Temporal evolution of collisionless sheaths
An experimental study was performed to determine the temporal evolution of Langmuir sheaths near an electrode to which a negative step bias is applied in a collisionless argon plasma. The plasma was produced by a hot-filament discharge in a multi-dipole device, with typical plasma parameters of P{sub 0} {approximately} 1 {times} 10{sup {minus}4} Torr (argon), n{sub e} {approximately} 1 {times} 10{sup 9} cm{sup {minus}3}, T{sub c} {approximately} 3 eV, and T{sub i} {approximately} 0.2 eV. Plasma potential data were obtained using emissive probes with two different techniques - time-resolved sampling and time-averaged techniques. The sheath is found initially to form close to the electrode, to extend to a maximum separation approximately with the speed of ion-acoustic wave, and to contract rather slowly to a steady-state value. The time scale required to reach a steady state is found to be close to the time scale of the presheath relaxation, which scales approximately as the plasma dimension divided by the ion-acoustic speed in the plasma. Characteristics of sheaths in rf plasmas are also measured using a parallel plate plasma capacitor placed in the multi-dipole device. It is observed that the plasma potential profile has significant variation with frequency, even for frequencies as low as 1 kHz which are far below the ion plasma frequency ({approximately} 1 MHz).
- Research Organization:
- Wisconsin Univ., Madison, WI (USA)
- OSTI ID:
- 7057886
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
Similar Records
Ion sheath dynamics in a plasma for plasma-based ion implantation
The magnetic presheath in the plasma-wall transition
Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ARGON
COLLISIONLESS PLASMA
PLASMA SHEATH
ELECTRIC DISCHARGES
FREQUENCY DEPENDENCE
ION ACOUSTIC WAVES
PLASMA POTENTIAL
TIME DEPENDENCE
ELECTRIC POTENTIAL
ELEMENTS
FLUIDS
GASES
ION WAVES
NONMETALS
PLASMA
PLASMA WAVES
RARE GASES
640410* - Fluid Physics- General Fluid Dynamics
700103 - Fusion Energy- Plasma Research- Kinetics