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Accurately predicting the pedestal structure in high-(H-)confinement mode plasmas is of great importance for the modelling of future tokamak plasmas. The main predictions of a model of pedestal structure based on paleoclassical transport as the main transport mechanism are presented. Numerical evaluations of this model are compared with a database of measured DIII-D H-mode pedestal profiles. Across the database, the electron temperature gradient is overpredicted by a factor of 1.7 ± 1.1 and the electron density by a factor of 2.1 ± 0.7. These results are consistent with paleoclassical transport producing the minimum level of electron transport. Trends in the predictions indicate that some additional transport may be operative, especially in high βp and low confinement plasmas. [ABSTRACT FROM AUTHOR]

Detailed measurements in two dimensions by probes and Thomson scattering reveal unexpected local electric potential and electron pressure (Pe) maxima near the divertor X point in L-mode plasmas in the DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)]. The potential drives EXB circulation about the X point, thereby exchanging plasma between closed and open magnetic surfaces at rates that can be comparable to the total cross-separatrix transport. The potential is consistent with the classical parallel Ohm's law. A simple model is proposed to explain the pressure and potential hills in low power, nearly detached plasmas. Recent two-dimensional edge transport modeling with plasma drifts also shows X-point pressure and potential hills but by a different mechanism. These experimental and theoretical results demonstrate that low power tokamak plasmas can be far from poloidal uniformity in a boundary layer just inside the separatrix. Additional data, although preliminary and incomplete, suggest that EXB circulation across the separatrix might be a common feature of low confinement behavior. [ABSTRACT FROM AUTHOR]

Presents a study which provided an overview of a scattering diagnostic computer software used in data acquisition, processing and its implementation. Application of the software to magnetic fusion research on tokamak; Details on the computer hardware requirements of the software.

We describe an approach to Thomson scattering diagnostic that relies upon a high power CW laser cavity and a rf signal detection technique, instead of the more usual pulsed high energy laser. The system has three major elements: an ultra long (∼150 m) laser resonance cavity that includes the plasma region; an array of CW diode lasers of high power and high modulation frequency that pumps and maintains the average cavity energy (∼10 mJ); and a lock-in detection system of narrow frequency bandwidth (∼2 kHz). The resonance cavity consists of a pumping chamber for power input from diode lasers, and many relay chambers (∼30) distributed across the plasma cross section for Thomson measurement. The cavity has a low energy loss (∼2% round trip) and zero output power. It is estimated that signal-to-noise of the system is ∼100 times better than the present pulsed system on DIII-D Tokamak due to the increase in usable laser energy and the improved background signal rejection. [ABSTRACT FROM AUTHOR]

Background: Central venous catheters (CVC) are a potential source of bacteraemia and have been associated with increased mortality in haemodialysis patients. We aimed to investigate the relationships between haemodialysis vascular access, taking into account changes in vascular access type during patients' lives, and cause specific mortality risk in a national cohort of dialysis patients., Methods: Prospective cohort study including all patients receiving haemodialysis in Scotland at annual cross sectional surveys in 2009, 2010 and 2011. Data were collected through the Scottish Renal Registry and by a structured review of case records following death. Cox proportional hazards regression and multivariable logistic regression were used to model survival and risk of death from septicaemia respectively., Results: Of a cohort of 2666 patients, 873 (32%) died during follow-up. After case-mix adjustment, patients using only tunnelled CVC during follow-up had a higher risk of all cause mortality across all strata of prior renal replacement therapy exposure [adjusted hazard ratio (HR): 1.83-2.08]. Case-mix adjusted risks of cardiovascular death (adjusted HR: 2.20-2.95) and infection-related death (adjusted HR: 3.10-3.63) were also higher in this group. Patients using tunnelled CVCs during follow-up and prior to death had 6.9-fold higher odds of death from septicaemia compared with those using only arteriovenous fistulae or grafts., Conclusion: Compared with an arteriovenous fistula or graft, sustained use of tunnelled CVCs for vascular access is associated with higher risks of all-cause, cardiovascular and infection-related mortality.