Interaction of supra-thermal ions with turbulence in a magnetized toroidal plasma

This thesis addresses the interaction of a supra-thermal ion beam with turbulence in the simple magnetized toroidal plasma of TORPEX. The first part of the thesis deals with the ohmic assisted discharges on TORPEX. The aim of these discharges is the investigation of the open to closed magnetic field line transition. The relevant magnetic diagnostics were developed. Ohmic assisted discharges with a maximum plasma current up to 1kA are routinely obtained. The equilibrium conditions on the vacuum magnetic field configuration were investigated. In the second part of the thesis, the design of the fast ion source and detector are discussed. The accelerating electric field needed for the fast ion source was optimized. The fast ion source was constructed and commissioned. To detect the fast ions a specially designed gridded energy analyzer was used. The electron energy distribution function was obtained to demonstrate the efficiency of the detector. The experiments with the fast ion beam were conducted in different plasma regions of TORPEX. In the third part of the thesis numerical simulations are used to interpret the measured fast ion beam behavior. It is shown that a simple single particle equation of motion explains the beam behavior in the experiments in the absence of plasma. To explain the fast ion beam experiments with the plasma a turbulent electric field must be used. The model that takes into account this turbulent electrical field qualitatively explains the shape of the fast ion current density profile in the different plasma regions of TORPEX. The vertically elongated fast ion current density profiles are explained by a spread in the fast ion velocity distribution. The theoretically predicted radial fast ion beam spreading due to the turbulent electric field was observed in the experiment

Sources and detectors of fast ions for basic devices

The physics of supra thermal test ions in turbulent plasmas can be conveniently studied in basic plasma physics devices, which allow high-resolution measurements of plasma and fast ion parameters and wave fields throughout the whole plasma cross-section. We describe recent advances in the development of an experimental setup consisting of a non-perturbative Li 6+ miniaturized ion source and a detector for the investigation of the interaction between supra thermal ions and drift/interchange–driven turbulence on the TORPEX device. We present first measurements of the spatial and energy space distribution of the fast ion beam in different plasma scenarios, in which the plasma turbulence is fully characterized. We also discuss the possibility of using the fast ion source in basic plasma devices for fusion. This work is partly funded by the Fonds National Suisse de la Recherche Scientifique

Successful surgical treatment of a patient with combined gunshot shrapnel injuries in the heart and brain complicated by middle cerebral artery pseudoaneurysm

Successful step-by-step treatment of a combined gunshot shrapnel injury of the brain, damaging the left middle cerebral artery (MCA) branches, and penetrating myocardium injury is discussed. Open brain and heart surgeries were performed. A left MCA pseudoaneurysm was formed postoperatively. Endovascular exclusion of the left MCA pseudoaneurysm was performed using detachable micro coils. Finally, plastic reconstruction of the posttraumatic cranial vault defect was performed using a dynamic titanium plate. Treatment of severe combined gunshot shrapnel brain injury with formation of MCA pseudoaneurysm and a penetrating myocardium injury requires a multimodal approach involving related specialists (neurosurgeon, cardiosurgeon and interventional radiologist)

Understanding SDBD Actuators: An Experimental Study on Plasma Characteristics

The working mechanisms of surface dielectric barrier discharge (SDBD) plasma actuators foreseen as aerodynamic control devices is investigated experimentally on a common platform, referred to as the NATO-AVT-RTO-190 test case. A better understanding of the working principle and characteristics of SDBD paves the way for more efficient and safe use of plasma actuators in aerodynamic applications. In this study, a characterisation of the plasma is done by current measurements, fast-camera plasma imaging and force measurements. Furthermore, more advanced plasma characteristics such as reduced electric field and excited species population are found by Optical Emission Spectroscopy. The collective goal of this research is to contribute to a database which can also be used for numerical verification and validation by varying the key parameters such as frequency and voltage

Cross-field plasma blob motion in an open magnetic field line configuration

The radial propagation of blobs generated from plasma instabilities is investigated in an open magnetic field line configuration. Blob cross-field velocities and sizes are obtained from internal probe measurements using pattern recognition. By varying the ion mass, the normalized vertical blob scale a approximate to is scanned from a approximate to 1. An analytical expression for the blob velocity including cross-field ion polarization currents, parallel currents to the sheath, and ion-neutral collisions is derived and shows good quantitative agreement with the experimental data. In agreement with previous theoretical studies, this scaling shows that, for a approximate to 1 it is limited by parallel currents to the sheath

Optimization of surgical treatment of combination of cerebral aneurysms and head magistral arteries stenosis and occlusion

Objective. Determination of the optimal strategy of surgical treatment of patients with a combination of cerebral aneurysms and head magistral arteries stenosis.Methods. 26 patients with combination of cerebral aneurysms and head magistral arteries stenosis, whose age was between 44 and 84 years, have been examined and treated in the Cerebrovascular Clinic of the Dnipropetrovsk Regional Hospital for the last 4 years. 21 of them were operated, 5 – abstained. 24 endovascular and 8 open operations were performed in different combinations.Results. All cases were divided into 3 groups according to the application different tactics of surgical treatment. Group 1 - 10 patients were operated in order to exclude cerebral aneurysm and revascularize head magistral arteries. Group 2 - 5 patients were operated to remove only the head magistral arteries stenosis. Group 3 - 6 patients were operated to exclude cerebral aneurysm alone. Functional outcomes evaluated by the modified Rankin scale and were the best in group 1.Conclusion. Surgical risks in case of treatment only one of pathology in case of combination of head magistral arteries stenosis and cerebral aneurysms may cause clinical manifestation of the other one. One-session surgical treatment of cerebral aneurysms and head magistral arteries stenosis based on data about the peculiarities of collateral bloodcirculation, cerebrovascular reserves, degree hemoperfusion deficit in different arterial basins is the best strategy of surgical treatment