Tuneable FEM system as a plasma source for biological applications
There is increasing interest in the use of microwave power for industrial applications. A pulsed tuneable microwave source is beneficial as it allows the high electromagnetic field of a high power to be applied to a target without excessive heating. The free electron maser (FEM) is the tuneable source with ability to operate across a wide range of frequencies from 8 to 20 GHz. Using higher frequencies than the common 2.45 magnetron, increases the fields obtained and also beneficial scaling effects on some applications, such as microwave induced plasmas. The paper presents the basic principles of the FEM system as well as the applications of UV.
Plasma sources using long linear microwave field applicators: main features, classification and modelling
Microwave plasma sources using elongated field applicators that extend over distances large in comparison with the free-space wavelength are in demand for many applications, mainly for the processing of large surfaces of materials that can be moved transversely with respect to the applicator. Various long applicators have been presented in the literature but no unified description is available to assist the potential user in selecting the one best suited for his or her particular needs. This paper is intended to meet this need. All applicators of this kind provide an electromagnetic wave from which originates the electric field sustaining the discharge. However, they differ in some essential aspects which reflect on their performance and on the modelling of the resulting plasma. We propose to classify these applicators first into two main categories according to the way the power flows to the plasma: (i) transmission-line applicators; and (ii) antenna applicators. Then, in each category, we need to distinguish two possible wave characters: travelling and standing. This leaves us with four systems to examine. For each of these systems, we briefly approach discharge modelling, mainly to examine the longitudinal distribution of plasma properties and establish guidelines for the methodical design and operation of these plasma sources. Finally, we evaluate the advantages and disadvantages of the four systems.
Modification of Surfaces and Surface Layers by Non Equilibrium Processes
Plasmas are examples of non-equilibrium phenomena which are being used increasingly for the synthesis and modification of materials impossible by conventional routes. This paper introduces methods available by describing the construction and characteristics of some equipment used for the production of different types of plasmas and other non-equilibrium phenomena. This includes high energy ion beams. The special features, advantages and disadvantages of the techniques will be described. There are a multitude of potential applications relevant to electronic, metallic, ceramic, and polymeric materials. However, scale-up from the laboratory to production equipment depends on establishing a better understanding of both the physics and chemistry of plasmas as well as plasma-solid interactions. Examples are given of how such an understanding can be gained. The chemical analysis of polymer surfaces undergoing modification by inert gas, hydrogen or oxygen plasmas is shown to give physical information regarding the relative roles of diffusion of active species, and direct and radiative energy transfer from the plasma. Surface modification by plasma depositing a new material onto an existing substrate is discussed with particular reference to the deposition of amorphous carbon films. Applications of the unique properties of these films are outlined together with our current understanding of these properties based on chemical and physical methods of analysis of both the films and the plasmas producing them. Finally, surface modification by ion beams is briefly illustrated using examples from the electronics and metals industries where the modification has had a largely physical rather than chemical effect on the starting material.