Thesis (PhD (Physics))--University of Stellenbosch, 2006. / This thesis is devoted to a study of the 93Nb( p r ,3He) and 59Co( p r ,3He) reactions at incident energies of 100 MeV, 130 MeV and 160 MeV. Double differential cross sections and analysing power distributions were measured from a threshold of ~30 MeV up to the kinematic maximum and at scattering angles between 15º and 120º. The experimental data were compared with theoretical calculations done by combining a statistical multistep theory with a deuteron pickup mechanism in the final stage. The contribution of the first three steps towards the total double differential cross section and analysing power was assessed. The theory described the experimental double differential cross section and analysing power data reasonably well over all incident and scattered energies and for both target nuclei. As the incident energy was increased, the characteristics of the reaction mechanism also remained consistent. Thus the results supported the underlying multistep-pickup theory. The two target nuclei demonstrated similar responses, suggesting these two share the same basic reaction mechanism. The total double differential cross section for the reaction dropped with an increase in incident energy. At a fixed emission energy, near the maximum allowed value, the slope of the double differential cross section increased with an increase in incident energy, resulting in the dominance of forward peaked reactions at higher incident energies. The sensitivity of analysing power to the multistep part of the reaction was valuable to the study. Forward-peaked contributions that were associated with single step direct reactions resulted in large analysing power values at small scattering angles, and values dropped to around zero at large angles. The analysing power also appeared to decrease to values approximating zero as the incident energy was increased to 160 MeV. Furthermore, this study also confirmed the dominance of higher step mechanisms at high excitation energies, irrespective of incident energy. In general the results were in agreement with the predicted properties of the assumed reaction mechanism at all incident and emission energies, which inspires confidence that the theoretical interpretation is likely to be correct.

Thesis (PhD)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: In this dissertation, we give an overview of disordered systems, where we concentrate on the theoretical calculation techniques used in this field. We first discuss the general properties of disordered systems and the different models and quantities used in the study of these systems, before describing calculation techniques used to investigate the quantities introduced. These calculation techniques include the phase formalism method used one dimension, as well as the scaling approach and field theoretic approaches leading to non-linear c-models in higher dimensions. We then introduce a complementary effective field theoretic approach based on the logarithmic derivative of the wave-function, and show how the quantities of interest are calculated using this method. As an example, the effective field theory is applied to one dimensional systems with Gaussian disorder. The average density of states, the average 2-point correlator and the conductivity are calculated in a weak disorder saddle-point approximation and in strong disorder duality approximation. These results are then calculated numerically and in the case of the density of states compared to the exact result. / AFRIKAANSE OPSOMMING: In hierdie tesis, gee ons 'n oorsig van sisteme met wanorde, waar ons konsentreer op teoretiese berekeningsmetodes wat in die veld gebruik word. Eerstens bespreek ons die algemene eienskappe van sisteme met wanorde en verskillende modelle en hoeveelhede wat gebruik word in die studie van hierdie sisteme, voordat ons die berekeningsmetodes beskryf wat gebruik word om die bogenoemde hoeveelhede te ondersoek. Hierdie berekeningstegnieke sluit in die fase formalisme wat in een dimensie gebruik word, asook die skalingsbenadering en veldteoretiese metodes wat lei tot nie-lineêr u-modelle in hoër dimensies. Ons voer in 'n komplementere effektiewe veldeteorie gebaseer op die logaritmiese afgeleide van die golffunksie, en wys hoe hoeveelhede van belang met hierdie metode bereken word. As 'n voorbeeld, word die effektiewe veldetoerie toegepas op 'n een dimensionele sisteem met 'n Gauss verdeling. Die gemiddelde digtheid van toestande, die gemiddelde 2-punt korrelator en die gemiddelde geleidingsvermoë word bereken in 'n swak wanorde saalpunt benadering en in 'n sterk wanorde duale benadering. Hierdie resultate word dan numeries bereken, en in die geval van die digtheid van toestande vergelyk met die eksakte resultaat.

