Generation of cold electrons in the downstream region of a microwave plasma source with near boundary resonances for production of negative ions

Sahu, Debaprasad; Bhattacharjee, Sudeep; Bandyopadhyay, M.; Chakraborty, Arun

doi:10.1007/s12648-011-0201-9

Cited by 3 publications

(1 citation statement)

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“…13 As another option, microwaves have been employed to generate high density plasmas by resonance heating mechanisms in presence of magnetic fields. [14][15][16][17] The discharge is electrodeless, clean and a stable plasma can be obtained, with possibilities for higher currents. Due to these advantages, there are several ongoing researches worldwide to develop microwave-driven negative ion sources, [18][19][20][21][22][23][24][25] such as the 2.45 GHz ion source at CEA (Sacley) which relies on parallel (k jj B) launching of waves along an axial magnetic field, 19 where the right and left circularly polarized waves can arise, and the Ecole Polytechnique source where the waves are launched using antennas.…”

Section: Introductionmentioning

confidence: 99%

Utilizing upper hybrid resonance for high density plasma production and negative ion generation in a downstream region

Sahu¹,

Bhattacharjee²

2012

Journal of Applied Physics

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Localized wave-induced resonances are created by microwaves launched directly into a multicusp (MC) plasma device in the k ⊥ B mode, where k is the wave vector and B is the static magnetic field. The resonance zone is identified as upper hybrid resonance (UHR), and lies r = ∼22 mm away from the MC boundary. Measurement of radial wave electric field intensity confirms the right hand cutoff of the wave (r = 22.5–32.1 mm) located near the UHR zone. A sharp rise in the corresponding electron temperature in the resonance region by ∼13 eV from its value away from resonance at r = 0, is favorable for the generation of vibrationally excited molecules of hydrogen. A transverse magnetic filter allows cold electrons (∼1–2 eV) to pass into the downstream region where they generate negative ions by dissociative attachment. Measurements of electron energy distribution function (EEDF) support the viewpoint. H− current density of ∼0.26 mA/cm2 is obtained at a wave power density of ∼3 W/cm2 at 2.0 mTorr pressure, which agrees reasonably well with results obtained from a steady state model using particle balance equations.

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