Liquid metals as a divertor plasma facing material explored using the Pilot-PSI and Magnum-PSI linear devices

Abstract For DEMO and beyond liquid metal plasma facing components are considered due to their resilience to erosion through flowed replacement, potential for cooling beyond conduction and inherent immunity to many of the issues of neutron loading compared to solid materials. The development curve of liquid metals is behind that of e.g. tungsten however and tokamak-based research is currently somewhat limited in scope. Therefore investigation in linear plasma devices can provide faster progress under controlled and well-diagnosed conditions in assessing many of the issues surrounding the use of liquid metals. The linear plasma devices Magnum-PSI and Pilot-PSI are capable of producing DEMO relevant plasma fluxes which well replicate expected divertor conditions, and the exploration of physics issues for tin (Sn) and lithium (Li) such as vapour-shielding, erosion under high particle flux loading and overall power handing are reviewed here. A deeper understanding of erosion and deposition through this work indicates that stannane formation may play an important role in enhancing Sn erosion, while on the other hand the strong hydrogen isotope affinity reduces the evaporation rate and sputtering yields for Li. In combination with the strong re-deposition rates which have been observed under this type of high density plasma this implies an increase in the operational temperature range, implying a power handling range of 20-25 MW m -2 for Sn and up to 12.5 MW m -2 for Li could be achieved. Vapour shielding may be expected to act as a self-protection mechanism in reducing the heat load to the substrate for off-normal events in the case of Sn, but may potentially be a continual mode of operation for Li.</p

Turbulent particle transport in magnetized fusion plasma

The understanding of the mechanisms responsible for particle transport is of the utmost importance for magnetized fusion plasmas. A peaked density profile is attractive to improve the fusion rate, which is proportional to the square of the density, and to self-generate a large fraction of non-inductive current required for continuous operation. Experiments in various tokamak devices (AUG, DIII-D, JET, TCV, TEXT, TFTR) have indicated the existence of an anomalous inward particle pinch. Recently, such an anomalous pinch has been unambiguously identified in Tore Supra very long discharges, in absence of toroidal electric field and of central particle source, for more than 4 minutes [1]. This anomalous particle pinch is predicted by a quasilinear theory of particle transport [2], and confirmed by non-linear turbulence simulations [3] and general considerations based on the conservation of motion invariants [4]. Experimentally, the particle pinch is found to be sensitive to the magnetic field gradient in many cases [5, 6, 7, 8], to the temperature profile [5, 9] and also to the collisionality that changes the nature of the microturbulence [10, 11, 12]. The consistency of some of the observed dependences with the theoretical predictions gives us a clearer understanding of the particle pinch in tokamaks, allowing us to predict more accurately the density profile in ITER.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

LiMeS-Lab:An Integrated Laboratory for the Development of Liquid–Metal Shield Technologies for Fusion Reactors

The liquid metal shield laboratory (LiMeS-Lab) will provide the infrastructure to develop, test, and compare liquid metal divertor designs for future fusion reactors. The main research topics of LiMeS-lab will be liquid metal interactions with the substrate material of the divertor, the continuous circulation and capillary refilling of the liquid metal during intense plasma heat loading and the retention of plasma particles in the liquid metal. To facilitate the research, four new devices are in development at the Dutch Institute for Fundamental Energy Research and the Eindhoven University of Technology: LiMeS-AM: a custom metal 3D printer based on powder bed fusion; LiMeS-Wetting, a plasma device to study the wetting of liquid metals on various substrates with different surface treatments; LiMeS-PSI, a linear plasma generator specifically adapted to operate continuous liquid metal loops. Special diagnostic protection will also be implemented to perform measurements in long duration shots without being affected by the liquid metal vapor; LiMeS-TDS, a thermal desorption spectroscopy system to characterize deuterium retention in a metal vapor environment. Each of these devices has specific challenges due to the presence and deposition of metal vapors that need to be addressed in order to function. In this paper, an overview of LiMeS-Lab will be given and the conceptual designs of the last three devices will be presented.</p

