MEG Upgrade Proposal

We propose the continuation of the MEG experiment to search for the charged lepton flavour violating decay (cLFV) \mu \to e \gamma, based on an upgrade of the experiment, which aims for a sensitivity enhancement of one order of magnitude compared to the final MEG result, down to the $6 \times 10^{-14}$ level. The key features of this new MEG upgrade are an increased rate capability of all detectors to enable running at the intensity frontier and improved energy, angular and timing resolutions, for both the positron and photon arms of the detector. On the positron-side a new low-mass, single volume, high granularity tracker is envisaged, in combination with a new highly segmented, fast timing counter array, to track positron from a thinner stopping target. The photon-arm, with the largest liquid xenon (LXe) detector in the world, totalling 900 l, will also be improved by increasing the granularity at the incident face, by replacing the current photomultiplier tubes (PMTs) with a larger number of smaller photosensors and optimizing the photosensor layout also on the lateral faces. A new DAQ scheme involving the implementation of a new combined readout board capable of integrating the diverse functions of digitization, trigger capability and splitter functionality into one condensed unit, is also under development. We describe here the status of the MEG experiment, the scientific merits of the upgrade and the experimental methods we plan to use.Comment: A. M. Baldini and T. Mori Spokespersons. Research proposal submitted to the Paul Scherrer Institute Research Committee for Particle Physics at the Ring Cyclotron. 131 Page

CFD simulation and optimisation of a low energy ventilation and cooling system

Mechanical Heating Ventilation and Air-Conditioning (HVAC) systems account for 60% of the total energy consumption of buildings. As a sector, buildings contributes about 40% of the total global energy demand. By using passive technology coupled with natural ventilation from wind towers, significant amounts of energy can be saved, reducing the emissions of greenhouse gases. In this study, the development of Computational Fluid Dynamics (CFD) analysis in aiding the development of wind towers was explored. Initial concepts of simple wind tower mechanics to detailed design of wind towers which integrate modifications specifically to improve the efficiency of wind towers were detailed. From this, using CFD analysis, heat transfer devices were integrated into a wind tower to provide cooling for incoming air, thus negating the reliance on mechanical HVAC systems. A commercial CFD code Fluent was used in this study to simulate the airflow inside the wind tower model with the heat transfer devices. Scaled wind tunnel testing was used to validate the computational model. The airflow supply velocity was measured and compared with the numerical results and good correlation was observed. Additionally, the spacing between the heat transfer devices was varied to optimise the performance. The technology presented here is subject to a patent application (PCT/GB2014/052263)

Ultra-low-cost broad-band near-infrared silicon photodetectors based on hot electrons

Cataloged from PDF version of article.Silicon is at the heart of all of the end-user digital devices such as smart phones, laptops, and wearable technologies. It is the holy grail for the largescale production of semiconductor devices since start of the semiconductor era due to its relatively good electrical, mechanical and chemical properties. Silicon’s mediocre optical properties also make it an acceptable material for energy harvesting and ultraviolet photodetection applications. But its relatively large bandgap (1.12 eV ) makes it infrared blind. So Silicon photodetectors fail to detect infrared light using traditional techniques. Hence, an all-Silicon solution is of interest for low-cost civil applications like telecommunication and imaging. Silicon based Schottky junction is a promising candidate for infrared photodetection. Internal photoemission is the main mechanism of photodetection in the Schottky junctions. Incident photons elevate the kinetic energy of the electrons in the metal so that the energetic electrons can jump over the Schottky barrier or tunnel through it. Carefully designed metal contact of the Schottky junction can, at the same time, give rise to hot electron generation through plasmon resonances. Here we introduce ultra-low-cost broad-band near-infrared Silicon photodetectors with a study over types of metal and nanostructures and fabrication techniques. The devices exhibit photoresponsivity as high as 2 mA/W and 600 µA/W at 1300 nm and 1550 nm wavelengths, and can see beyond 2000 nm wavelengths. Their dark current density is as low as 50 pA/µm2 . Simplicity and scalability of fabrication in this type of structures make them the most cost effective infrared detectors due to lack of expensive fabrication steps such as sub-micron lithography and high temperature epitaxial growth techniques.Nazirzadeh, Mohammad AminM.S

Combining Experimental and DFT Investigation of the Mechanism Involved in Thermal Etching of Titanium Nitride Using Alternate Exposures of NbF5 and CCl4, or CCl4 Only

