A plasma is studied in an experimental arrangement called CABINET, which consists of a duoplasmatron as plasma source at one end and a 8000 litre/sec diffusion pump at the other end of a glass cylinder surrounded by magnetic field coils. The plasma drifts continuously along the axis into a magnetic bottle, the maximum magnetic induction in the centre being 4000 gauss. The plasma (mainly hydrogen) was studied in two pressure ranges.In the first pressure range, p = 10−5 torr (L ≪ λi) and Te ≃ 12 eV, Ti∼10 eV, ne (at centre) up to 2 × 1010 cm−3. Large radial electric fields are present, varying from ∼-100 V/cm (at r = 1 cm) to +10 V/cm (at r=3 cm). Azimuthal currents are detected in agreement with the relation j × B = ∇p.In the second pressure range, p = 10−3 torr (L ≫ λi) and Te ≃ 1 eV, Ti∼0.1 eV, ne (at centre) possibly up to 5 × 1013 cm−3. The radial electric fields are one order of magnitude smaller than at 10−5 torr.The plasma density was derived mainly from electron and ion currents to a Langmuir probe, the higher densities in the centre also with microwaves and spectrographically.In both pressure ranges the ion density decreases exponentially with radius between 1 cm and 4 cm from the axis, with an e-folding length depending as B−1 on the magnetic induction. Then a "kink" occurs; this kink moves closer to the axis with increasing magnetic induction. A critical discussion is given concerning determination of the perpendicular diffusion coefficient from measurements of the radial distribution of ions.
Density behaviour and particle losses in RF discharge plasmas of the URAGAN-3M torsatron