Turbulent liquid sheets have been proposed to protect solid structures in fusion power plants by attenuating damaging radiation. For the High-Yield Lithium-Injection Fusion Energy (HYLIFE-II) inertial fusion energy (IFE) power plant concept, arrays of molten-salt sheets form a sacrificial barrier between the fusion event and the chamber first wall while permitting target injection and ignition. Thick liquid protection can help make fusion energy commercially attractive by reducing chamber size and prolonging chamber lifetime. Establishing an experimental design database for this basic building block flow will provide valuable information about various thick liquid protection schemes and allow reactor designers to establish acceptable tolerances between chamber components. Turbulent water sheets issuing downwards into ambient air were studied experimentally at Reynolds numbers of 53,000 ??0,000 and Weber numbers of 2,900 ??,000 based on average velocity and the short dimension of the nozzle exit ( and delta). Initial conditions were quantified by the streamwise (x) and transverse (z) velocity components using laser-Doppler velocimetry just upstream of the nozzle exit. Characterization of the mean free-surface position and free-surface fluctuations, or surface ripple, and estimation of the amount of mass ejected as droplets from the free surface were quantified in the near-field (within 25 and delta of the nozzle exit). Surface ripple and mean sheet geometry were determined directly from planar laser-induced fluorescence visualizations of the free surface. The droplets due to the turbulent breakup of the jet, termed here the hydrodynamic source term, were measured using a simple collection technique to within 1 and delta of the nominal free surface of the jet. The influence of various passive flow control techniques such as removing low-momentum fluid at the free surface (boundary-layer cutting) on sheet geometry, surface ripple, and turbulent breakup were also quantified. The data obtained in this research will allow designers of inertial fusion energy systems to identify the parameter ranges necessary for successful implementation of the thick liquid wall protection system.

An experimental investigation was conducted using particle image velocimetry to study the effect of nozzle geometry on turbulent free orifice jets. The nozzle geometries studied include the round, cross, flower, star, rectangular and elliptical nozzles (aspect ratio 2). The spread rate of the rectangular nozzle was 61% greater than the square nozzle while the elliptical nozzle was 45% greater than the round nozzle using the conventional half velocity width. The superior mixing capacity of the rectangular and elliptical nozzles is attributed to the axis-switching mechanism. Evaluation of the energy budget showed a higher level of production of turbulence and convection of the mean flow for the rectangular nozzle compared with the round nozzle. Two-point auto-correlation function revealed larger structures in the non-circular nozzles and in particular the rectangular nozzle. The Kolmogorov and Taylor microscales however, did not show any significant dependency on nozzle geometry. / October 2017

Master of Science / Department of Animal Sciences and Industry / Terry A. Houser / Nursery age pigs (n=198) were used to evaluate the difference in the occurrence of injection site abscesses between needle-free jet injection and conventional needle-and-syringe injection systems. Pigs were fed for 21 d prior to treatment administration to acclimate the pigs to the environment of the Kansas State University Segregated Early Weaning (SEW) unit. On d 21 each pig was injected with aluminum hydroxide adjuvant in the neck and ham with needle-free jet injection (Pulse Needle-Free Systems, Lenexa, KS) and conventional needle-and-syringe injection. Needle-free and conventional needle-and-syringe injections were randomly assigned to pig side yielding a total of 396 injections per treatment with a total of 792 injections sites. Immediately prior to injection, the external surface of the injection sites were contaminated with an inoculum of Arcanobacterium pyogenes, a bacterium commonly associated with livestock abscesses. The pigs were then fed for a period of 27 or 28 d. On d 27 or d 28 the pigs were humanely euthanized and sent to the Kansas State Veterinary Diagnostics Laboratory where necropsies were performed and the injection sites harvested for histopathological evaluation. The needle-free jet injection system was associated with more injection site abscesses than the conventional needle-and-syringe injection method for both neck (P=0.0625) and ham (P=0.0313) injection sites. Twelve abscesses were found at injection sites administered via needle-free jet injection method while only 1 abscess was found with the conventional needle-and-syringe injection method. 5 abscesses were found at the neck injection sites and 8 abscesses were found at ham injection sites. There were no significant differences seen in tissue granulation resulting from reaction to the adjuvant. In summary, the implementation of needle-free jet injection systems in market hog production will be beneficial to eliminate needles and needle fragments in meat products but, when in the presence of Arcanobacterium pyogenes, it may increase the occurrence of injection site abscesses in pork carcasses that will need to be trimmed in pork processing plants. Although more abscesses were associated with needle-free jet injection, their occurrence was observed at a very low rate given that all injection sites were intentionally contaminated prior to injection.