Thesis (PhD)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: In this dissertation we set out to develop the first relativistic model for calculating complete sets of (p, 2p) spin transfer observables. In addition to this a new technique has been developed which allows us to evaluate the transition amplitude, which is used to calculate the scattering observables for the reaction directly. The influence of various modiuin-modificd parameters ()1I the scattered wave functions anr] NN interact ion lH-IVC' })('('11 invest igatcd DlIC t,C) (I,llIlJigllitic's surrounding the nNN coupling we have included both pseudosoalar and pseudovector coupling into the nucleon-nucleon interaction model. Furthermore we have included two different kinematic prescriptions to obtain the effective NN laboratory kinetic energy and center of mass scattering angle, which are used to obtain the NN scattering amplitudes. The aim of this study is to investigate the effects of the various model parameters on complete sets of scattering observables. Our investigation has shown that although the analyzing power is not very sensitive to nuclear medium effects, and the various other spin transfer observables such as Dnn should provide valuable insight. Further refinements of the model would be to include nuclear distortions as well as the IA2 model of the NN interaction. / AFRIKAANSE OPSOMMING: In hierdie tesis ontwikkel ons die eerste relatiwistiese model vir die berekening van 'n volledige stel (p, 2p) spin waarneembares. Verder word 'n nuwe tegniek ingevoer wat ons toelaat om die oorgangsamplitude, wat gebruik word in berekening van die verstrooings waarneembares vir die reaksie, direk te evalueer. Die invloed van verskeie medium-gemodifiseerde parameters op die verstrooide golffunksies en die NN wisselwerking word bestudeer. As gevolg van onsekerhede betreffende die лNN koppeling word beide die pseudoskalaar en pseudovektor koppeling in die nukleon-nukleon interaksie model ingesluit. Ons sluit ook twee verskillende kinematiese preskripsies in om die effektiewe NN laboratorium kinetiese energie en die massa middelpunt verstrooiings hoek, wat gebruik word vir die berekening van die NN verstrooiings amplitude, te bereken. Die doel van hierdie studie is om die effek van verskeie model parameters op 'n volledige stel spin waarneembares te ondersoek. Die studie toon dat alhoewel die analiseervermoë nie baie sensitief is vir medium effekte nie, die ander spin waarneembares soos byvoorbeeld Dnn waardevolle insig lewer. Daar word voorgestel dat die model verfyn word deur kerndistorsies as ook die meer algemele IA2 model vir die NN interaksie in te sluit.

Thesis (PhD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: A tunable narrow-bandwidth laser source combined with a supersonic gas jet as sample is wellsuited for obtaining high-resolution spectra of cold isolated molecules and complexes. In the present study such a laser source in the vacuum ultraviolet was applied to the spectroscopic investigation of rare carbon monoxide (CO) isotopomers and CO-noble gas van der Waals complexes in supersonic gas pulses seeded with natural CO gas. Tunable coherent vacuum ultraviolet radiation was generated by two-photon resonant fourwave sum-frequency mixing of two pulsed dye laser beams in a magnesium vapour medium. Laser induced fluorescence excitation spectra of the A(v'=3)-X(v"=0) vibronic band of CO molecules in a noble gas (neon or argon) jet were obtained by measuring the total undispersed fluorescence from the irradiated sample volume in dependence of the excitation wavelength. The dynamics of the flow-cooling process in the supersonic jet were investigated and the experimental parameters optimised using the rotational temperature of 12C160as determined from rotational line intensities. Rotational temperatures as low as 2 ± I K were observed. Spectroscopic detection of the rare 12C170and 12C180isotopomers was facilitated by the low rotational temperature and high spectral resolution. Six rotational lines of 12C170and four of 12C180were detected in the A(v'=3)-X(v"=0) vibronic band. This demonstrates the low detection limit (circa 3 parts per million) obtained in the experiment. The line wavelengths were determined to an accuracy of 0.2 pm using the well-documented 12C160and 13C160lines for calibration. The spectral results on 12C170are, to our knowledge, the first rotationally resolved laboratory measurements published on the A-X band of this isotopomer. Accurate wavelength data of the stable isotopomers of CO is of importance in the interpretation of astrophysical observations of CO in the interstellar medium. The newly determined 12C170wavelengths were successfully applied to a recent problem in astrophysics (Astrophys. J. Lett. 2003). The conditions in a supersonic jet facilitate the study of weakly bound van der Waals complexes, of which CO-noble gas