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No description available.

No description available.

No description available.

The free electron laser (PEL) is a source of microwave power which makes use of the interaction between the electron beam and electromagnetic radiation. In recent years, most effort in FEL research has been concentrated on producing high power sources of tuneable radiation using high relativistic electron beams. This approach requires accelerators operating at megavolts potential using pulsed-power techniques. Hence, typical FELs are produced in large-scale facilities. The purpose of this research is to bring the FEL back to the world of industrial processing, for which the FEL offers the prospect of a microwave source with a broad tuning range, high power and reasonable efficiency which is higher than the conventional FEL devices. At the University of Liverpool, we are developing a prototype pre-bunched free electron maser (pFEM) that is compact, powerful and efficient fOf industrial applications, using available and affordable technology. The design, set-up and experimental result of this novel X-band rectangular waveguide PFEM are presented. Our device operates at 10 GHz and employs two rectangular waveguide cavities (one for velocity modulation and the other for energy extraction). The electron beam used in this experiment is produced by thermionic electron gun which operates at 3 kV and produces beam current up to 5 rnA. The resonant cavity consists of a thin gap section of height 1.5 mm which reduces the beam energy required for beam wave interaction. EM wave is used to pre-bunch the electrons, instead of using permanent wiggler magnets in conventional FEL system. A phase shifter is installed to ensure the correct phase of the bunched electrons and the EM wave in the output cavity. This novel design allows the PFEM to operate at a low current and accelerating voltage, maintaining a compact design. The experimental result has demonstrated that coherent emission and gain with a beam current of up to 5 rnA can be achieved. The gain curve has an interference pattern due to the phase variations ofthe electrons relative to the EM wave.

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This thesis examines the radiative transfer of extreme ultra-violet (EUV) lasers in plasmas. Harmonic generation, free electron lasers and plasma-based EUV lasers are first reviewed. The accuracy of the Linford formula used to evaluate amplified spontaneous emission (ASE) is examined. A quantitative discussion of backlighters is presented. The maximum plasma thickness able to be probed using extreme ultraviolet (EUV) and harder (1 keV) x-rays is evaluated. It is shown that at higher plasma temperatures (~ 200 eV), EUV radiation (e.g. photon energy = 89 eV) can probe greater optical depth of plasma than x-ray radiation (e.g. photon energy = 1243 eV). The effect of a seed beam injected into an amplifier plasma medium is investigated. TJ1e variation of plasma refractive index with frequency is investigated using the Kramers-Kronig relationship to check the effect ofhigh absorption or gain in a plasma on EUV light. It is shown that a coherent spectral line transmits through absorbing or amplifying plasmas in a near identical manner to incoherent light.

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This thesis describes the development and implementation of fibre-coupled, micron-scale optical resonators for the detection and manipulation of neutral atoms. The resonators are intended for integration with atom chips. The latter are microfabricated devices which enable the cooling, trapping, gUiding and manipulation of atoms by means of optical, magnetic and electric fields. The fields are generated in part using micro-fabricated features on the surface of the chips. Optical cavities are among the most important tools in the study of the interactions between light and matter. They allow the observation of fundamental processes in quantum optics, based on the enhanced coupling of atomic transitions to light fields. Our resonators have mode volumes which are two orders of magnitude smaller than those used in typical cavity quantum electrodynamics experiments. Together with their high quality factors, this leads to large enhancement factors, rendering them ideal for the detection and manipulation of atoms on chips. They are scalable and directly fibre-coupled, both of which are qualities of interest for their implementation in quantum information-processing applications. In the thesis, the optical characteristics of the resonators are explained, as well as the basic principles of the interaction of atoms with their light field. The setup used for the test implementation of the devices is presented, together with early experimental results. These include the detection of atoms via their effect on the cavity reflection spectrum, and the detection of enhanced atomic fluorescence into the cavity mode. The thesis concludes with an outlook on further experimentation, possible improvements of the devices themselves, and a view on their integration with existing atom chip technology.