A eficiência de motores a combustão está diretamente relacionada a mistura dos reagentes. O que é muito desejado em todos os sistemas, inclusive em sistemas aeroespaciais onde a combustão ocorre de forma contínua como nos motores a jato, motores de foguete, ramjet e scramjet. No caso do scramjet a combustão ocorre em regime supersônico e conhecer como os dois fluidos se misturam na câmera de combustão é muito importante pois o tempo de residência na câmera é muito reduzido, aumentando a importância de uma mistura homogênea para a eficiência da combustão. Em determinados casos pequenas pertubações em um jato vão se amplificar podendo ocasionar a transição do escoamento laminar para turbulento. O que é desejado visto que escoamentos turbulentos são caracterizados pela grande capacidade de mistura. No presente trabalho estudamos a estabilidade de jatos coaxiais composto por dois fluídos com pequenas pertubações na base para escoamentos supersônicos para casos bidimensionais e tridimensionais. O escoamento foi investigado utilizando simulação numérica e a teoria de estabilidade linear, os resultados de ambos os métodos foram comparados, casos com pertubações bidimencionais e tridimencionais foram analizados. As simulações numéricas foram realizadas utilizando diferenças finitas de alta ordem de precisão para a discretização espacial. A integração temporal foi feita utilizando o método de Runge-Kutta de quarta ordem. Os resultados de ambos os métodos mostraram uma boa concordância. / The efficiency of combustion engines are strict related to the mixing between reagents. That is very desire in every aerospace propulsion system, when the combustion is continuous such as rocket engines, ramjets and scramjets. The combustion in scramjet occurs in supersonic speed ith a very small resilience time, know how two fluids are mixed in this case is very important because are direct related to the efficiency of the combustion. In such cases small disturbances in a jet flow can be amplified until occur the transition from a laminar flow to a turbulent flow, that is desired because the great capacity of mixing of turbulent flows. In this work are studied the jet flow stability when the jet are composed by two fluids with small disturbances in the base for supersonic flows in bidimensional and tridimensional cases. The numerical results are obtained by numerical simulation and linear stability theory (LST). High order finite difference schemes are adopted for spatial derivatives. The integration in time are caried out by a fouth order Runge-Kutta scheme. The results obtained by numerical simulation and linear stability theory show good agreement.

abstract: Conventional fluid dynamics models such as the Navier-Stokes equations are derived for prediction of fluid motion at or near equilibrium, classic examples being the motion of fluids for which inter-molecular collisions are dominant. Flows at equilibrium permit simplifications such as the introduction of viscosity and also lead to solutions that are single-valued. However, many other regimes of interest include "fluids"' far from equilibrium; for example, rarefied gases or particle-laden flows in which the dispersed phase can be comprised of granular solids, droplets, or bubbles. Particle motion in these flows is not typically dominated by collisions and may exhibit significant memory effects; therefore, is often poorly described using continuum, field-based (Eulerian) approaches. Non-equilibrium flows generally lack a straightforward counterpart to viscosity and their multi-valued solutions cannot be represented by most Eulerian methods. This strongly motivates different strategies to address current shortcomings and the novel approach adopted in this work is based on the Conditional Quadrature Method of Moments (CQMOM). In CQMOM, moment equations are derived from the Boltzmann equation using a quadrature approximation of the velocity probability density function (PDF). CQMOM circumvents the drawbacks of current methods and leads to multivariate and multidimensional solutions in an Eulerian frame of reference. In the present work, the discretized PDF is resolved using an adaptive two-point quadrature in three-dimensional velocity space. The method is applied to computation of a series of non-equilibrium flows, ranging from simple two-dimensional test cases to fully-turbulent three-dimensional wall-bounded particle-laden flows. The primary contribution of the present effort is on development, application, and assessment of CQMOM for predicting the key features of dilute particle-laden flows. Statistical descriptors such as mean concentration and mean velocity are in good agreement with previous results, for both collision-less and collisional flows at varying particle Stokes numbers. Turbulent statistics and measures of local accumulation agree less favorably with prior results and identify areas for improvement in the modeling strategy. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2015

