Peculiarities of plasma fluctuations during RF heating in Uragan-3M torsatron by means of two alfven waves

Three wave interaction has been observed in experiments on Uragan-3M torsatron. Two RF antennas with frequencies Ω1 and Ω2 were used simultaneously for plasma production and heating. Plasma was probed by microwaves, these allowed to study reflection of microwaves at almost whole plasma radius. Spectral analysis of reflected microwaves showed an existence of plasma density fluctuation with frequency Ω1 – Ω2. The suppression of plasma low frequencies was observed, when the plasma oscillation with Ω1 – Ω2 frequency has appeared. Microwaves probing of these fluctuations is the useful tool for studies of their influence on plasma behavior and possibly RF power absorption profile.Трьоххвильова взаємодія спостерігалась в експериментах на торсатроні Ураган-3М. Дві ВЧ антени з частотами Ω1 і Ω2 одночасно використовувались для створення і нагріву плазми, яка зондувалась мікрохвилями, місце відбиття яких перекривало майже весь радіус. При спектральному аналізі відбитих НВЧ сигналів виявлені флуктуації густини плазми з частотою Ω1 – Ω2. При появі коливань з частотою Ω1 – Ω2 спостерігалось пригнічення НЧ флуктуацій. Мікрохвильове зондування є корисним засобом для вивчення їх впливу на поведінку плазми та, можливо, для відтворення профілю поглинання ВЧ потужності.Трехволновое взаимодействие наблюдалось в экспериментах на торсатроне Ураган-3М. Две ВЧ антенны с частотами Ω1 и Ω2 одновременно использовались для создания и нагрева плазмы, которая зондировалась микроволнами, место отражения которых перекрывало почти весь радиус. При спектральном анализе отраженных СВЧ сигналов обнаружены флуктуации плотности плазмы с частотой Ω1 – Ω2. При появлении колебаний на частоте Ω1 – Ω2 наблюдалось подавление НЧ флуктуаций. Микроволновое зондирование является полезным средством для изучения их влияния на поведение плазмы и, возможно, для воссоздания профиля поглощения ВЧ мощности

Results of the BiPo-1 prototype for radiopurity measurements for the SuperNEMO double beta decay source foils

The development of BiPo detectors is dedicated to the measurement of extremely high radiopurity in $^{208}$Tl and $^{214}$Bi for the SuperNEMO double beta decay source foils. A modular prototype, called BiPo-1, with 0.8 $m^2$ of sensitive surface area, has been running in the Modane Underground Laboratory since February, 2008. The goal of BiPo-1 is to measure the different components of the background and in particular the surface radiopurity of the plastic scintillators that make up the detector. The first phase of data collection has been dedicated to the measurement of the radiopurity in $^{208}$Tl. After more than one year of background measurement, a surface activity of the scintillators of $\mathcal{A}$($^{208}$Tl) $=$ 1.5 $\mu$Bq/m$^2$ is reported here. Given this level of background, a larger BiPo detector having 12 m$^2$ of active surface area, is able to qualify the radiopurity of the SuperNEMO selenium double beta decay foils with the required sensitivity of $\mathcal{A}$($^{208}$Tl) $<$ 2 $\mu$Bq/kg (90% C.L.) with a six month measurement.Comment: 24 pages, submitted to N.I.M.

Spectral modeling of scintillator for the NEMO-3 and SuperNEMO detectors

We have constructed a GEANT4-based detailed software model of photon transport in plastic scintillator blocks and have used it to study the NEMO-3 and SuperNEMO calorimeters employed in experiments designed to search for neutrinoless double beta decay. We compare our simulations to measurements using conversion electrons from a calibration source of $\rm ^{207}Bi$ and show that the agreement is improved if wavelength-dependent properties of the calorimeter are taken into account. In this article, we briefly describe our modeling approach and results of our studies.Comment: 16 pages, 10 figure

