UKAEA Journals

Showing 1641 - 1650 of 1651 Journals Results
1990

This paper reports tests of an electron suppressor, for volume negative ion sources with variable electric and magnetic fields. The experiments have been carried out with a source and accelerator operating d.c. and with an extraction aperture of 16 mm diameter. The results are compared to those obtained with a permanent magnet suppressor and to a t…

Published
1990

The set of semicollisional layer equations derived by Fitzpatrick [Phys. Fluids B 1, 2381 (1989)] is used to investigate the effect of trapped particles on the linear stability of long wavelength resistive modes in a large-aspect-ratio tokamak. At 0( 1) shear, destabilization by trapped particles is found to significantly modify previous cylindrica…

Published
1990

Two designs of electron suppressor have been tested in a volume negative ion source operating dc with a large extraction aperture diameter (16 mm). Both suppressors employ magnetic fields to divert the electrons near the extraction aperture onto collector electrodes. However, while one suppressor uses a fixed field produced by permanent magnets, th…

Published
1989

The large size of future, and possibly present day, tokamaks requires high neutral atom beam energies for current drive and heating. These injectors must also have a high electrical efficiency and this can be achieved using negative ion sources to create the beam. These large tokamaks, such as ITER or NET require a neutral beam power of around 50-1…

Published
1989

When a suitable accelerating voltage is applied to extract negative ions from a volume production source, electrons are also extracted. If no means of suppression is utilized, the electron current in a hydrogen plasma would typically be of the order of 80-100 times the negative-ion current. In the accelerator designs in use at Culham Laboratory, el…

Published
1989

Particle beams have been developed at the Culham Laboratory for many years, mainly for application to the production of high-temperature plasmas. These developments included demonstration offundamental plasma physics such as particle trapping, heating, and current drive coupled to continuous advances in the physics and technology of ion beam produc…

Published
1989

Magnetic feedback control has been used in the DITE tokamak to substantially reduce saturated m = 2, n = 1 instabilities in both Ohmic discharges and discharges with lower-hybrid current drive (LHCD). Feedback has been used for the first time to significantly increase the disruptive density limit in a tokamak. LHCD on DITE stabilizes the sawtooth i…

Published