Regions containing gradients of vertical flow are often associated with sharp changes in hydrographic and biochemical water properties in coastal marine ecosystems. Often these are sites of dense plankton aggregations of critical ecological importance. In this study, a recirculating flume apparatus with a laminar, planar free jet (the Bickley jet) was used to create finescale gradients of fluid velocity (shear) in both upwelling and downwelling configurations for zooplankton behavioral assays. Particle image velocimetry (PIV) was used to fully resolve the velocity fields allowing us to fine-tune experimental parameters to match fluid mechanical conditions commonly measured in the field. Zooplankton behavioral assays with two tropical calanoid copepods, Acartia negligens and Clausocalanus furcatus, an estuarine mysid, Neomysis americana, and the larvae of an estuarine mud crab, Panopeus herbstii, were conducted in control (stagnant), upwelling, and downwelling flow configurations. Statistical analyses (ANOVA) of individual zooplankton trajectories revealed the potential for individual behavioral responses to persistent finescale vertical shear layers to produce population scale aggregations, which is proposed here as a mechanism of patchiness in coastal marine ecosystems. Results from behavioral analyses reveal species-specific threshold shear strain rates that trigger individual behavioral responses. Furthermore, results show statistically significant changes in behavior (relative swimming speed, turn frequency, heading) for all species tested in response to a coherent shear structure in the form of finescale upwelling and downwelling jets. The results show that changes in individual behavior can increase Proportional Residence Time (PRT = percent time spent in the jet structure). On a population scale, the increase in PRT can lead to dense aggregations around persistent flow features, which is consistent with numerous field studies. These dense, patchy aggregations of zooplankton have profound trickle-up ecological consequences in coastal marine ecosystems.

The basis of mixing ventilation is the airflow supply to the room by means of jets initiatedfrom the ventilation diffusers. To avoid the draught problem, the design of mixing ventilationmakes uses the throw term, which is defined as the distance to the supply air terminal inwhich the jet centreline mean velocity is decreased to a given value. Traditionally, the throw ismeasured by the supply air device manufacturer. The throw is applied by designers to estimatethe velocity levels in the occupied zone. A standard for determining the throw is the CENstandard CEN/TC156/WG4 N86 "Draft Standard. Air terminal Devices. AerodynamicsTesting And Rating For Mixed Flow Application".The measurement of the throw is very time consuming even with the free jets and theinfluence of the room (the effect of confinement) is not considered. The objective of thepresent study is to give a basis for modifying the existing design and testing method used topredict the velocities in the occupied zone during the design process. A new method whichmay probably be more easier than the existing methods and at the same time give a betterprecision by including the confinement effect.In this thesis two methodological systems of experiment and numerical simulations have beenused. The numerical predictions are used in comparison with the measurements. Thereasonable agreement of the above mentioned methods is implemented to numerical study ofthe other room configurations which are not experimentally studied. This examining methodallows the possibility of studying a lot of configurations and in this manner generalising of theresults. Although the experimental part was made for both model-scale and full-scale testrooms, a large amount of data was obtained for a new test room whose dimension aresystematically varied. All of studies have been made for the isothermal case and themeasurements of velocities and pressures conducted along the room perimeters. The effect ofshort and deep rooms on the properties of the jet ( velocities, pressure, integral scale, jetmomentum, the rate of spreading of jet and turbulence intensities) have been carried out.Some old and recent investigations have been examined. Specially the concept of correlationsfrom open to closed rooms is criticised. It is also shown that the flow field in a confined roomis affected by many other factors than the Reynolds number. The surface pressure on theperimeters was used to calculate the reaction forces at the corners which causes recirculatingbubbles at corners. A study of the turbulent axisymmetric jet which is the basic element inturbulent shear flows and some restrictions of the traditional measurement techniques at theregion of interest in ventilation applications are discussed. The jet momentum is measured byweighing on a balance. Also a study of jets which collide with a wall , that is impinging jet,the effect of walls and confinement on the jet momentum have experimentally andnumerically been carried out. A new momentum balance model was developed for both thefree jet and confined one. An empirical relation has been found for estimation of the room’srotation centre which is used for validation of CFD results.Finally, it is found that the jets in a ventilated room which are a combination of free jet, walljet and impinging jet differ from the traditional wall jets. The rate of spreading of the jet andthe maximum velocity decay in a ventilated room are also different depending on the roomsize and its confinement.

