electrostatic lenses. The properties of a five-element lens are described. This lens allows the variation of the magnification of an image of fixed position with fixed overall energy, and can be therefore considered a 'zoom' lens. This lens can also be constrained so that it is afocal and the separation between any pair of conjugate points is constant, and therefore independent of V5/V1, with the magnification related very simply to V5/V1. A numerical technique involving matrix multiplication is used to compute the properties of the five-element lens from the tabulated properties of two-element lenses. Manipulation of the calculated data revealed that it is possible to define two 'universal' curves to summarise its properties. The calculated lens properties are compared with those previously obtained by experiment, (Heddle and Papadovassilakis 1984). The aberration behaviour of a five-element lens was investigated. In particular, the dependence of the spherical aberration coefficient Cson V3/V1 where V5/V1 = 1, and V2/V1 = V4/V5. Cs was also investigated for a number of afocal lenses. Finally, Cs was investigated for the lens where V5/V1 = V3/V1 = 1, V2/V1 is the variable and V4/V3. This lens was found to have a minimum value for the product MAG x Cs, therefore, optimum values of V2/V1 and the magnification exist for this lens. The values for Cs obtained by experiment are compared with those calculated by my supervisor Professor Heddle using the Bessel Function Expansion Method, and the Fox-Goodwin Method. Finally, the properties of a three-element lens constructed from 31 discs electrically insulated from each other, and sandwiched between two ordinary cylindrical elements was investigated. Voltages were applied to this lens so that it simulated a three-element lens with a 'movable' centre element of variable length. The obtained experimental properties are also compared with those calculated by Professor Heddle.<p

Multi-Dimensional Quantitative Laser-based Diagnostics - Development and Practial Applications

Laser based optical diagnostic methods are routinely used in combustion research. Many of the more common approaches are based on illuminating a cross-section of the sample with a thin laser sheet. For example, by targeting an electronic transition in a molecule, its concentration within the plane illuminated by the laser sheet can be deduced. By probing the relative occurrence of an atom or molecule in different rotational or vibrational states or by probing the Doppler shift in Rayleigh scattering, it is possible to extract the temperature. The flow field can be measured by seeding particles into the measurement volume and following them through multiple exposures. The work reported in the thesis concerns the development, improvement and applications of measurement techniques based on laser sheet illumination. The aforementioned techniques are most often employed on a single shot basis, providing independent snapshots of two-dimensional (2D) data. In some examples, the measurement techniques are extended to the third spatial dimension, and in recent years, studies employing high repetition rate measurements capable of resolving the dynamics in time have become more frequent. In the thesis, a method for simultaneously extending the measurements to the third spatial dimension and to the time dimension, is presented. A high repetition rate laser and detection system is combined with oscillating mirrors, the laser sheet being scanned back and forth throughout the measurement volume. The deflections from two mirrors operated at different frequencies are combined to obtain equidistant laser sheets in the measurement region. The method is demonstrated on the Mie-scattering from a flow of droplets and is used to probe the planar laser induced fluorescence (PLIF) from the OH in a flame. Post processing methods to calculate concentrations and flame-fronts from large data sets are demonstrated. Measurements of droplet concentration and size distribution in sprays, based on recording the light scattered from a laser sheet, suffer from uncertainties due to multiple scattering (MS) and attenuation of the illuminating and scattered light. A method is demonstrated here, that takes advantage of the ability to suppress the MS light by means of structured illumination. After MS suppression, the attenuation of the laser and signal light can be compensated for by comparing the transmission through the spray with the side-scattered signal. In the process, the local extinction coefficient is calculated from the Beer-Lambert law. Laser based optical diagnostic techniques are in general developed for atmospheric flames under ideal laboratory conditions. In the application of the same techniques in more realistic situations, such as internal combustion (IC) engines, the harsh conditions involving vibrations, varying pressure, moving parts, limited optical access and a sooty environment have to be taken into account. Several of the measurement campaigns reported in the thesis were conducted in IC engines. Although the main goals of these campaigns were to answer combustion or engine related questions, time has also been invested in improving and adopting the measurement techniques to the existing conditions. By following the spray propagation in a light duty-diesel engine over time, knowledge was gained regarding how early spray injections should be conducted to avoid wall wetting. From high speed laser induce incandescence (LII) measurements in a heavy-duty Diesel engine, conclusions regarding soot formation and oxidation were drawn. The implementation of LII at high repetition rates in IC engines was investigated here. Challenges associated with attenuation of the laser and signal light were also addressed. Visualization of the flame jet propagation in a large-bore gas engine was made possible by means of fuel tracer LIF. Apart from the combustion related conclusions, it was shown that the image quality could be improved substantially by the use of correction optics