Recent results of studies of magnetic field distribution and neutron scaling on PF-1000 and PF-3 facilities

The recent results of studies of the magnetic field distribution and the neutron yield scaling in two largest plasma focus facilities, PF-3 and PF-1000 is done. The power-law dependence of the neutron yield on the current in the imploding plasma sheath has been demonstrated experimentally. For the first time the presence of the Вz magnetic field components is experimentally shown. In the compression stage, the axial component of the magnetic field reaches several kG that comprises ~10 % of the azimuthal component. The presence of the Bz field is a powerful argument in favor of the existence of closed magnetic configurations, which play an important role in the generating of neutrons.Представлены результаты последних исследований распределения магнитного поля и скейлинга нейтронного выхода на двух крупнейших плазмофокусных установках ПФ-3 и ПФ-1000. Экспериментально показана степенная зависимость нейтронного выхода от величины тока в сжимающейся плазменной оболочке. Впервые экспериментально показано наличие Вz-компоненты магнитного поля. В стадии сжатия величина аксиальной компоненты магнитного поля достигает нескольких килограмм-сил, что составляет ~ 10% от величины азимутальной компоненты. Наличие Bz-поля является весомым аргументом в пользу существования замкнутых магнитных конфигураций, играющих важную роль в механизме генерации нейтронов.Представлено результати останніх досліджень розподілу магнітного поля і скейлінга нейтронного вихoдy на двох найбільших плазмофокусних установках ПФ-3 та ПФ-1000. Експериментально показана ступенева залежність нейтронного виходу від величини струму в плазмовїй оболонці, що стикається. Вперше експериментально показано наявність Вz-компоненти магнітного поля. У стадії стиснення величина аксіальної компоненти магнітного поля досягає декількох кілограм-сил, що складає ~ 10 % від величини азимутальної компоненти. Наявність Вz-поля є вагомим аргументом на користь існування замкнутих магнітних конфігурацій, що мають неаби яку роль у механізмі генерації нейтронів

Magnetic field measurements on PF - 1000 and PF - 3 facilities: current sheath structure and neutron scaling

The comparative analysis of the magnetic field distribution, the dynamics and structure of the plasma current sheath, and the neutron yield scaling in two largest plasma focus facilities, PF-3 and PF-1000 is done. The power-low dependence of the neutron yield on the current in the imploding plasma sheath has been demonstrated experimentally. For the first time the presence of the Bz magnetic field components is experimentally shown

Dena, a new PF device

In this paper we are going to introduce “Dena”, a new Filippov type plasma focus facility, with a condenser bank of 0.288 mF, and a maximum supplying energy of 90 kJ (at Vmax= 25 kV). The facility was installed and started to work in the first quarter of the year 2000. Major points of the paper are: – Dena’s construction, functionality, and diagnostic system. – Preliminary results: Different modes of neutron, X-ray, and “hot spot” production, as well as the possibility of controlling operational mode, by changing anode configuration and initial discharge condition

Studies of interaction of plasma jets generated in a plasma focus facility with an ambient plasma in external magnetic field

The aim of the present experiments was to reproduce and to study in laboratory quasi-perpendicular supercritical collisionless shocks similar to the Earth-Solar Wind shock, by using a plasma focus facility as the plasma source. The experiments were performed on the PF-3 facility (Filippov-type plasma focus) at a level of energy supply of about 1 MJ. Directed plasma jets are produced with axial velocities ~107 cm/s after compression of a plasma-current sheath in the initial stage of plasma focus formation. These jets then travel through an ambient plasma resulting in early gas ionization by X-ray radiation from the plasma focus, and at an angle of 90° to the 2500 G external magnetic field applied by a system based on rear-earth magnets. Our experimental conditions allowed us to reach a range MA ~ 5÷10

Reduced core transport in T-10 and TEXTOR discharges at rational surfaces with low magnetic shear

It has been observed in the T-10 tokamak that immediately after off-axis electron cyclotron resonance heating (ECRH) switch-off, the core electron temperature stays constant for some time, which can be as long as several tens of milliseconds, i.e. several energy confinement times (tau(E)), before it starts to decrease. Whether or not the effect is observed depends critically on the local magnetic shear in the vicinity of the q = 1 rational surface, which should be close to zero. It is hypothesized that a small shear can induce the formation of an internal transport barrier. Measurements of density fluctuations in the transport barrier with a correlation reflectometer show immediately after the ECRH switch-off a clear reduction in the fluctuation level, corroborating the above results. The delayed temperature decrease has also been observed in similar discharges in the TEXTOR tokamak; however, the delay is restricted to similar to1 x tau(E)