The vacuum system of the Van de Graaff generator is described. Techniques in the construction of the high voltage vacuum tubes are indicated. The required performance of the system and the methods of attaining it are outlined, calculations being given in the Appendices. Vacuum pressure gauges are described and the indicated performance of the system recorded. Vacuum protection circuits are discussed. Methods of leak detection are discussed and the University of British Columbia mass spectrometer leak detector described in detail. The theory of analysis by a spectrometer with a coterminous crossed electric and magnetic field is given. An operating procedure for the spectrometer is described in detail and some results recorded and discussed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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This thesis discusses the design, construction, and debugging of an experimental apparatus to measure fouling in smooth and/or augmented copper alloy condenser tubes. In addition, guidelines and recommendations are made for construction of similar devices. Specification sheets of the system components, detailed design calculations, and photographs of the apparatus are included in the appendices.

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No description available.

Previous tests of an explosion driven hydrodynamic shock tube revealed peak pressure data significantly lower than values predicted from the semiempirical scaling laws. It was hypothesized that part of the deviation was due to error in determining shock wave parameters and part might be due to measurement error caused by mechanical vibration of the tube. This investigation was conducted in two parts. In the first part, shock wave parameters were determined using a digital computer and curve fitting techniques to analyze digitized shock wave data. The second part involved determining the frequency components of the shock wave data noise content and comparing this to the dynamic characteristics of the tube which were investigated through an impulse testing technique. From these efforts higher values for the peak pressure were verified but no evidence was found that vibration of the tube caused significant degradation of shock wave test data.

In order to better simulate an explosive underwater environment, a new design of the existing explosion driven hydrodynamic conical shock tube has been proposed. This new concept calls for the removal of part of the old tube to accommodate a distributed breach plug. The distributed breach should enhance shock wave characteristics by minimizing the energy losses associated with plastic deformations which occur at detonation. This report makes use of a finite element program, SAP IV, to investigate the modal characteristics of the new distributed breach design. A dynamic response history analysis has also been performed in order to predict the response of the structure to loads characteristic of an ideal shock wave as it propagates along the tube axis. From these efforts some insight has been gained into the structural feasibility of the new design

An explosive driven, water filled, conical shock tube was designed and evaluated regarding its ability to amplify a charge weight and to produce hydrodynamic spherical shock waves. The results show that the shock waves in the tube are essentially spherical in nature--with an initial exponential shape, peak pressure attenuation as (1/R)1.13 and the time constant spreading roughly as (R).22. The charge weight was amplified by a factor of 3600 compared to a theoretical amplification of 7770. An estimate of the energy absorbed by the breach plug (which houses the charge) during an explosion was performed. The peak pressure data taken from the detonation of number 8 strength blasting caps were seen to satisfy the semiempirical scaling law. However, with the addition of plastic explosive to the blasting cap, peak pressure lower than that predicted by the scaling law was observed. At this time it is felt that a decreasing amplification factor with charge weight is the cause for the lower than predicted peak pressure. More data are needed to verify this hypothesis.

