The systematic Langmuir probe measurements for a weakly magnetized plasma have been carried out in the Linear Magnetized Plasma Device for different magnetic fields. By comparing the ion current density of probes with...The systematic Langmuir probe measurements for a weakly magnetized plasma have been carried out in the Linear Magnetized Plasma Device for different magnetic fields. By comparing the ion current density of probes with different sizes, the sheath thickness can be evaluated. It is found that while the ratio of cylindrical probe's dimension to ion Larmor radius is not more than 2, the model of probe for non-magnetized plasma is still applicable.展开更多
In a magnetized plasma column generated from an electronegative gas, negative-ions accumulate around the plasma column via radial diffusion. In this study, a dc discharge is applied in SF6 gas to produce a plasma colu...In a magnetized plasma column generated from an electronegative gas, negative-ions accumulate around the plasma column via radial diffusion. In this study, a dc discharge is applied in SF6 gas to produce a plasma column, and the radial density profile of negative-ions is measured by Langmuir probes using the modified Bohm criterion. The gas pressure and discharge current dependences of negative-ion density are also measured. It is found that the negative-ion density of 8.0 × 1017 m-3 is obtained around the plasma column at r = 1.0 cm when SF6 pressure is 0.13 Pa and discharge current is 0.50 A. The negative-ion density has radial gradient, and the electron density is much lower in this region.展开更多
Volume negative ion production relies on a magnetic filter(MF),where the plasma downstream of the MF is characterized by a strip-like pattern that consists of a bright and dense plasma region.In this work,we study,in ...Volume negative ion production relies on a magnetic filter(MF),where the plasma downstream of the MF is characterized by a strip-like pattern that consists of a bright and dense plasma region.In this work,we study,in a radio-frequency plasma source,the effects of operating pressure on this strip.This investigation,conducted using a Langmuir probe,shows that the plasma uniformity might be controlled through the gas pressure.Moreover,the operating pressure determines on which hemi-cylinder(side of magnetic field lines)the strip forms.This side inversion of the high-density plasma hemi-cylinder is due to an inversion of an ambipolar electric field that changes the E?×?B drift direction.展开更多
基金The project supported by the National Nature Science Foundation of China (No.19975047, No.10075046)
文摘The systematic Langmuir probe measurements for a weakly magnetized plasma have been carried out in the Linear Magnetized Plasma Device for different magnetic fields. By comparing the ion current density of probes with different sizes, the sheath thickness can be evaluated. It is found that while the ratio of cylindrical probe's dimension to ion Larmor radius is not more than 2, the model of probe for non-magnetized plasma is still applicable.
文摘In a magnetized plasma column generated from an electronegative gas, negative-ions accumulate around the plasma column via radial diffusion. In this study, a dc discharge is applied in SF6 gas to produce a plasma column, and the radial density profile of negative-ions is measured by Langmuir probes using the modified Bohm criterion. The gas pressure and discharge current dependences of negative-ion density are also measured. It is found that the negative-ion density of 8.0 × 1017 m-3 is obtained around the plasma column at r = 1.0 cm when SF6 pressure is 0.13 Pa and discharge current is 0.50 A. The negative-ion density has radial gradient, and the electron density is much lower in this region.
文摘Volume negative ion production relies on a magnetic filter(MF),where the plasma downstream of the MF is characterized by a strip-like pattern that consists of a bright and dense plasma region.In this work,we study,in a radio-frequency plasma source,the effects of operating pressure on this strip.This investigation,conducted using a Langmuir probe,shows that the plasma uniformity might be controlled through the gas pressure.Moreover,the operating pressure determines on which hemi-cylinder(side of magnetic field lines)the strip forms.This side inversion of the high-density plasma hemi-cylinder is due to an inversion of an ambipolar electric field that changes the E?×?B drift direction.