complexes are prototypes. However, there is no experimental data available on the electronic excitation spectra of the CO-noble gas complexes, lying in the vacuum ultraviolet region. In the present experiment evidence of extensive complexation of the CO in the noble gas jet has been found, but in the spectral region around the A(v'=3)-X(v"=O) band of CO no distinct spectral features that could be associated with these complexes were observed. Having considered the existing knowledge on CO and CO-noble gas complexes and experimental studies on the excitation and dissociation dynamics of Iz-noble gas complexes, we regard complex induced inter-system crossing or electronic predissociation as the most likely causes for these observations. The results on the rare CO isotopomers demonstrate the potential of our experimental setup for high-resolution, isotope and state selective spectroscopy in the vacuum ultraviolet with a high sensitivity for fluorescent species. The availability of the now well-characterised experimental setup in our laboratory opens the way for further investigation of molecular or complex species with spectroscopic features in the vacuum ultraviolet region. / AFRIKAANSE OPSOMMING: Vakuum ultraviolet laser spektroskopie van CO molekules in 'n supersoniese gasstraal: 'n Afstembare smal bandwydte laserbron en 'n supersoniese gasstraal as monster is 'n geskikte kombinasie vir hoë-resolusie spektroskopie van geïsoleerde afgekoelde molekules en komplekse. In hierdie studie is so 'n laserbron in die vakuum ultraviolet gebruik in die spektroskopiese ondersoek van skaars koolstofmonoksied (CO) isotopomere en CO-edelgas van der Waals komplekse in supersoniese gaspulse wat 'n klein persentasie natuurlike CO gas bevat. Afstembare koherente vakuum ultraviolet lig is verkry deur twee-foton resonante vier-golf som-frekwensie vermenging van twee gepulseerde kleurstoflaserbundels in 'n magnesiumdamp medium. Laser-geïnduseerde fluoressensie opwekkingspektra van die A(v'=3)-X(v"=0) vibroniese band van die CO molekules in die edelgasstraal (neon of argon) is uitgemeet deur die totale fluoressensie van die beligte gasmonster, sonder golflengteskeiding, te meet as funksie van die opwekkingsgolflengte. Die dinamika van die vloeiverkoelingsproses in die supersoniese gasstraal is ondersoek en die eksperimentele parameters geoptimeer deur gebruik te maak van die rotasionele temperatuur van 12Cl60 soos bepaal uit die intensiteitsverhoudings van die rotasielyne. Rotasionele temperature tot so laag as 2 ± 1 K is waargeneem. Spektroskopiese waarneming van die skaars 12C170 and 12Cl80 isotopomere is moontlik gemaak deur die lae rotasionele temperatuur en die hoë spektrale resolusie. Ses rotasielyne van 12C170 en vier van 12C180 is waargeneem in die A(v'=3)-X(v"=0) vibroniese band. Dit demonstreer die lae deteksielimiet (ongeveer 3 dele per miljoen) wat bereik kon word. Die golflengtes van die lyne is bepaal met 'n akkuraatheid van 0.2 pm deur die bekende lyne van 12C160en 13C160vir kalibrasie te gebruik. Die resultate ten opsigte van 12C170 is sover vasgestel kon word die eerste rotasioneel-opgeloste laboratorium metings van die A-X band van hierdie isotopomeer. Akkurate golflengte data vir die stabiele CO isotopomere is van belang vir die interpretasie van die astrofisiese waarnemings van CO in die interstellêre medium. Die nuwe 12C170 golflengtes is suksesvol aangewend in die oplossing van 'n onlangse interpretasieprobleem in astrofisika (Astrophys. J. Lett. 2003). Die toestande in 'n supersoniese gasstraal maak die bestudering van swak-gebonde van der Waals komplekse moontlik. Hoewel CO-edelgas van der Waals komplekse as prototipes beskou word, is daar geen eksperimentele data beskikbaar oor die elektroniese opwekkingspektra van hierdie spesies, wat in die vakuum ultraviolet gebied lê, nie. In hierdie studie is daar eksperimentele getuienis gevind vir uitgebreide kompleksering van CO in die edelgasstraal, maar in die spektraalgebied rondom die A(v'=3)-X(v"=O) band van CO is geen duidelike spektrale kenmerke wat met hierdie komplekse geassosieer kan word, waargeneem nie. Na oorweging van die bestaande kennins oor CO en CO-edelgas komplekse en eksperimentele studies oor die opwekking en dissosiasie-dinamika van Iz-edelgas komplekse, beskou ons kompleksgeïnduseerde intersisteemoorgange of elektroniese predissosiasie as die waarskynlikste redes vir hierdie waarnemings. Die resultate oor die skaars CO isotopomere toon die potensiaal van ons eksperimentele opstelling vir hoë-resolusie, isotoop- en toestandselektiewe spektroskopie in die vakuum ultraviolet met uitstekende sensitiwiteit vir fluoresserende spesies. Die beskikbaarheid van hierdie nou deeglik gekarakteriseerde eksperimentele opstelling in ons laboratorium maak verdere ondersoek na molekulêre of kompleks-spesies met spektroskopiese kenmerke in die vakuum ultraviolet moontlik.

