High resolution temperature and density profiles during the energy quench of density limit disruptions in Rijnhuizen tokamak project

Measurements of the electron temperature, Te, and density, ne, during the energy quench of a major disruption showed that the onset of Te erosion in the neighborhood of the m/n = 2/1 O point at the low field side (LFS) accelerates the well-known m/n = 1/1 erosion of the core temperature. During this phase Te(r) is only partially flat in the region between the q = 2 and the q = 1 surfaces and ne(r) decreases in the core and increases inside the m/n = 2/1 island. Immediately after the flattening of Te(r) a large peak in Te and to a lesser extent in ne has been observed. This peak is radially localized at the q = 2 radius at the LFS, is very short lived and is poloidally asymmetric. Te profiles measured by the heterodyne radiometer and the Thomson scattering agree very well up to the time Te(r) flattens but afterwards can be a factor of two different

Interplay between intrinsic plasma rotation and magnetic island evolution in disruptive discharges

The behavior of the intrinsic toroidal rotation of the plasma column during the growth and eventualsaturation of m/n = 2/1 magnetic islands, triggered by programmed density rise, has been carefully investigatedin disruptive discharges in TCABR. The results show that, as the island starts to grow and rotate at aspeed larger than that of the plasma column, the angular frequency of the intrinsic toroidal rotation increasesand that of the island decreases, following the expectation of synchronization. As the island saturates at alarge size, just before a major disruption, the angular speed of the intrinsic rotation decreases quite rapidly,even though the island keeps still rotating at a reduced speed. This decrease of the toroidal rotation is quitereproducible and can be considered as an indicative of disruption

Characterization of toroidal intrinsic rotation with MHD activity in theTCABR tokamak

Plasma rotation has an important play in stabilization of MHD modes and reducing turbulenttransport of particles and energy. Because in fusion reactors it is expected the torque provided byexternal sources will be small, the intrinsic (or spontaneous) rotation is of great interest[1, 2, 3].Furthermore, the origin and physics of plasma rotation is also an important issue by itself.The behavior of the intrinsic toroidal rotation during the growth and saturation of m/n =2/1 magnetic islands, triggered by programmed density ramp up, has been investigated in Lmodeohmic discharges in the TCABR tokamak. In those discharges R = 0.61 m, a = 0.18 m,Ip 80 kA, Bt = 1.07 T, q(a) 3.5 and the toroidal spontaneous rotation of the plasma coreis in the counter-current direction. The results show that the plasma is accelerated as the islandstarts to grow, while the island frequency slows down. And, as the island saturates, the toroidalrotation decreases quite rapidly (faster than the island), and the discharge is followed by a majordisruption. In some discharges, where the density decreases after the island saturation (and thus,avoiding the plasma disruption), the MHD instability becomes smaller until it vanishes, and thetoroidal rotation slows down to its original value before the gas injection

Measurements of the natural plasma flow during the precursor of TCABR density limit disruptions

Magnetic islands are known to degrade confinement of energy and particles in tokamak plasmas.They are also present in the precursor of density limit disruptions being observed untilthe onset of the energy quench of the disruption. The subject of the effect of plasma flow ontearing mode stability has been studied both theoretically [1] and experimentally [2]. Howeverthe experimental work has focused on plasmas with Neutral Beam Injection (NBI), which addshigh momentum to both the plasma and the island, deviating them from their natural velocities.It is important to know the plasma/island rotation behavior without NBI, not just to know theirnatural values but because future large tokamaks, like ITER, are expected to have low plasmarotation due to both large plasma inertia and low applied torque. In this work we will showexperimental values of the ion velocity and the magnetic island velocity measured in TCABRohmic plasmas, without NBI, and during the precursor of a density limit disruption. In this wayit was possible to compare the natural plasma velocity with the island velocity. The ion velocitywas inferred from Doppler spectroscopy of the impurity lines of CVI. Details of this diagnosticsystem and an error analysis of the measured signal can be found in [3]. With the present set up,the toroidal velocity can be measured with time resolution equivalent to 600 Hz and precisionsomewhat better than 5 km/s

State Britain and the art of (Im)proper democratic protest

The installation of Mark Wallinger’s State Britain in the Duveen Galleries of Tate Britain recreated Brian Haw’s protest opposite the Houses of Parliament, which had largely been dismantled by the police under the Serious Organised Crime and Police Act 2005. Wallinger’s work bisected a boundary created by the Act inside which the police could be given greater than usual powers to control demonstrations. The intersection exemplified how, when understood in terms of the performative after Jacques Derrida, art may unsettle the ways in which both the law and aesthetics work to protect the political establishment. aesthetics work to protect the political establishment

The evolution of diabetic chronic complications after pancreas transplantation

Pancreas transplantation is an invasive procedure that can restore and maintain normoglycemic level very successfully and for a prolonged period in DM1 patients. The procedure elevates the morbimortality rates in the first few months following the surgery if compared to kidney transplants with living donors, but it offers a better quality of life to patients

Kidney transplant in diabetic patients: modalities, indications and results

<p>Abstract</p> <p>Background</p> <p>Diabetes is a disease of increasing worldwide prevalence and is the main cause of chronic renal failure. Type 1 diabetic patients with chronic renal failure have the following therapy options: kidney transplant from a living donor, pancreas after kidney transplant, simultaneous pancreas-kidney transplant, or awaiting a deceased donor kidney transplant. For type 2 diabetic patients, only kidney transplant from deceased or living donors are recommended. Patient survival after kidney transplant has been improving for all age ranges in comparison to the dialysis therapy. The main causes of mortality after transplant are cardiovascular and cerebrovascular events, infections and neoplasias. Five-year patient survival for type 2 diabetic patients is lower than the non-diabetics' because they are older and have higher body mass index on the occasion of the transplant and both pre- and posttransplant cardiovascular diseases prevalences. The increased postransplant cardiovascular mortality in these patients is attributed to the presence of well-known risk factors, such as insulin resistance, higher triglycerides values, lower HDL-cholesterol values, abnormalities in fibrinolysis and coagulation and endothelial dysfunction. In type 1 diabetic patients, simultaneous pancreas-kidney transplant is associated with lower prevalence of vascular diseases, including acute myocardial infarction, stroke and amputation in comparison to isolated kidney transplant and dialysis therapy.</p> <p>Conclusion</p> <p>Type 1 and 2 diabetic patients present higher survival rates after transplant in comparison to the dialysis therapy, although the prevalence of cardiovascular events and infectious complications remain higher than in the general population.</p

Modelling of the effect of ELMs on fuel retention at the bulk W divertor of JET

Effect of ELMs on fuel retention at the bulk W target of JET ITER-Like Wall was studied with multi-scale calculations. Plasma input parameters were taken from ELMy H-mode plasma experiment. The energetic intra-ELM fuel particles get implanted and create near-surface defects up to depths of few tens of nm, which act as the main fuel trapping sites during ELMs. Clustering of implantation-induced vacancies were found to take place. The incoming flux of inter-ELM plasma particles increases the different filling levels of trapped fuel in defects. The temperature increase of the W target during the pulse increases the fuel detrapping rate. The inter-ELM fuel particle flux refills the partially emptied trapping sites and fills new sites. This leads to a competing effect on the retention and release rates of the implanted particles. At high temperatures the main retention appeared in larger vacancy clusters due to increased clustering rate