Foram feitas simulações de um jato plano livre e incompressível usando o modelo de uma equação Spalart-Allmaras padrão e um modelo Spalart-Allmaras modificado através da alteração da escala de comprimento turbulenta. Sabe-se da literatura que no caso de jatos livres o modelo Spalart-Allmaras não consegue predizer adequadamente os resultados observados experimentalmente. Os resultados das simulações foram comparados com experimentos da literatura através de perfis de velocidade e da taxa de expansão do jato. Como esperado, os resultados obtidos das simulações utilizando o modelo Spalart-Allmaras padrão foram considerados insatisfatórios, porém o modelo Spalart-Allmaras modificado teve uma melhor concordância com os resultados experimentais. Além disso, o modelo Spalart-Allmaras modificado foi usado para simular os casos do escoamento sobre uma placa plana sem gradiente de pressão e o escoamento em um degrau com separação e gradiente adverso de pressão. Quando comparados com resultados experimentais da literatura e com resultados obtidos usando o modelo padrão, os resultados do modelo modificado obtidos para ambos os casos foram muito satisfatórios, concluindo-se que a modificação da escala de comprimento permite obter uma maior generalidade para o modelo Spalart-Allmaras. / Simulations of a plane and incompressible free jet using the standard Spalart-Allmaras model and a Spalart-Allmaras model modified by changing the turbulent length scale were carried out. It is known from literature that, in the case of the free jet, the Spalart-Allmaras model fails to adequately predict the experimentally observed results. The results of our simulations were compared with published experiments using the velocity profiles and the jet spreading rate. As expected, the results of simulations using the standard Spalart-Allmaras model were considered unsatisfactory while the modified Spalart-Allmaras model had a better agreement with the experimental results. Furthermore, the modified Spalart-Allmaras model was used to simulate the cases of flow over a flat plate with no pressure gradient and flow through a backward facing step with separation and adverse pressure gradient. When compared with experimental results from the literature and with results obtained using the standard model, the results of the modified model for both cases were very satisfactory, allowing the conclusion that the change in the length scale provided a greater generality for the Spalart-Allmaras model.

Στην παρούσα εργασία παρουσιάζονται πειραματικά αποτελέσματα των τρισδιάστατων διανυσμάτων των τυρβωδών πεδίων ταχύτητας και στροβιλότητας στην εγγύς περιοχή της τυρβώδους ορθογωνικής δέσμης με λόγο σύγκλισης 6. Οι τυρβώδεις ορθογωνικές ελεύθερες δέσμες έχουν πρακτικό ενδιαφέρον για την καύση, την πρόωση και τις περιβαλλοντικές ροές. Για την μέτρηση των μέσων και στατιστικών χαρακτηριστικών των συνιστωσών των δυο πεδίων σε διαφορετικές θέσεις στην εγγύς περιοχή της δέσμης χρησιμοποιήθηκε κεφαλή 12-αισθητήρων θερμού νήματος αποτελούμενη από τρεις κεφαλές 4 αισθητήρων. Η κεφαλή 12-αισθητήρων μετράει ταυτόχρονα τις τρεις συνιστώσες της ταχύτητας σε τρεις διαφορετικές θέσεις και επιτρέπει τον υπολογισμό των χωρικών παραγώγων του ανύσματος της ταχύτητας με την μέθοδο των πεπερασμένων διαφορών με ακρίβεια πρώτης τάξεως. Η κατασκευή της κεφαλής 12-αισθητήρων και η τεχνική μέτρηση βασίζεται στην εργασία των Lemonis & Drakos (1995) και Lemonis (1995) και έχει περαιτέρω βελτιωθεί στο Εργαστήριο Τεχνικής Θερμοδυναμικής του Πανεπιστημίου Πατρών. Οι μετρήσεις διεξήχθησαν σε αριθμό Reynolds, ReD = 21000 σε αποστάσεις κατά μήκος της ροής ίσες προς x/D =1, 3, 6 και 11, όπου D είναι το πλάτος του ακροφυσίου. Η αξιοπιστία της κεφαλής 12-αισθητήρων εκτιμήθηκε σε σύγκριση με τα αποτελέσματα της κεφαλής αισθητήρων X. Τα αποτελέσματα από τις μετρήσεις του πεδίου ταχύτητας και με τις δύο κεφαλές είναι σε καλή συμφωνία, εκτός από τις θέσεις όπου οι μεγάλες χωρικές κλίσεις της ταχύτητας και η τρισδιαστατότητα του πεδίου ταχύτητας υπονομεύουν τις μετρήσεις με την κεφαλή αισθητήρων Χ. Οι στατιστικές ιδιότητες των πεδίων της ταχύτητας και στροβιλότητας που υπολογίστηκαν από τις μετρήσεις με την κεφαλή 12-αισθητήρων εκτιμιούνται σε σύγκριση με πειραματικά και υπολογιστικά αποτελέσματα άλλων ερευνητών. Οι κατανομές