Thesis (PhD)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The fractional quantum Hall effect represents a true many-body phenomenon in which the collective behaviour of interacting electrons plays a central role. In contrast to its integral counterpart, the appearance of a mobility gap in the fractional quantum Hall regime is due entirely to the Coulomb interaction and is not the result of a perturbed single particle gap. The bulk of our theoretical understanding of the underlying many-body problem is based on Laughlin’s ansatz wave function and the composite fermion picture proposed by Jain. In the latter the fractional quantum Hall effect of interacting electrons is formulated as the integral quantum Hall effect of weakly interacting quasiparticles called composite fermions. The composite fermion picture provides a qualitative description of the interacting system’s low-energy spectrum and leads to a generalisation of Laughlin’s wave functions for the electron ground state. These predictions have been verified through extensive numerical tests. In this work we present an alternative formulation of the composite fermion picture within a more rigorous mathematical framework. Our goal is to establish the relation between the strongly interacting electron problem and its dual description in terms of weakly interacting quasiparticles on the level of the microscopic Hamiltonian itself. This allows us to derive an analytic expression for the interaction induced excitation gap which agrees very well with existing numerical results. We also formulate a mapping between the states of the free particle and interacting descriptions in which the characteristic Jastrow-Slater structure of the composite fermion ansatz appears naturally. Our formalism also serves to clarify several aspects of the standard heuristic construction, particularly with regard to the emergence of the effective magnetic field and the role of higher Landau levels. We also resolve a long standing issue regarding the overlap of unprojected composite fermion trial wave functions with the lowest Landau level of the free particle Hamiltonian. / AFRIKAANSE OPSOMMING: Die fraksionele kwantum Hall-effek is ’n veeldeeltjie verskynsel waarin die kollektiewe gedrag van wisselwerkende elektrone ’n sentrale rol speel. In teenstelling met die heeltallige kwantum Hall-effek is die ontstaan van ’n energie gaping in die fraksionele geval nie ’n enkeldeeltjie effek nie, maar kan uitsluitlik aan die Coulomb wisselwerking toegeskryf word. Die teoretiese raamwerk waarbinne hierdie veeldeeltjie probleem verstaan word is grootliks gebaseer op Laughlin se proefgolffunksie en die komposiete-fermion beeld van Jain. In laasgenoemde word die fraksionele kwantum Hall-effek van wisselwerkende elektrone geformuleer as die heeltallige kwantum Hall-effek van swak-wisselwerkende kwasi-deeljies wat as komposiete-fermione bekend staan. Hierdie beeld lewer ’n kwalitatiewe beskrywing van die wisselwerkende sisteem se lae-energie spektrum en lei tot ’n veralgemening van Laughlin se golffunksies vir die elektron grondtoestand. Hierdie voorspellings is deur verskeie numeriese studies geverifieer. In hierdie tesis ontwikkel ons ’n alternatiewe formulering van die komposiete-fermion beeld binne ’n strenger wiskundige raamwerk. Ons doel is om die verband tussen die sterk-wisselwerkende elektron sisteem en sy duale beskrywing in terme van swak-wisselwerkende kwasi-deeltjies op die vlak van die mikroskopiese Hamilton-operator self te realiseer. Hierdie konstruksie lei tot ’n analitiese uitdrukking vir die opwekkingsenergie wat baie goed met bestaande numeriese resultate ooreenstem. Ons identifiseer ook ’n afbeelding tussen die vrye-deeltjie en wisselwerkende toestande waarbinne die Jastrow-Slater struktuur van die komposiete-fermion proefgolffunksies op ’n natuurlike wyse na vore kom. Verder werp ons formalisme nuwe lig op kwessies binne die standaard heuristiese konstruksie, veral met betrekking tot die oorsprong van die effektiewe magneetveld en die rol van ho¨er effektiewe Landau vlakke. Ons lewer ook uitspraak oor die vraagstuk van die oorvleueling van ongeprojekteerde komposiete-fermion golffunksies met die laagste Landau vlak van die vrye-deeltjie Landau probleem.

Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1995.

The magnetosphere of pulsars is thought to consist of an electron-positron plasma rotating in the pulsar magnetic field (Beskin, Gurevich & Istomin 1983; Lominadze, Melikidze & Pataraya 1984; Gurevich & Istomin 1985). A finite, and indeed large, longitudinal electric field exists outside the star, and may accelerate particles, stripped from the surface, to high energies (Goldreich & Julian 1969; Beskin 1993). These particles may leave the magnetosphere via open magnetic field lines at the poles of the pulsar. This depletion of particles causes a vacuum gap to arise, a double layer of substantial potential difference. The primary particles, extracted from the star's surface, are accelerated in the double layer, along the pulsar magnetic field lines, and so produce curvature radiation. The curvature photons, having travelled the distance of the double layer may produce electron-positron pairs above the vacuum gap. These first-generation secondary particles, although no longer accelerating, may synchroradiate, generating photons which may then produce further electron-positron pairs. These synchrophoton produced pairs will be at energies lower than curvature photon produced pairs, since synchrophoton energies are approximately an order of magnitude less than that of the parent curvature photon. An attempt to model the electron-positron pulsar magnetosphere is made. A four component fluid electron-positron plasma is considered, consisting of a hot electron and positron species, at temperature Th , and a cool electron and positron species at temperature Tc . The hot components represent the parent first-generation curvature-born pairs, and the cooler components represent the second-generation pairs, born of synchrophotons. The hot components are assumed to be highly mobile, and are thus described by a Boltzmann density distribution. The cool components are more sluggish and are thus described as adiabatic fluids. The model is symmetric in accordance with pair production mechanisms, so that both species of hot(cool) electrons and positrons have the same temperature Th(Tc, and number density Nh(Nc ) . In the interests of completeness, linear electrostatic waves in five different types of electron-positron plasmas are considered. The dispersion relations for electrostatic waves arising in these unmagnetized plasmas are derived. Single species electron-positron plasmas are investigated, considering the constituents to be: both Boltzmann distributed; both adiabatic fluids; and finally, one species of each type. Linear electrostatic acoustic waves in multi-component electron-positron plasmas are then considered, under the four component model and a three component model (Srinivas, Popel & Shukla 1996). Small amplitude nonlinear electron-positron acoustic waves are investigated, under the four component electron-positron plasma model. Reductive perturbation techniques (Washimi & Taniuti 1966) and a derivation of the Korteweg-de Vries equation result in a zero nonlinear coefficient, and a purely dispersive governing wave equation. Higher order nonlinearity is included, leading to a modified Korteweg-de Vries equation (Watanabe 1984; Verheest 1988), which yields stationary soliton solutions with a sech dependence rather than the more familiar sech2. Arbitrary amplitude solitons are then considered via both numerical and analytical (Chatterjee & Roychoudhury 1995) analysis of the Sagdeev potential. The symmetric nature of the model leads to the existence of purely symmetrical compressive and rarefactive soliton solutions. Small and arbitrary amplitude soliton solutions are compared, and show good correlation. Under the assumption of Boltzmann distributed hot particles, severe restrictions are imposed on the existence domains of arbitrary amplitude soliton solutions. The Boltzmann assumption places a stringent upper limit on the cool species number density, in order for the solutions to be physical. An investigation is made of results obtained for an asymmetric electronpositron plasma (Pillay & Bharuthram 1992), consisting of cold electrons and positrons, and hot Boltzmann electrons and positrons at different temperatures Teh and Tph , and number density Neh and Nph . It is found that the assumption of Boltzmann particles again places restrictions on the acoustic soliton existence space, and that the results obtained may be physically invalid. Valid solutions are obtained numerically, within the boundaries of allowed cool species density values. / Thesis (M.Sc.)-University of Natal, Durban, 1998.

