QDB: A new database of plasma chemistries and reactions

One of the most challenging and recurring problems when modeling plasmas is the lack of data on the key atomic and molecular reactions that drive plasma processes. Even when there are data for some reactions, complete and validated datasets of chemistries are rarely available. This hinders research on plasma processes and curbs development of industrial applications. The QDB project aims to address this problem by providing a platform for provision, exchange, and validation of chemistry datasets. A new data model developed for QDB is presented. QDB collates published data on both electron scattering and heavy-particle reactions. These data are formed into reaction sets, which are then validated against experimental data where possible. This process produces both complete chemistry sets and identifies key reactions that are currently unreported in the literature. Gaps in the datasets can be filled using established theoretical methods. Initial validated chemistry sets for SF 6 /CF 4 /O 2 and SF 6 /CF 4 /N 2 /H 2 are presented as examples

Plasma-induced Decolorization of Indigo-dyed Denim Fabrics Related to Mechanical Properties and Fiber Surface Morphology

The aim of this study was to investigate how morphology of fibers is affected by plasma during the process of decolorization by a low-pressure RF plasma (gas, treatment time, and power were varied) and atmospheric pressure industrial corona (number of passages and power). CIE LAB colorimetric system was used for determination of color difference between untreated and differently plasma-treated denim fabrics. Particular emphasis was put on the morphological changes induced by plasma treatment, because they indicate changes in mechanical properties of the fabrics. The morphology of plasma-treated fibers was analyzed by scanning electron microscopy (SEM). SEM images revealed that, when plasma conditions that lead to a decolorization were chosen, specific fiber surface changes were always observed in the form of submicrometer-sized striations, pits, and cracks. Mechanical properties of denim fabrics were moderately influenced by treatment conditions. The results indicated that decolorization was highly affected by plasma parameters and desired worn look effects could be designed by adequate control of plasma processing while paying attention to limiting the plasma-induced damage

Relaxation of low energy positrons in molecular gases

The calculations of thermalization times and spatial relaxation profiles of the positron transport properties in H_2, N_2 and in mixture of N_2 and CF_4 are presented. Recently, the data needed to compile comprehensive set of cross sections for these gases became available which made our calculations possible. The main difference between positron and electron transport is the existence of the effect of positronium (Ps) formation which changes the number of particles and has a strong energy dependence. The relative magnitude of positronium formation to electronic excitations and the relative positions of their thresholds control the efficiency of thermalization and non-conservative transport phenomena. The effect of vibrational and rotational excitations on thermalization has been considered and relative contributions were determined. Our calculated thermalization data are in reasonably good agreement with the experimental data of Al-Qaradawi et al. (2000)

Positron and electron interactions and transport in biological media: modelling tracks and radiation damage

We present Boltzmann and Monte Carlo models of positron and electron transport in water, in the vapour and liquid states, which are based on measured and calculated cross section data that has been compiled into "complete" cross section sets for both positrons and electrons. The cross section measurements, transport theory, and implications for the study of charged particle transport in soft matter are discussed

Low energy electron and positron transport in biologically relevant materials

Peer Reviewe

Modelling single positron tracks in Ar

In this study, we present a complete set of positron interaction cross sections for scattering from Ar, for incident energies ranging from 0 to 10 keV. Experimental data have been critically reviewed from previous experiments performed at the Australian National University and University College London. Differential and integral cross sections, including the effect of positronium formation, have been calculated by using two different optical potential methods. The results of these calculations, in combination with experimental cross sections and experimental energy-loss spectra, have been established as input parameters for an event-by-event Monte Carlo simulation procedure to generate single positron tracks in argon. The reliability of this method to obtain energy deposition models at the nano-scale is also discussed. © 2012 IOP Publishing Ltd.This work has been carried out with partial financial support of the Spanish Ministerio de Ciencia e Innovacion´ (Project FIS2009-10245), the European Science Foundation (COST Actions CM0601 and MP1002) and the Australian Research Council’s Centre of Excellence Program.Peer Reviewe