των κυμαινόμενων πεδίων της ταχύτητας και στροβιλότητας δείχνουν ότι στην περιοχή του πυρήνα δυναμικού οι τιμές είναι αρκετά χαμηλές στον κεντρικό άξονα της δέσμης και αρκετά υψηλές στα διατμητικά στρώματα. Κατάντι της ροής οι διακυμάνσεις της ταχύτητας και στροβιλότητας μεταφέρονται από τα διατμητικά στρώματα προς το κέντρο και τις άκρες της δέσμης και οδηγούν στη συγχώνευση των διατμητικών στρωμάτων. Τα αποτελέσματα επιβεβαιώνουν επίσης τα υψηλά επίπεδα του ρυθμού εκφυλισμού (dissipation rate) στα διατμητικά στρώματα. Το ισοζύγιο της τυρβώδους ενέργειας παρουσιάζει σημαντικές διαφορές με το αντίστοιχο της επίπεδης δέσμης. Η σύγκριση των όρων της εξίσωσης της μέσης τετραγωνικής διακύμανσης της στροβιλότητας στη θέση x/D=11 δείχνει ότι η περιστροφή και η διάταση λόγω των διακυμάνσεων του ρυθμού παραμόρφωσης (strain rate) εξισορροπείται από τον ιξώδη εκφυλισμό της στροβιλότητας. Οι ανισοτροπίες στην εγγύς περιοχή της τυρβώδους ορθογωνικής δέσμης ερευνώνται και συζητούνται λεπτομερώς. Για την ερευνά της δομικής εξέλιξης της τυρβώδης ορθγωνικής δέσμης στην εγγύς περιοχή χρησιμοποιήθηκε επίσης και η μέθοδος PIV. Οι μετρήσεις με την μέθοδο PIV προσφέρουν το πλεονέκτημα της απεικόνισης της ροής μαζί με τη δυνατότητα καλύτερης κατανόησης των φαινόμενων της ροής, και ειδικότερα, πώς η δημιουργία, η αλληλεπίδραση και η συγχώνευση των στροβίλων συμβάλλουν στην ανάπτυξη της ορθογωνικής δέσμης. Τα αποτελέσματα των κατανομών φασμάτων ισχύος δείχνουν ότι μετά το τέλος του πυρήνα δυναμικού η ενισχυμένη συχνότητα αντιστοιχεί σε αριθμό Strouhal St=f•yc/U0≈0,11. Οι κατανομές της πυκνότητας ελικότητας στις περιοχές των διατμητικών στρωμάτων για x/D=3, 6, 11 δείχνουν μια τάση των ολικών διανυσμάτων της ταχύτητας και στροβιλότητας να ευθυγραμμιστούν. Από την άλλη, στις περιοχές των διατμητικών στρωμάτων για x/D=1 όπου το ολικό διάνυσμα της ταχύτητας είναι περίπου κάθετο προς την μέση ροή οι κατανομές παρουσιάζουν αντίθετη μορφή, όπως θα αναμενόταν. Η συλλογή πληροφοριών στην παρούσα έρευνα και η σύγκριση με τα ήδη υπάρχοντα στην βιβλιογραφία πειραματικά αποτελέσματα για τις τυρβώδες δέσμες αναμένεται να διευρύνουν περαιτέρω τη γνώση σχετικά με τη δομή των ελεύθερων διατμητικών ροών. / In the present work the three-dimensional velocity and vorticity vector fields in the near field of the rectangular turbulent jet with aspect ratio 6 have been experimentally investigated. Turbulent rectangular jets are prototypical free shear flows of practical interest in propulsion, combustion and environmental flows. The presented data, consisting of distributions of mean and statistical characteristics of the components of the two fields at several locations within the jet’s near field region, were obtained by using an in-house constructed 12-sensor hot wire probe consisting of three closely separated orthogonal 4-hot wire velocity arrays. The probe measures the three components of velocity simultaneously at three closely spaced locations. Spatial velocity derivatives are estimated using a forward difference scheme of first order accuracy. Streamwise velocity derivatives are estimated using Taylor’s frozen turbulence hypothesis. The 12-sensor construction and measurement technique relies upon previous work of Lemonis & Dracos (1995) and Lemonis (1995) and has been further improved and refined at the Laboratory of Applied Thermodynamics of the University of Patras. Measurements have been conducted in a jet with Reynolds number ReD = 21000 at nozzle distances, x/D =1, 3, 6 and 11, where D is the width of the nozzle. The performance of the 12-sensor probe is investigated in comparison with X-sensor probe measurements. Results referring to measurements of velocity with both sensors are in good agreement, except in locations where the steep velocity gradients and the three dimensionality of the velocity field undermine X-wire probe measurements. The statistical properties of the velocity-vorticity fields based on measurements with the 12-sensor probe are presented in comparison with several experimental and direct numerical simulation data of other researchers. Distributions of fluctuating velocity –vorticity fields show that in the potential core region the values are low on the centerline of the jet and quite high in the shear layers. Downstream the velocity-vorticity fluctuations