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Theoretical model o f the cathode region of a short glow discharge is presented, based on the concept developed in [ 11. According to the model, the cathode region is separated in three zones: the cathode voltage fall (CF), the negative glow (NG) and the Faraday dark space (FDS). Three groups of electrons are considered, fast, intermediate and trapped. The fast electrons are described by the continuous-energy-loss approximation, the electron impact ionization and attachment being the corresponding sources and losses. The spatial distributions of charged particles
The analysis of ion energy dependence on disruptive v o l t a g e ( w i t h direct current of electron b e a m E,) i n condition of working gas leak-in into the vacuum chamber demonstrated that t h e g r o w i n g of energy o f p r i m a r y electron beam E, caused the proportional growth of E; on the collector up t o the value of E; = 25 e V which stood unchanged with following rise of E,. S u c h b e h a v i o r o f E; can b e e x p l a i n e d so t h a t E;depends on the potential of the isolated collector Vc0/ determined by the balance between electron I, and ion I; currents. The growth of E, causes the growth of plasma density that leads t o the increase of 'discharging' Ii with constant 'charging' I , . That leads to reducing of Vmaxand E; correspondantly.T h e g a s leak-in i n t o t h e area of e l e c t r o n s o u r c e eliminates the reduce of E; with growth of E, and leads to proportional dependence between E; and E, in the whole using range of disruptive currents and voltages. The absence of E; reducing i n the investigated case can be explained b y t h e l o w e r plasma concentration at t h e expense of lower pressure. The b e a m s of t h a t k i n d m a y abe u s e d i n v a r i o u s branches of science and industry, including the synthesis o f c o a t i n g s o f d i f f e r e n t c h e m i c a l c o m p o s i t i o n , i o n implantation, etc.The source of negative ions has been elaborated on the basis of the low pressure beam-plasma discharge. Negative ions are generated by electron-atom interaction (A + e -+ A-) i d extracted across the magnetic field. The high concentration of low energetic electrons is reached with the help of secondary electron-electron emission by interaction of the primary rita-I.irsnary electron beam with target made of materials with high secondary emission rate. Secondary emission electrons i accumulating in electromagnetic trap like Penning cell with plug profile magnetic field.We have discovered that there are two operating coridih a s ob the negative ion source that depend upon the comelation of discharge characteristics. Under where 7 -secondary emission rate of target material, npdensity of plasma, nb -density of primary electron beam, T, -temperature of plaama el~ectrons, fb -energy of primary electron beam, U -potentid difference between plasma and target, double e1ectri.c layer is formed near the target surface, it cut off or restrict the stream of secondary emission electrons in electromagnetic trap. Thi3 effect is especially displayed under low pressures in the quasi-neutral condition of the primary electron beam transportation toward the target na z q. Under these conditions h e dendy of the low energetic electrons in the electromagnetk trap isn't higher than 10' ~m -~.During the oppmite correlation of the discharge characteristic, for example in the regime of plasma-beam discharge (nb < np) the restriction of th-emission is absent and the boundary layer near t~arget is the ion layer of the space charge. The high density of low-energetic electrons (-10" cm...
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