Plasma Source Ion Implantation (PSII) is the process of implanting high energy ions [10-50 keV] into metallic targets, by pulsing them negatively whilst immersed in a background plasma. PSII achieves surface hardening, and increased wear and corrosion resistance. Numerous papers have been published describing numerical simulations and models of the PSII process, most of which have been limited to one dimension. This thesis presents the results of work carried out III the Plasma Processing Laboratory at the University of Natal, Durban, during 1994-1995. In particular, measurements of two-dimensional plasma sheath effects due to spherical and complex shaped targets are compared with a particle-in-cell simulation code. The simulation results are used to define a relationship between the plasma potential of the sheath edge and the saturation currents. Thus allowing for the saturation currents to be used to trace sheath evolution. These results are compared with the experimental measurements from the spherical target. Results from the rectangular and complex saw-tooth targets show a lack of sheath conformality. The ion saturation currents were susceptible to electron swamping, which occured in localised regions associated with target structure. It is thought that secondary electrons ejected from the target are focused and accelerated by the high target potential into these regions, where they swamp the ion current. / Thesis (M.Sc.)-University of Natal, Durban, 1996.

A Solar Radiation Concentrating System for generation of high temperature heat for a solar oven was developed and evaluated at the University of KwaZulu-Natal, Westville Campus, Durban - South Africa. The system concentrates direct solar radiation on a small area receiver which absorbs the radiation and converts it into thermal energy that may be stored and used for several applications where food preparation and water pasteurization is the priority. The concentrator, area 2.2 m², is a half satellite communication dish covered with trapezoidal acrylic mirror tiles. The receiver/absorber is a spiral coil of blackened stainless steel pipe. Oil is circulated as heat transfer fluid. To determine the optimal dimension and position of the receiver, two experimental methods were used: (1) The tiles were scanned using a vertical, self adjusting laser beam to get a distribution of reflected radiation across the focal volume. (2) A thin, blackened stainless steel plate was placed at appropriate distances in the focal volume, and temperature distribution scanned using a temperature gun. The latter method proved to be the more useful. Results of the analysis of system performance showed that the system has the capability to produce high temperatures for domestic purposes. The efficiency of the system is about 35 %. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.

The soil being delivered with sugar cane consignments. from the cane fields to the factories, has been a recent cause for concern in the South African sugar industry. The soil impurities increase the wear of processing machinery reduce extraction efficiency and represents an unnecessary transport of material. The cost due to soil was estimated at R63 million (about US $8 million) over the 1996/97-season. The need to reduce costs, due to the unwanted soil component, has been given a high priority. Ashing is currently used by the sugar industry to estimate the amount of soil in cane. Although simple to implement, the method is destructive, requires long processing times and limited to small sample sizes. In fecent times, non-destructive techniques have become more prominent in industry. Hence, the decision to apply such techniques to the soil in cane-problem. This dissertation describes an experimental investigation into Dual-Energy Transmission (DuET) and X-ray lmaging for quantifying the amount of soil in cane. DuET can determine the relative concentrations of the components of a binary mixture by measuring the transmission of low- and high-energy gamma photons through the mixture. The principle of DuET was successfully demonstrated with aqueous solutions of ferric chloride. Experimentally-determined mass attenuation coefficients of water and ferric chloride were compared to theoretical values. DuET was then applied to dried, shredded sugar cane spiked with various amounts of soil. Results showed large variations in the predicted soil concentrations. These variations were attributed to radiation scatter and incomplete volume sampling by the radioactive source. However, new experimental arrangements are expected to improve the technique: initial test results are given of a sample holder that continuously rotates a sample up and down through the source-detector axis. An alternative approach to processmg DuET-spectra, using the discrete wavelet transform coupled with an artificial neural network, is also introduced. X-ray Imaging was the second technique investigated. A literature survey revealed that this technique had not previously been applied to the soil in cane-problem. The present work constituted an initial investigation to determine the feasibility of applying X-ray imaging to measure the amount of soil in cane. The soil/cane-samples, that were used for DuET, were imaged us ing a commercial mammography unit, and the resulting radiographs were analysed using image processing techniques. Although the results are promising, a more comprehensive investigation is foreseen. / Thesis (M.Sc.)-University of Natal, Durban, 2001.