The experimental research of the electric characteristics of discharge in the quasi-steady plasma accelerator with the longitudinal magnetic field

Installation of the coaxial quasi-steady high-current one-stage plasma accelerator with a longitudinal magnetic field is created. The lead experiments have shown an opportunity of realization of the discharges, formation of the ionization front and generation of the plasma streams at the presence of a longitudinal field in the accelerator channel. The currentvoltage characteristics of the discharge at the presence and absence of a longitudinal field are measured. It is established that a weak longitudinal field does not render the appreciable influence on the integrated characteristics of discharge in the accelerator with the rod anode in an ion current transport regime.Створено установку коаксіального квазістаціонарного сильнострумового одноступеневого плазмового прискорювача з подовжнім магнітним полем. Проведено експерименти, які продемонстрували можливість здійснення розрядів, формування фронту іонізації й генерації потоків плазми за умови існування подовжнього магнітного поля в каналі прискорювача. Виміряні вольтамперні характеристики розряду при наявності та відсутності подовжнього поля. Встановлено, що слабке подовжнє поле не створює значного впливу на інтегральні характеристики розряду в прискорювачі зі стрижневим анодом в режимі іонного струмопереносу.Создана установка коаксиального квазистационарного сильноточного одноступенчатого плазменного ускорителя с продольным магнитным полем. Проведенные эксперименты продемонстрировали возможность осуществления разрядов, формирования фронта ионизации и генерации потоков плазмы при наличии продольного поля в канале ускорителя. Измерены вольтамперные характеристики разряда при наличии и отсутствии продольного поля. Установлено, что слабое продольное поле не оказывает заметного влияния на интегральные характеристики разряда в ускорителе со стрежневым анодом в режиме ионного токопереноса

Erosion mechanisms and erosion products in tungsten targets exposed to plasma heat loads relevant to ELMS and mitigated disruptions in ITER

Tungsten targets were irradiated by intense plasma streams at plasma gun facilities MK-200UG and QSPA-T. The targets were tested by plasma loads relevant to Edge Localised Modes (ELM) and mitigated disruptions in ITER. Material erosion caused by melt motion and by emission of droplets has been studied.Мишени из вольфрама были подвергнуты воздействию интенсивных потоков плазмы на плазменных ускорителях МК-200UG и КСПУ-Т. Испытания проводились при плазменных нагрузках, характерных для ELMов и ослабленных срывов в ITERe. Исследована эрозия материала, обусловленная движением расплава и капельным разбрызгиванием.Мішені з вольфраму були піддані впливу інтенсивних потоків плазми на плазмових прискорювачах МК-200UG і КСПУ-Т. Іспити проводилися при плазмових навантаженнях, характерних для ELMів і ослаблених зривів в ITERі. Досліджено ерозію матеріалу, що обумовлена рухом розплаву і краплинним розбризкуванням.The work is supported by RFBR grant No 09-02-13562

Investigation of erosion mechanisms and erosion products in divertor armour materials under conditions relevant to ELMs and mitigated disruptions in ITER

Carbon fibre composite (CFC) and tungsten were irradiated by intense plasma streams at plasma gun facilities MK-200UG and QSPA-T. The targets were tested by plasma loads relevant to Edge Localised Modes (ELM) and mitigated disruptions in ITER. Onset condition of material erosion and properties of erosion products have been studied.С-С композит і вольфрам були піддані впливові інтенсивних потоків плазми на плазмових прискорювачах МК-200UG і КСПП-Т. Мішені випробувалися при плазмових навантаженнях, характерних для ЭЛМів й ослаблених зривів в ІТЕРі. Були проведені дослідження початкових умов ерозії матеріалів і властивостей продуктів ерозії.С-С композит и вольфрам были подвергнуты воздействию интенсивных потоков плазмы на плазменных ускорителях МК-200UG и КСПУ-Т. Мишени испытывались при плазменных нагрузках, характерных для ЭЛМов и ослабленных срывов в ИТЭРе. Были проведены исследования начальных условий эрозии материалов и свойств продуктов эрозии

Age-associated features of mitochondrial potential (ΔΨm) changes induced by rare-earth based nanoparticles

Age-specific effects of redox-active nanoparticles (NPs) (rare-earth orthovanadates and CeO₂) of various geometrical parameters on mitochondrial potential (ΔΨm) have been studied in isolated rat hepatocytes. It was shown that extra small (1-2 nm) CeO₂ NPs at high concentrations cause a slight decrease of ΔΨm only in the hepatocytes of 3-month-old rats. The orthovanadate NPs suppress ΔΨm in concentration-dependent manner, whereas the sensitivity of mitochondria to the lower NPs concentration is higher for 20 month-old rats. Thiol protector glutathione was shown to prevent completely NPs-induced ΔΨm decrease. For the old animals, thiol protection against the NPs as well as exogenic pro-oxidants (H₂O₂ and t-BHP) action was more expressed. ΔΨm stabilization in the presence of the NPs was observed at pro-oxidant conditions only for the young rats. It was suggested that the reduction of mitochondrial functions under effect of the orthovanadate NPs is due to increase of reactive oxygen species (ROS) production, and it had age-related character and depended on the thiol buffer system

Behavior of divertor and first wall armour materials at plasma heat fluxes relevant to ITER ELMs and disruptions

The paper presents the main results of numerous experiments carried out over the past 10 years at QSPA-T and QSPA-Be plasma guns in support of ITER. Special targets made of pure W, W-1%La2O3 and two types of Be (TGP-56FW and S65-C) were tested under the series of repeated plasma stream and photonic flux impact. Maximum heat load on the target surface was up to 2.5MJ/m2 in the case of plasma testing and was equal to 0.5MJ/m2 in the case of photonic flux testing. Pulse waveform was rectangular with tpulse= 0.5ms. It was found that the main erosion mechanisms of W and Be under plasma stream impact are the melt layer movement, the ejection of droplets and the cracks formation. As a result of repeated photonic fluxes a regular, “corrugated” structure are eventually formed on the Be target surface. Study of erosion products of W formed under plasma stream impact on the W target has shown that the D/W atomic ratio in the deposited W films during pulsed events may be the same or even higher than that for stationary processes. Keywords: ITER, Tungsten, Beryllium, Transient events, Material erosion, Erosion product

Three-dimensional modelling of sputtered materials transport in diagnostic ducts of fusion devices

Migration of plasma erosion products in plasma facilities is studied experimentally and numerically within the framework of modelling transport of plasma-facing materials in the diagnostic ducts of fusion devices. Material transport simulation is discussed for two cases of low and high background neutral gas pressures. Monte Carlo software KITe was used to simulate transport at a neutral gas background pressure 0.1-0.5 Pa – typical during steady-state tokamak operation and during pressure pulses caused by edge localized modes (ELMs). The simulation approach was implemented to describe experiments at the MAGNUM-PSI facility. Fluid dynamic code FLUENT is used to simulate transport during pressure surges as high as 1000 Pa, which can occur in case of severe disruptions in tokamak plasma discharges, such as vertical displacement events (VDE) or accidental events. The hydrodynamic approach was verified in simulation of target sputtering in the QSPA plasma gun facility