Reversal electron attachment ionizer for detection of trace species

An in-line reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region and executing a reversal of said electrons, such that the electrons possess zero kinetic energy at the point of reversal, may be used to produce both negative and positive ions. A sample gas is introduced at the point of electron reversal for low energy electron-(sample gas) molecule attachment with high efficiency. The attachment process produces negative ions from the sample gas, which includes species present in trace (minute) amounts. These ions are extracted efficiently and directed to a mass analyzer where they may be detected and identified. The generation and detection of positive ions is accomplished in a similar fashion with minimal adjustment to potentials applied to the apparatus

A preliminary assessment of small steam Rankine and Brayton point-focusing solar modules

A preliminary assessment of three conceptual point-focusing distributed solar modules is presented. The basic power conversion units consist of small Brayton or Rankine engines individually coupled to two-axis, tracking, point-focusing solar collectors. An array of such modules can be linked together, via electric transport, to form a small power station. Each module also can be utilized on a stand-alone basis, as an individual power source

Design and performance of an aerodynamic molecular beam and beam detection system

Design and performance of aerodynamic molecular beam syste

Laser welding of titanium and tin plate

Imperial Users onl

Lightning protection of aircraft

The current knowledge concerning potential lightning effects on aircraft and the means that are available to designers and operators to protect against these effects are summarized. The increased use of nonmetallic materials in the structure of aircraft and the constant trend toward using electronic equipment to handle flight-critical control and navigation functions have served as impetus for this study

The development of a warhead into an integrated weapon system to provide an advanced battlefield capability

This thesis addresses the topic of integration of weapons systems into communication networks to provide an advanced battlefield capability, with particular application to air launched and long range crew served weapon systems which may also be vehicle mounted. It considers the use of 'Military off-the-shelf' seeker, navigation and communication systems coupled with a novel tandem warhead system. This combination of 'low risk' technologies and a novel warhead system is intended to demonstrate a greater flexibility in weapon systems which could be exploited to reduce development risk, integration risk, qualification costs and increase target defeat capability across the wider more current target set. The use of a suitable communication and navigation system enabling integration of such a weapon system into a networked force was also investigated. This thesis is based on one area of research; Multiple Effects Weapons. Research is being undertaken by several nations on Multiple Effects Weapons. The aim of this research is not to provide a one weapon fits all solution, a panacea, the aim is to widen the utility of one system which could be employed in many roles. As yet no warhead system has achieved the types of effects that are being sought, although research and product development – particularly in the United States of America - continues. Therefore the United Kingdom government has sought to understand what technologies would be required to achieve a truly flexible warhead system which would enable defeat of large Main Battle Tanks, heavily armoured Infantry Fighting Vehicles, Soft Skinned Vehicles, infantry and urban structures. To this end numerical modelling, design and a demonstration programme of a MEW warhead system was performed. MEW systems are not only reliant on 'Smart' warhead systems, the application of sensors, fuzing and communication systems are crucial to enable suitable employment of a 'one size fits most' approach. The other important sub-systems which provide the link to the battlefield network are also discussed in this thesis, the inclusion of these well developed low risk technologies make it is possible to bring such systems into service in the near term with increased system flexibility. The integration of such a system relies on the current United States Department of Defense procurement strategy which includes development of the Joint Tactical Radio System radio system which will allow Ad-Hoc networking between platforms, weapons systems and commanders. Airframe and propulsion technologies are not discussed; they are outside of the scope of this thesis. The use of proprietary data from suppliers other than QinetiQ has been avoided as suitable permissions are not in place, this has limited the systems engineering aspects of this thesis to high level block diagrams which provide guidance on integration issues

Experimental and numerical investigation of abrasive waterjet polishing technology

The objective of this investigation is the development of the abrasive waterjet (AWJ) based polishing technology. The result of the investigation will assist the implementation of AWJ polishing for manufacturing processes and procedures. Experimental exploration of AWl polishing involving processing of difficultmachine materials such as Alumina ceramic and stainless steel. Surface improvement due to this processing is evaluated by measuring the roughness of the generated surfaces and examining the microhardness and micro-topography of the surfaces using Scanning Electronic Microscopy (SEM). The surface roughness of 0.3 micron was obtained at samples of ceramic and metal alloys at a reasonable rate using 500-mesh garnet. No surface defects are induced. The effect of various process variables on the topography of surfaces generated during AWJ polishing was evaluated, It is shown that the particles dimension and jet impact angle are two critical parameters controlling the process. The former determines the feasibility of AWJ polishing, and the later limits the extent of improvement in the surface topography. The force exerted on the sample surface is measured at various impingement angles. And, the effects of the tangential and normal component of the force on the surface topography is evaluated. The abrasive particles which constitute a machining tool in the AWJ polishing are collected after mixing and after impact, and analyzed using Laser Scanning Sizer and SEM. The acquired data reveal the details of the mechanism of AWJ polishing processes. Numerical simulation of the motion of particles prior and after the impingement are conducted. Numerical solutions of the differential equations as applied to the two-phase turbulent jet flow are obtained using FIDAP package. The numerical prediction of jet velocity and force exerted on the target surface comply with the experimental results. The simulation of particles trajectories reveals existence of five distinctive patterns of particles motion which determine the surface topography. This work pioneers the use of AWJ as a polishing tool. and identifies the principal features of AWJ polishing and its use of computational packages for evaluation of the behavior of ultrahigh speed two-phase flows