Formation of ITB in the vicinity of rational surfaces in the Uragan-3M torsatron

It was shown that there is the possibility of ITB formation in the vicinity of rational surfaces in a torsatron magnetic configuration. The formation of ITB is accompanied by fast change of plasma poloidal rotation velocity, radial electric field and its shear and the decrease of plasma density fluctuations. After the ITB formation the transition to the improved plasma confinement takes place. The transition stars when electron temperature in the region of rational surfaces is sufficient to satisfy the condition υTe/uei>>2πR0 (here υTe is electron thermal velocity and uei is the frequency of ion – electron collisions, and R0 is the major radius of the torus). Such a regime can be maintained during the whole duration of RF discharge without any disturbances.Показано, що існує можливість формування внутрішнього теплового бар’єру (ВТБ) в плазмі ВЧ розряду в околиці раціональних поверхонь в торсатронній магнітній конфігурації. Формування ВТБ супроводжується бистрими змінами швидкості полоідального обертання плазми, радіального електричного поля и його шира і зменшенням флуктуацій густини плазми поблизу раціональних поверхонь. Після формування ВТБ спостерігається перехід в режим поліпшеного утримання плазми. Час переходу зменшується із збільшенням ВЧ потужності нагріву.Показано, что имеется возможность формирования внутреннего теплового барьера (ВТБ) в плазме ВЧ разряда в окрестности рациональных поверхностей в торсатронной магнитной конфигурации. Формирование ВТБ сопровождается быстрыми изменениями скорости полоидального вращения плазмы, радиального электрического поля и его шира и уменьшением флуктуаций плотности плазмы вблизи рациональных поверхностей. После формирования ВТБ наблюдается переход в режим улучшенного удержания плазмы. Время перехода сокращается с увеличением ВЧ мощности нагрева

Output Feedback Control for MIMO systems with Disturbances Compensation

The paper deals with the novel feedback output control law for multiple-input multiple-output (MIMO) plant with mismatched bounded disturbances. The plant model is described by linear and Lipshitz nonlinear terms. The control law is based on the auxiliary loop method for disturbance estimation and modified backstepping method for control under mismatched disturbances. Differently from existing results based on backstepping method the proposed algorithm allows to reduce the accuracy in steady state, while the existing auxiliary loop based algorithm are feasible under matched disturbances. The results in the England Power System Benchmark illustrate the efficiency of the proposed schem

Multi-annual changes of NOx emissions in megacity regions: nonlinear trend analysis of satellite measurement based estimates

Hazardous impact of air pollutant emissions from megacities on atmospheric composition on regional and global scales is currently an important issue in atmospheric research. However, the quantification of emissions and related effects is frequently a difficult task, especially in the case of developing countries, due to the lack of reliable data and information. This study examines possibilities to retrieve multi-annual NOx emissions changes in megacity regions from satellite measurements of nitrogen dioxide and to quantify them in terms of linear and nonlinear trends. By combining the retrievals of the GOME and SCIAMACHY satellite instrument data with simulations performed by the CHIMERE chemistry transport model, we obtain the time series of NOx emission estimates for the 12 largest urban agglomerations in Europe and the Middle East in the period from 1996 to 2008. We employ then a novel method allowing estimation of a nonlinear trend in a noisy time series of an observed variable. The method is based on the probabilistic approach and the use of artificial neural networks; it does not involve any quantitative a priori assumptions. As a result, statistically significant nonlinearities in the estimated NOx emission trends are detected in 5 megacities (Bagdad, Madrid, Milan, Moscow and Paris). Statistically significant upward linear trends are detected in Istanbul and Tehran, while downward linear trends are revealed in Berlin, London and the Ruhr agglomeration. The presence of nonlinearities in NOx emission changes in Milan, Paris and Madrid is confirmed by comparison of simulated NOx concentrations with independent air quality monitoring data. A good quantitative agreement between the linear trends in the simulated and measured near surface NOx concentrations is found in London

Combining deterministic and statistical approaches for PM10 forecasting in Europe

International audienceWell documented adverse health effects of airborne particulate matter (PM) stimulate intensive research aimed at understanding and forecasting its behaviour. Forecasting of PM levels is commonly performed with either statistical or deterministic chemistry-transport models (CTM). In this study, we investigate advantages of combining deterministic and statistical approaches for PM10 forecasting over Europe one day ahead. The proposed procedure involves statistical postprocessing of deterministic forecasts by using PM10 monitoring data. A series of experiments is performed using a state-of-the-art CTM (CHIMERE) and statistical models based on linear regressions. It is found that performance of both CTM simulations and "pure" statistical models is inferior to that of the combined models. In particular, the root mean squared error of the deterministic forecasts can be reduced, on the average, by up to 45 percent (specifically, from 12.8 to 6.9 mu g/m(3) at urban sites in summer) and the coefficient of determination can be almost doubled. Importantly, it is found that the combined models for rural sites in summer and for urban and suburban sites in both summer and winter are representative, on the average, not only for a given monitoring site used for their training, but also of territories of similar type of environment (rural, suburban or urban) within several hundreds of kilometers away