spread from the shear layer towards the centre and the edge of the jet leading to merging of the two mixing layers. The results also confirm the high levels of dissipation rate in the shear layers. The turbulent energy balance shows important differences to that in plane jets. The budget of the transport equation for fluctuating enstrophy at x/D=11 indicates that the rotation and stretching by the fluctuating strain rate is balanced by the viscous dissipation of vorticity. The anisotropies in the near field of the turbulent rectangular jet are illustrated and discussed in detail. The structure development of a rectangular turbulent jet in the near field region has been also investigated experimentally using PIV. The results obtained with PIV measurements offer the advantages of flow visualization along with the possibility of better understanding the flow phenomena, in particular, how the formation, interaction and merging of vortices contribute to the development of the rectangular jet. The results of spectra distributions indicate that the most amplified frequency after the end of the potential core give rise to a Strouhal Number St=f•yc/U0≈0,11. In the regions of turbulent shear layers at x/D=3, 6, 11 the pdf’s of the relative helicity density h have shapes showing a preferred tendency for the total velocity and vorticity vectors to be aligned. On the other hand, in the regions of turbulent shear layers at x/D=1 where the total vorticity vector is more nearly orthogonal to the mean flow, the pdf’s show the opposite shape, as would be expected. Comparison and integration of the obtained information with the existing body of experimental evidence on turbulent rectangular jets is expected to enhance knowledge on the turbulence structure in free shear flows.

Research Doctorate - Doctor of Philosophy (PhD) / Helium has the highest ionization energy of any species and is as a consequence difficult to detect by conventional means. On the other hand, it is the ideal surface probe, having no net charge or spin, a low mass and a short de Broglie wavelength. Therefore, there exists a strong incentive to develop a microscopy technique based on helium atom scattering. The purpose of this thesis is to investigate in detail how an efficient helium detector might be developed using the phenomenon of field ionization, an ionization method that relies on quantum mechanical tunneling rather than the more conventional electron impact ionization techniques. In particular, the work focusses on the potential use of a novel nanomaterial, carbon nanotubes, as the source of the high electric fields required for field ionization detection. In Chapter 1 we review the history of field ionization research and the properties and synthesis methods for carbon nanotubes. Chapter 2 describes the experimental apparatus and procedures used for the present research, and Chapter 3 introduces the theoretical framework and background for field ionization. In Chapter 4, the prototypical field ionization system is considered from a detector viewpoint. The work demonstrates that existing theory is not sufficiently quantitative for describing a field ionization detector and therefore a semi-empirical theory is advanced for that purpose. Chapter 5 considers the problem of nanotube field enhancement in detail using computational methods, leading to a complete description of the maximum field enhancement of a nanotube array based on the four fundamental array parameters. Efforts to synthesize carbon nanotubes in the Newcastle plasma-enhanced chemical vapor deposition system are described in Chapter 6. Several procedures are developed for reproducible growth of nanotube films and the chemical vapor deposition system is characterized with single parameter studies. Chapter 7 presents the results of electron field emission and helium field ionization experiments carried out using the grown nanotube films. We demonstrate for the first time the field ionization of helium using a planar film of carbon nanotubes. Finally, we conclude the investigation of field ionization detection in Chapter 8 with a discussion on how such a detection method integrates into a helium microscope and in particular we detail the design and initial calculations for the planned Newcastle helium microscope.