Electric lamp and discharge devices – With positive or negative ion acceleration
Patent
1997-02-20
1998-08-25
O'Shea, Sandra L.
Electric lamp and discharge devices
With positive or negative ion acceleration
3133611, H01J 152
Patent
active
057986029
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNOLOGY
This invention relates to the field of ion plasma technologies, specifically to a plasma accelerator with closed electron drift.
BACKGROUND ART
Known is a plasma accelerator with closed electron drift, designed for producing thrust on board spacecraft (C. D. Grishin, L. V. Leskov "Electrical rocket engines for spacecrafts" /Moscow/, Mashinostrojenie 1989, page 143).
The given accelerator contains an annular discharge chamber having side walls made of dielectrical material, and a channel, wherein a box-like anode is located, which is made as an integral unit with a gas distributor.
Besides, the accelerator comprises a magnetic system having magnetic poles located on both sides of the discharge chamber and interconnected by magnetic circuits with magnetizing coils, and a cathode-neutralizer.
The specified embodiment of the known accelerator provides ionization of the supplied operating gas by bombardment of electrons drifting within crossed radial magnetic and longitudinal electric fields. After ionization, some of the produced ions are accelerated in the electric field generated by difference of potentials built up between the cathode and the anode. The accelerated ion flow is being neutralized at the accelerator outlet by electrons coming from the cathode-neutralizer.
However, during ionization and acceleration a significant part of ions experience collisions against side walls of the discharge chamber, and this leads to ion recombination and, consequently, to energy losses. Besides, collison of the accelerated ions with walls at the outlet of the discharge chamber causes sputtering of the wall material and, hence, to a decrease in the accelerator life.
Also known is a plasma accelerator with closed electron drift (EP, AI, 0541309), having an annular discharge chamber defined by inner and outer circular side walls and having a channel including an operating gas ionization zone and a gas ion acceleration zone. In the discharge chamber channel there is a box-like anode--gas distributor located at the outlet of the discharge chamber at a distance which it not smaller than the distance between its side walls. Besides, the accelerator comprises a magnetic system having inner and outer magnetic poles interconnected by magnetic circuits with magnetic field sources mounted thereon an inner magnetic screen and an outer magnetic screens located on the external side of the discharge chamber close to its inner and outer side walls, respectively, with gaps relative to the corresponding magnetic poles, and a cathode-neutralizer.
The presence of the magnetic screens made it possible to arrange in the discharge chamber channel such a configuration of the magnetic field which significantly increases the gradient of its radial component. This enabled to decrease the length of the ionization zone and the acceleration zone and, correspondingly, to reduce the length of the discharge chamber side walls contacting ionized operating gas, and to increase slightly focusing effect on the accelerated ion flow by the force lines of magnetic field that are more concave at the acceleration zone inlet.
However, like also in the above described accelerator, a maximal concentration of operating gas ions occurs in the center of the discharge chamber at the inlet into the acceleration zone; and radial electric fields caused by the difference of ion concentrations in the center of the discharge chamber and in the nean-the-wall areas force out a significant part of ions to the side walls of the discharge chamber. It is obvious that energy losses on the walls in the ionization zone of the discharge chamber will decrease with a reduction in the ratio of the surface area of the side walls to the plasma volume between these walls. However, the specified design embodiment of the discharge chamber does not permit to reduce this ratio.
Besides, it is possible to decrease the mass average divergence angle of the accelerated ion beam and to reduce the share of partially accelerated ions impacting the side walls of the discharge
REFERENCES:
patent: 5359258 (1994-10-01), Arkhipov et al.
patent: 5475354 (1995-12-01), Valentian et al.
Grishin S.D., Leskov L.V. "Elektricheskie paketnye dvigateli kowmicheskikh apparatov", 1989, Mashinostroenie (Moscow), p. 143.
Gopanchuk Vladimir
Sorokin Igor
O'Shea Sandra L.
Patel Vip
Societe Nationale Industrielle et Aerospatial
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