Systematic study of instrumental mass discrimination in multi-collector inductively coupled plasma-mass spectrometry

Multi-collector inductively coupled plasma - mass spectrometry (MC-ICP-MS) has gained substantial importance in isotopic analysis over the last two decades. In the beginning, MC-ICP-MS was almost solely deployed in geo- and cosmochemistry and in nuclear sciences and industry. Nowadays, many other scientific fields make use of the technique, which is mostly based on the high versatility of the ICP ion source and the high sample throughput in comparison to methods with equal or even slightly better precision, such as thermal ionization mass spectrometry (TIMS). The major benefit of MC-ICP-MS is clearly the high ionization power of the ICP, compared to, e.g. that of thermal ionization. A major limitation of MC-ICP-MS is the omnipresent instrumental mass discrimination. It is the effect that light isotopes are discriminated against heavier isotopes during the measurement. The goal of this PhD research project was to identify and possibly quantify the major contributors to instrumental mass discrimination in MC-ICP-MS. Commonly, instrumental mass discrimination is attributed to space-charge effects. Even though this is an easy to comprehend effect at first glance, it becomes more complicated once studied more closely. Firstly, space-charge effects are present in charged particle beams only. Secondly, space-charge effects are most severe for low energetic particle beams with high current. Certainly, the space-charge effects are not the only contributors to mass discrimination. Several other contributors have been identified in the past, namely: collisions, sample introduction and ion formation and energy-selective ion transmission. The effect of the above mentioned processes in terms of mass discrimination were investigated by several strategies. The processes occurring during the ion beam formation were addressed by the Direct Simulation Monte Carlo method. Due to the nature of the ion source, the plasma is extracted from ambient pressure into the vacuum of the mass spectrometer; leading to drastically reduced fluid density. Yet, sufficient collisions between particles take place to possibly contribute to mass discrimination. The modeling results show a significant alteration of the fluid composition after the skimmer cone. Also a radial fractionation of the fluid was found. The ion beam is formed shortly after the plasma is extracted through the skimmer cone, the electrons are lost; a process known as charge-separation. During this phase, the space-charge effects are strongest. Thus a radial dependence of the isotopic composition of the ion beam might occur. This particular effect was investigated by two experiments, one comprising of ion implantation for the subsequent determination of the radial composition of the ion beam, the second experiment with a variable aperture addressing the shortcomings of the ion implantation and provide reliable \emph{in situ} information about the beam composition and diameter. These beam diameters are in contradiction to those expected from typically reported ion beam current. In order to measure the gross beam current, a Faraday cup was placed after the first ion lens of the mass spectrometer. The results reveal a much lower ion current than reported in literature, but are in reasonable agreement with estimations by the Child-Langmuir law for space-charge limited beams. Finally, it has to be pointed out that no dominant contributor to the mass discrimination could be identified. However, the energy-selective transmission can be excluded from the list of contributors, given the low ion beam current with the associated quasi complete beam transport. Since sample introduction a priory can be ruled out, only two contributors remain: collisions and space-charge effects. Both contributors can hardly be separated from one another experimentally, i.e., a higher throughput through the interface will lead to more collisions in the interface and consequently, to a higher ion beam current after charge-separation. Yet, the isolated treatment of both effects in computer simulations might provide a tool to solve this problem. Of course, the same simulator would need to have the capability to model both effects simultaneously, as well as separately, which is not yet possible

Numerical Simulations

This book will interest researchers, scientists, engineers and graduate students in many disciplines, who make use of mathematical modeling and computer simulation. Although it represents only a small sample of the research activity on numerical simulations, the book will certainly serve as a valuable tool for researchers interested in getting involved in this multidisciplinary field. It will be useful to encourage further experimental and theoretical researches in the above mentioned areas of numerical simulation