Confidence building measures – necessary component establishing Nuclear Weapon Free Zone in the region

DOI: 10.5564/mjia.v0i14.25Mongolian Journal of International Affairs No.14 2007 pp.64-6

Bounce-Averaged Velocity of Trapped Particle Drift in Toroidal Helical SYstems

Abstract The normal to a magnetic surface component of the bounce-averaged velocity of trapped particle drift is investigated. We define this component as vun:6rn/to where 6ro is an excursion of the trapped particle across the magnetic surface during one bounce time zo. A method of computing r"o is considered in case of a stellarator magnetic field given in real-space coordinates, without transforming the field to magnetic coordinates. We also consider an evaluation of neoclassical transport for the L/ v transport regime

Numerical study of the mercier plasma stability and equilibrium plasma currents in an l=2 YAMATOR

In paper [1] a new stellarator-type magnetic system having a high magnetic well value was proposed (later it got the name YAMATOR). In the present work the MHD plasma stability depending from value of the total vertical magnetic field for the magnetic configuration of l=2 variant of a similar system is investigated numerically. To investigate the plasma stability using the Mercier stability criterion, we apply the numerical method based on the calculation of the terms contained in Mercier criterion by tracing the magnetic field lines in the given stellarator magnetic field [3,4]. The magnetic field of helical windings is calculated by the Biot-Savart law. From our analysis of the MHD plasma stability in the trap under consideration it follows that the Mercier stability criterion is satisfied for a great part of the plasma-confinement region, and the violation of this criterion can take place only for the magnetic surfaces from the external part of the plasma column

Can ionic concentration changes due to mechanical deformation be responsible for the neurostimulation caused by focused ultrasound? a simulation study

Objective Ultrasound stimulation is an emerging neuromodulation technique, for which the exact mechanism of action is still unknown. Despite the number of hypotheses such as mechanosensitive ion channels and intermembrane cavitation, they fail to explain all of the observed experimental effects. Here we are investigating the ionic concentration change as a prime mechanism for the neurostimulation by the ultrasound. Approach We derive the direct analytical relationship between the mechanical deformations in the tissue and the electric boundary conditions for the cable theory equations and solve them for two types of neuronal axon models: Hodgkin-Huxley and C-fibre. We detect the activation thresholds for a variety of ultrasound stimulation cases including continuous and pulsed ultrasound and estimate the mechanical deformations required for reaching the thresholds and generating action potentials. Main results We note that the proposed mechanism strongly depends on the mechanical properties of the neural tissues, which at the moment cannot be located in literature with the required certainty. We conclude that given certain common linear assumptions, this mechanism alone cannot cause significant effects and be responsible for neurostimulation. However, we also conclude that if the lower estimation of mechanical properties of neural tissues in literature is true, or if the normal cavitation occurs during the ultrasound stimulation, the proposed mechanism can be a prime cause for the generation of action potentials. Significance The approach allows prediction and modelling of most observed experimental effects, including the probabilistic ones, without the need for any extra physical effects or additional parameters

Numerical study of the 1/ν neoclassical transport and Mercier plasma stability in an l=2 torsatron with the centered planar magnetic axis

The 1/ν neoclassical transport and Mercier plasma stability for a magnetic configuration of l=2 torsatron system with the centered planar magnetic axis, which was done by selecting the winding law of the helical coils, formed in the model of the l=2 torsatron Uragan-2M type, are investigated numerically. For calculating the transport coefficients and Mercier stability criterion a technique, based on integration along magnetic field lines in a given stellarator magnetic field (NEO code) is used. The magnetic field of helical windings is calculated by the Biot-Savart law. The transport coefficients are presented in a standard form containing a factor depending on the magnetic field geometry. The obtained results are compared with corresponding results for two variants of torsatron Uragan-2M «standard» configurationЧисленными методами выполнено исследование неоклассического переноса в режиме 1/ν и МГД-устойчивости плазмы с использованием критерия Мерсье для двухзаходной торсатронной системы с центрированной плоской магнитной осью, что было достигнуто с помощью специального выбора закона навивки винтовой обмотки в модели, близкой по параметрам к параметрам торсатрона Ураган-2М. При вычислении коэффициентов неоклассического переноса в указанном режиме и расчетах величин, входящих в критерий Мерсье, использована техника, основанная на численном интегрировании вдоль силовых магнитных линий в заданном стеллараторном магнитном поле (код NEO). Магнитное поле винтовых проводников вычислялось с использованием закона Био-Савара. Полученные коэффициенты переноса представлены в стандартной форме, содержащей фактор, зависящий от геометрии магнитного поля системы. Выполнено сравнение полученных результатов с соответствующими результатами, полученными ранее для двух вариантов «стандартной» конфигурации торсатрона Ураган-2М.Числовими методами виконано дослідження неокласичного переносу в режимі 1/ν та МГД-стійкості плазми з використанням критерію Мерс’є для l=2 торсатронної системи із центрованою плоскою магнітною віссю, що було досягнуто за допомогою спеціального вибору закону навивки гвинтової обмотки в моделі, близькій за параметрами до параметрів торсатрона Ураган-2М. При обчисленні коефіцієнтів неокласичного переносу в зазначеному режимі та розрахунках величин, що входять у критерій Мерс’є, використана техніка, що базується на числовому інтегруванні уздовж силових магнітних ліній в заданому стелараторному магнітному полі (код NEO). Магнітне поле гвинтових провідників обчислювалося з використанням закону Біо-Савара. Отримані коефіцієнти переносу представлені в стандартній формі, що містить фактор, залежний від геометрії магнітного поля системи. Виконано порівняння отриманих результатів з відповідними результатами, отриманими раніше для двох варіантів «стандартної» конфігурації торсатрона Ураган-2М

Neoclassical transport in KOLER trap (Yamator)

The new stellarator type magnetic system having a high magnetic well value was proposed in paper [1]. In the present work neoclassical transport for magnetic configuration of l = 2 variant of similar system is investigated by numerical methods. A so-called 1/ ν transport regime, in which the transport coefficients are increased with reduction of particle collision frequency ν is considered. For calculating of transport coefficients a technique [2], based on integration along magnetic field lines in given stellarator magnetic field with taking into account particles trapped not only within one magnetic field period but also within several magnetic field periods is used. The obtained transport coefficients are presented in a standard form containing a factor depending on the magnetic field geometry. The dependence of transport coefficients from value of a resulting vertical magnetic field is analysed