Advances in optical surface figuring by reactive atom plasma (RAP)

In this thesis, the research and development of a novel rapid figuring procedure for large ultra-precise optics by Reactive Atom Plasma technology is reported. The hypothesis proved in this research is that a metre scale surface with a form accuracy of ~1 μm PV can be figure corrected to 20 – 30 nm RMS in ten hours. This reduces the processing time by a factor ten with respect to state-of-the-art techniques like Ion Beam Figuring. The need for large scale ultra-precise optics has seen enormous growth in the last decade due to large scale international research programmes. A bottleneck in production is seen in the final figure correction stage. State-of-the-art processes capable of compliance with requisites of form accuracy of one part in 108 (CNC polishing, Magneto-Rheological Finishing and Ion Beam Figuring) have failed to meet the time and cost frame targets of the new optics market. Reactive Atom Plasma (RAP) is a means of plasma chemical etching that makes use of a Radio Frequency Inductively Coupled Plasma (ICP) torch operating at atmospheric pressure. It constitutes an ideal figuring alternative, combining the advantages of a non-contact tool with very high material removal rates and nanometre level repeatability. Despite the rapid figuring potential of this process, research preceding the work presented in this manuscript had made little progress towards design and implementation of a procedure for metre-class optics. The experimental work performed in this PhD project was conducted on Helios 1200, a unique large-scale RAP figuring facility at Cranfield University. Characterisation experiments were carried out on ULE and fused silica surfaces to determine optimum process parameters. Here, the influence of power, surface distance, tool speed and surface temperature was investigated. Subsequently, raster-scanning tests were performed to build an understanding on spaced multiple passes ... [cont.].SAS Prize winne

PLATELETS BEYOND ATHEROTHROMBOSIS

Platelets are nowadays more and more investigated to better characterise their role in many different pathophysiological processes. The present thesis summarises explore NAFLD (Non-Alcoholic Fatty Liver Disease) is a chronic epatopathy degenerating in NASH syndrome and in the worst scenario to liver cancer. Using a Cellix Microfluidic platform with collagen coated microchip and a Flow Cytometry (FACS) on Platelet derived Microvesicles (PMVs) essay, a stronger platelet activity and higher release of PMVs in such patients, is highlighted, probably due to a preactivation platelet status. A platelet activation, leading to wider platelets aggregates, is observed after incubation with C6O4 (100-200 ng/mL), a new compound belonging to Perfluoroalkyl substances (PFAS), used in detergent, coatings for cookware etc. Aspirin 100µM (ASA) shows a neutralisation of C6O4 procoagulant properties. Similar results are observed in FACS analysis on PMVs, regardless the co-stimulation with ADP 7.5µM, TRAP 10µM or in resting cond

Fast figuring of large optics by reactive atom plasma

The next generation of ground-based astronomical observatories will require fabrication and maintenance of extremely large segmented mirrors tens of meters in diameter. At present, the large production of segments required by projects like E-ELT and TMT poses time frames and costs feasibility questions. This is principally due to a bottleneck stage in the optical fabrication chain: the final figuring step. State-of-the-art figure correction techniques, so far, have failed to meet the needs of the astronomical community for mass production of large, ultra-precise optical surfaces. In this context, Reactive Atom Plasma (RAP) is proposed as a candidate figuring process that combines nanometer level accuracy with high material removal rates. RAP is a form of plasma enhanced chemical etching at atmospheric pressure based on Inductively Coupled Plasma technology. The rapid figuring capability of the RAP process has already been proven on medium sized optical surfaces made of silicon based materials. In this paper, the figure correction of a 3 meters radius of curvature, 400 mm diameter spherical ULE mirror is presented. This work demonstrates the large scale figuring capability of the Reactive Atom Plasma process. The figuring is carried out by applying an in-house developed procedure that promotes rapid convergence. A 2.3 μm p-v initial figure error is removed within three iterations, for a total processing time of 2.5 hours. The same surface is then re-polished and the residual error corrected again down to& lambda;/20 nm rms. These results highlight the possibility of figuring a metre-class mirror in about ten hours

Reactive Atom Plasma (RAP) figuring machine for meter class optical surfaces

A new surface figuring machine called Helios 1200 is presented in this paper. It is designed for the figuring of meter sized optical surfaces with form accuracy correction capability better than 20 nm rms within a reduced number of iterations. Unlike other large figuring facilities using energy beams, Helios 1200 operates a plasma torch at atmospheric pressure, offers a high material removal rate, and a relatively low running cost. This facility is ideal to process large optical components, lightweight optics, silicon based and difficult to machine materials, aspheric, and free form surfaces. Also, the surfaces processed by the reactive atom plasma (RAP) are easy to fine polish through hand conventional sub-aperture polishing techniques. These unique combined features lead to a new capability for the fabrication of optical components opening up novel design possibilities for optical engineers. The key technical features of this large RAP machine are fast figuring capabilities, non-contact material removal tool, the use of a near Gaussian footprint energy beam, and a proven tool path strategy for the management of the heat transfer. Helios 1200 complies with the European machine safety standard and can be used with different types of reactive gases using either fluorine or chlorine compounds. In this paper, first the need for large optical component is discussed. Then, the RAP facility is described: radio frequency R.F generator, plasma torch, and 3 axis computer numerically controlled motion system. Both the machine design and the performance of the RAP tool is assessed under specific production conditions and in the context of meter class mirror and lens fabrication

Matter-wave interferometry: towards antimatter interferometers

Starting from an elementary model and refining it to take into account more realistic effects, we discuss the limitations and advantages of matter-wave interferometry in different configurations. We focus on the possibility to apply this approach to scenarios involving antimatter, such as positrons and positronium atoms. In particular, we investigate the Talbot-Lau interferometer with material gratings and discuss in details the results in view of the possible experimental verification.Comment: 18 pages; 8 figure

Synthesis of Prosthesis Architectures and Design of Prosthetic Devices for Upper Limb Amputees

This chapter presents a procedure for the Determination of the Optimal Prosthesis Architecture for upper limb amputees (DOPA). The presented approach can consistently manage both the clinical aspects and the technical issues involved in the design of electromechanically actuated prostheses. The procedure is composed on one hand of algorithms useful for analyzing the patients\u2019 requirements and on the other hand of algorithms that perform kinematic and kinetostatic simulations of several architectures of artificial arms attempting to fulfil important activities of daily living. The systematic evaluation of the prosthesis models\u2019 performance can methodically guide designers in the synthesis of the optimal prosthesis that best suits the patients\u2019 requirements