Exclusive neuronal expression of SUCLA2 in the human brain

SUCLA2 encodes the ATP-forming subunit (A-SUCL-) of succinyl-CoA ligase, an enzyme of the citric acid cycle. Mutations in SUCLA2 lead to a mitochondrial disorder manifesting as encephalomyopathy with dystonia, deafness and lesions in the basal ganglia. Despite the distinct brain pathology associated with SUCLA2 mutations, the precise localization of SUCLA2 protein has never been investigated. Here we show that immunoreactivity of A-SUCL- in surgical human cortical tissue samples was present exclusively in neurons, identified by their morphology and visualized by double labeling with a fluorescent Nissl dye. A-SUCL- immunoreactivity co-localized >99% with that of the d subunit of the mitochondrial F0-F1 ATP synthase. Specificity of the anti-A-SUCL- antiserum was verified by the absence of labeling in fibroblasts from a patient with a complete deletion of SUCLA2. A-SUCL- immunoreactivity was absent in glial cells, identified by antibodies directed against the glial markers GFAP and S100. Furthermore, in situ hybridization histochemistry demonstrated that SUCLA2 mRNA was present in Nissl-labeled neurons but not glial cells labeled with S100. Immunoreactivity of the GTP-forming subunit (G-SUCL-) encoded by SUCLG2, or in situ hybridization histochemistry for SUCLG2 mRNA could not be demonstrated in either neurons or astrocytes. Western blotting of post mortem brain samples revealed minor G-SUCL- immunoreactivity that was however, not upregulated in samples obtained from diabetic versus non-diabetic patients, as has been described for murine brain. Our work establishes that SUCLA2 is expressed exclusively in neurons in the human cerebral cortex

Returning home: forced conscription, reintegration, and mental health status of former abductees of the Lord's Resistance Army in northern Uganda

<p>Abstract</p> <p>Background</p> <p>Since the late 1980s, the Lord's Resistance Army (LRA), a spiritualist rebel group in northern Uganda, has killed and mutilated thousands of civilians and abducted an estimated 52,000 to 75,000 people to serve as soldiers, porters, and sex slaves for its commanders. This study examines the types of violence to which former abductees have been exposed and the extent to which these acts have affected their psychological well-being.</p> <p>Methods</p> <p>This is a cross-sectional study of 2,875 individuals selected through a multi-stage stratified cluster sampling design conducted in 8 districts of northern Uganda. Multivariate logistic regressions were performed with symptoms for Post-traumatic Stress Disorder (PTSD) and depression as the main outcome measures.</p> <p>Results</p> <p>One-third of the respondents (33%) self-reported having experienced abduction (49% among the Acholi, the largest tribal group in northern Uganda). Over half (56%) of all the respondents and over two-thirds of those who experienced abduction met the criteria for symptoms of post-traumatic stress disorder (PTSD). Multivariate analysis shows that several factors increased the risk of former LRA abductees developing symptoms of PTSD. These factors included gender (females were more susceptible than males), being a member of the Acholi ethnic group, participating in or witnessing a cumulative number of traumatic events, and encountering difficulties re-integrating into communities after abduction. Factors associated with increased risk of meeting criteria for symptoms of depression included older age of males at the time of abduction, lower score on social relationship scale, high incidence of general traumatic event exposure, high incidence of forced acts of violence, and problems reintegrating into communities after abduction.</p> <p>Conclusion</p> <p>Abduction and forced conscription of civilians has affected the psychological well-being of a significant number of northern Ugandans. The sources of psychological trauma are multiple, ranging from witnessing to being forced to commit violent acts, and compounded by prolonged exposure to violence, often for months or years. Community-based mental health care services and reintegration programs are needed to facilitate the reintegration of former abductees back into their communities.</p