L'assemblage d'éléments en bois est majoritairement réalisé à l'aide de broches métalliques, mais certaines recherches scientifiques tentent d'orienter ces assemblages vers une conception intégrant plus de bois. L'utilisation de connecteurs en bois densifié a montré l'efficacité du processus de densification sur le matériau bois pour améliorer notamment la résistance d'assemblages de membrures en bois par rapport à une connexion par goujon en bois non densifié. Les caractéristiques mécaniques de ce nouvel assemblage sont prometteuses selon le groupe de recherche AFTB (Adhesive Free Timber Buildings) mais restent tout de même inférieures en termes de rigidité et de ductilité lorsqu'elles sont comparées à un assemblage similaire par broche métallique. Ainsi, la présente maîtrise a cherché à étudier une solution de confinement du goujon en bois densifié dans un tube d'aluminium pour améliorer les caractéristiques mécaniques évoquées. Un prototype de goujon hybride bois-aluminium a été fabriqué et testé en flexion trois-points. La comparaison avec le goujon en bois densifié a montré une nette amélioration des caractéristiques de résistance et de rigidité ainsi qu'un gain en ductilité à travers la retenue de la rupture brutale du goujon en bois densifié par l'enveloppe d'aluminium. Des essais de cisaillement double ont aussi été menés avec des connecteurs en bois densifié, hybrides et en acier pour permettre l'identification de paramètres nécessaires à la création d'un modèle numérique ayant pour objectif d'optimiser la conception du prototype hybride bois-aluminium. Celui-ci a permis d'étudier différentes conceptions hybrides et de montrer qu'avec une enveloppe de 1 mm, le goujon hybride apportait à l'assemblage une bien meilleure résistance et rigidité que le goujon en bois densifié, mais tout de même inférieure de moitié en comparaison à un goujon en acier de même diamètre. Cependant, l'amélioration du modèle est encore nécessaire pour permettre l'étude numérique des modes de ruine du goujon hybride. / The assembly of timber elements is mostly done with steel fasteners, but some scientific studies are trying to conduct these assemblies towards a design integrating more wood. The use of compressed wood dowels has shown the efficiency of the densification process on the wood material to improve the resistance of wood member connections compared to a wood dowel connection. The mechanical characteristics of this new connection are promising according to the AFTB (Adhesive Free Timber Buildings) research group but remain inferior in terms of stiffness and ductility when compared to a similar steel dowel connection. Thus, the present study investigated a solution to confine a compressed wood dowel in an aluminum tube to improve the mentioned mechanical characteristics. A prototype of hybrid wood-aluminum dowel was manufactured and tested in three points bending. The comparison with the compressed wood dowel showed a clear improvement of the strength and stiffness characteristics as well as a gain in ductility through the restraint of the brutal rupture of the compressed wood dowel by the aluminum envelope. Double shear tests were also conducted with densified wood, hybrid, and steel connectors to allow the identification of parameters necessary for the creation of a numerical model with the objective of optimizing the design of the hybrid wood-aluminum prototype. This model allowed studying different hybrid designs and to show that with a 1 mm envelope, the hybrid dowel brought to the assembly a much better resistance and rigidity than the compressed wood dowel but still less than half in comparison to a steel dowel of the same diameter. However, the improvement of the model is still necessary to allow the numerical study of the failure modes of the hybrid dowel.

As a design and analysis aid for the development of an experimental TWT, a computer program is written which allows the small-signal gain to be computed for various operating conditions, such as various conditions of tube bias (beam voltage and current) and frequency. In order to arrive at a value for the gain, a number of parameters need first to be defined or calculated. Using the method (Approach II) of Jain and Basu [17] which is applicable to a helix with a free-space gap between it and circular dielectric support rods surrounded by a metal shell, the dielectric loading factor (DLF) for the structure is found and the dispersion relation then solved to obtain the radial propagation constant y and axial propagation constant B. The method is tested for a helix with measured data and found to be acceptably accurate. Helix losses are calculated for the low-loss input and output sections of the helix, using the procedures developed by Gilmour et al [14,18], from which values are found for the helix loss parameter d. Another value for d, obviously much larger, is also found for the lossy attenuator section of the helix. Here measured data for the attenuator is used as a basis for a polynomial which models the attenuator loss as a function of frequency. The Pierce gain parameter C is found using the well-known equations of Pierce [21,22,26], and then the space-charge parameter Q. Here knowledge of the space-charge reduction factor F is required to find Q, and a simple non-iterative method is presented for its calculation, with some results. From the other parameters already calculated the velocity parameter, b, is then found. since sufficient information is now available, the electronic equations are solved. These equations are in a modified form, better accounting for the effects of space-charge than the well-known standard forms. Results are compared and slight differences found to exist in the computed gain. Now that the x's and y's (respectively the real and imaginary parts of the complex propagation constants for the slow and fast space-charge waves) are known the launching loss can be calculated. Launching losses are found for the three space-charge waves, not just for the gaining wave. The gain of the TWT is not found from the asymptotic gain equation but from a model which includes the effects of internal feedback due to reflections at the ports and attenuator. Values of reflection coefficients are modelled on the results of time-domain measurements (attenuator) and found by calculation (ports). This model permits the unstable behaviour of the tube to be predicted for various conditions of beam current and voltage and anticipates the frequencies at which instability would be likely. Results from simulations are compared with experimental observations. The need to pulse the experimental tube under controlled conditions led to the development of a high-voltage solid state pulse modulator providing regulated output pulses of up to 5000V and 200mA directly, without the use of transformers. The pulse modulator design embodies two unusual features a) its operation is bipolar, delivering positive or negative output pulses, depending only on the polarity of the rectifier input, and b) the use of multiple regulating loops and stacked pass elements to achieve high-voltage operation. Some results are presented. / Thesis (Ph.D.)-University of Natal, Durban,1994.