Thermally activated chemical vapor-phase etching of titanium nitride (TiN) is studied by utilizing either alternate exposures of niobium pentafluoride (NbF5) and carbon tetrachloride (CCl4) or by using CCl4 alone. Nitrogen (N-2) gas purge steps are carried out in between every reactant exposure. Titanium nitride is etched in a non-self-limiting way by NbF5-CCl4 based binary chemistry or by CCl4 at temperatures between 370 and 460 degrees C. Spectroscopic ellipsometry and a weight balance are used to calculate the etch per cycle. For the binary chemistry, an etch per cycle of approximate to 0.8 angstrom is obtained for 0.5 and 3 s long exposures of NbF5 and CCl4, respectively at 460 degrees C. On the contrary, under the same conditions, the etch process with CCl4 alone gives an etch per cycle of about 0.5 angstrom. In the CCl4-only etch process, the thickness of TiN films removed at 460 degrees C varies linearly with the number of etch cycles. Furthermore, CCl4 alone is able to etch TiN selectively over other materials such as Al2O3, SiO2, and Si3N4. X-ray photoelectron spectroscopy and bright field transmission electron microscopy are used for studying the post-etch surfaces. To understand possible reaction products and energetics, first-principles calculations are carried out with density functional theory. From thermochemical analysis of possible reaction models, it is found that NbF5 alone cannot etch TiN while CCl4 alone can etch it at high temperatures. The predicted byproducts of the reaction between the CCl4 gas molecules and TiN surface are TiCl3 and ClCN. Similarly, TiF4, NbFCl3, and ClCN are predicted to be the likely products when TiN is exposed to both NbF5 and CCl4. A more favorable etch reaction is predicted when TiN is exposed to both NbF5 and CCl4 (Delta G = -2.7 eV at 640 K) as compared to exposure to CCl4 only (Delta G = -2 eV at 640 K) process. This indicates that an enhanced etch rate is possible when TiN is exposed alternately to both NbF5 and CCl4, which is in close agreement with the experimental results.Peer reviewe

Molecular Dynamics Simulation Of Polymer Nanocomposites In Extreme Environments

In this dissertation, lower length scale phenomena associated with the responses of hybrid materials to harsh and extreme environments were studied. The goal of this research was to reveal the underlying mechanisms of damage mitigation in these materials and the role that interface, and relevant material component interactions play in the overall material response. First, the thermal decomposition behavior of a technologically important material system, i.e., pristine graphene (PG) and graphene oxide (GO) reinforced poly(ethylene oxide) (PEO), was investigated using a reactive molecular dynamics simulation methodology. The simulations were performed in both non-isothermal (dynamic gravimetric) and isothermal modes of decomposition. Overall, the introduction of PG to the PEO system improves the thermal stability of the polymer in both decomposition modes. A delay in the temperature of the onset of decomposition in the non-isothermal mode and a nearly 60% increase in the activation energy of decomposition in the isothermal mode is observed for the PEO-PG system. This effect gets more pronounced with an increase in the PG concentration in the system. In contrast, introducing GO in the PEO system deteriorates the thermal stability of the polymer, even though, similar to the PG concentration effect, the thermal stability of the polymer is increased with increasing GO concentration. Second, the effect of surface modification of polyoctahedral silsesquioxane (POSS) and its concentration in a polyimide (PI) matrix, as well as the effect of nanoparticle type (POSS, graphene, and carbon nanotube (CNT)) and the nanoparticle orientation in Gr and CNT nanoparticles in the PI matrix exposed to atomic oxygen (AO) bombardment were studied using a reactive molecular dynamics simulation methodology. Among all systems, PI with randomly oriented CNTs or Gr nanoparticles gave, in general, the lowest mass loss, erosion yield, surface damage, AO penetration depth, and temperature. Grafting of the POSS nanoparticles with PI and the increasing the PI concentration lowers the erosion yield of the PI-POSS systems, with the effect of former being greater on the AO damage mitigation. The results of this fundamental study shed light on the lower length scale phenomena associated with AO damage mitigation in different PI-nanoparticle systems. Third, the through-thickness temperature distribution and thermal conductivities of unprotected neat crosslinked epoxy, and protected epoxy/graphene, and epoxy/montmorillonite/graphene systems were investigated against lightning strike damage. It was inferred that the montmorillonite/graphene top coating has great potential to be used as a lightning strike damage protection measure for epoxy-based composite systems. A more thorough multi-physics (electrothermal) analysis of the montmorillonite/graphene system may further reveal its lightning strike damage mitigation efficiency

Evaluation of remain well clear and collision avoidance for drones

One of the cornerstones that should enable inserting unmanned aircraft into the airspace is the development of Detect and Avoid (DAA) systems. DAA systems will improve the Remote Pilot (RP) situational awareness by means of electronic conspicuity devices, providing them with the necessary means to Remain Well Clear (RWC) from other traffic and, if necessary, avoid Mid-Air collisions (MAC). DAA systems will compensate for the loss of a pilot on board, which drastically reduces the capacity to keep a safe separation from traffic, making current Rules of the Air very challenging to achieve. Given the growing popularity of drone operations for commercial and recreational purposes, new standards should include them in the not-too-distant future. Since current DAA standards and algorithms (DO-365 and ED-258) are being developed targeting large, mostly military Remotely Piloted Aircraft Systems (RPAS), this project proposes a new set of detection volumes and alert thresholds for U-Space users according to an aircraft type classification. This will allow adapting the existing DAA algorithms to small drones, complying with the new European framework of services and applications for drones (U-Space). Because testing new safety nets (such as new DAA algorithms) on real aircraft would be dangerous and inadequate, radar reports and computer-based simulations allow for a risk-free and faster evaluation of safety net performances. Due to the current lack of real drone radar tracks, this project has developed a multi-rotor drone encounter generator tool (called DEG). This software is able to generate a large number of synthetic pairwise quadcopter drone conflict tracks, simulating the instant prior to a MAC. The way trajectories are generated by DEG strongly depends on the type of operation being flown (inspection/surveillance flights and logistic flights) and the aircraft type (including a DJI F450 and a faster version called DJI F450 FAST). The results of this project include a drone conflict trajectory example generated with DEG and an investigation of the performance and effectiveness of the DEG tool using a tailored existing DAA algorithm (DAIDALUS).Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructur

Development of a low-cost graphene-based impedance biosensor

PhD ThesisThe current applicability and accuracy of point-of-care devices is limited, with the need of future technologies to simultaneously target multiple analytes in complex human samples. Graphene’s discovery has provided a valuable opportunity towards the development of high performance biosensors. The quality and surface properties of graphene devices are critical for biosensing applications with a preferred low contact resistance interface between metal and graphene. However, each graphene production method currently results in inconsistent properties, quality and defects thus limiting its application towards mass production. Also, post-production processing, patterning and conventional lithography-based contact deposition negatively impact graphene properties due to chemical contamination. The work of this thesis focuses on the development of fully-functional, label-free graphene-based biosensors and a proof-of-concept was established for the detection of prostate specific antigen (PSA) in aqueous solution using graphene platforms. Extensive work was carried out to characterize different graphene family nanomaterials in order to understand their potential for biosensing applications. Two graphene materials, obtained via a laser reduction process, were selected for further investigations: reduced graphene oxide (rGO) and laser induced graphene from polyimide (LIG). Electrically conductive, porous and chemically active to an extent, these materials offer the advantage of simultaneous production and patterning as capacitive biosensing structures, i.e. interdigitated electrode arrays (IDE). Aiming to enhance the sensitivity of these biosensors, a novel, radio-frequency (RF) detection method was investigated and compared with conventional electrochemical impedance spectroscopy (EIS) on a well-known biocompatible material: gold (standard). It was shown that the RF detection methods require careful design and testing setup, with conventional EIS performing better in the given conditions. The method was further used on rGO and LIG IDE devices for the electrochemical impedance detection of PSA to assess the feasibility of the graphene based materials as biosensors. The graphene-based materials were successfully functionalized via the available carboxylic groups, using the EDC-NHS chemistry. Despite the difficulty of producing reproducible graphene-based electrodes, highly required for biosensor development, extensive testing was carried out to understand their feasibility. The calibration curves obtained via successive PSA addition showed a moderate-to-high ii sensitivity of both rGO and LIG IDE. However, further adsorption and drift testing underlined some major limitations in the case of LIG, due to its complex morphology and large porosity. To enable low contact resistance to these biosensors, the electroless nickel coating process is shown to be compatible with various graphene-based materials. This was demonstrated by tuning the chemical nickel bath and method conditions for pristine graphene and rGO for nickel contacts deposition

RTJ-303: Variable geometry, oblique wing supersonic aircraft

This document is a preliminary design of a High Speed Civil Transport (HSCT) named the RTJ-303. It is a 300 passenger, Mach 1.6 transport with a range of 5000 nautical miles. It features four mixed-flow turbofan engines, variable geometry oblique wing, with conventional tail-aft control surfaces. The preliminary cost analysis for a production of 300 aircraft shows that flyaway cost would be 183 million dollars (1992) per aircraft. The aircraft uses standard jet fuel and requires no special materials to handle aerodynamic heating in flight because the stagnation temperatures are approximately 130 degrees Fahrenheit in the supersonic cruise condition. It should be stressed that this aircraft could be built with today's technology and does not rely on vague and uncertain assumptions of technology advances. Included in this report are sections discussing the details of the preliminary design sequence including the mission to be performed, operational and performance constraints, the aircraft configuration and the tradeoffs of the final choice, wing design, a detailed fuselage design, empennage design, sizing of tail geometry, and selection of control surfaces, a discussion on propulsion system/inlet choice and their position on the aircraft, landing gear design including a look at tire selection, tip-over criterion, pavement loading, and retraction kinematics, structures design including load determination, and materials selection, aircraft performance, a look at stability and handling qualities, systems layout including location of key components, operations requirements maintenance characteristics, a preliminary cost analysis, and conclusions made regarding the design, and recommendations for further study

Advances in Piezoelectric Transducers

The piezoelectric transducer converts electric signals into mechanical vibrations or vice versa by utilizing the morphological change of a crystal which occurs on voltage application, or conversely by monitoring the voltage generated by a pressure applied on a crystal. This book reports on the state of the art research and development findings on this very broad matter through original and innovative research studies exhibiting various investigation directions. The present book is a result of contributions of experts from international scientific community working in different aspects of piezoelectric transducers. The text is addressed not only to researchers, but also to professional engineers, students and other experts in a variety of disciplines, both academic and industrial seeking to gain a better understanding of what has been done in the field recently, and what kind of open problems are in this area