Effect Of Neutral Pressure Research Articles

Effect of neutral pressure on the blue core in Ar helicon plasma under an inhomogeneous magnetic field

The effect of neutral pressure on the blue core in Ar helicon plasma under an inhomogeneous magnetic field was investigated in this work. The neutral pressure was set to 0.08 Pa, 0.36 Pa, and 0.68 Pa. A Nikon camera, intensified charge-coupled device (ICCD), optical emission spectrometer (OES), and Langmuir probe were used to diagnose the blue core in helicon plasma. Helicon plasma discharges experienced density jumps from the E mode, H mode to W mode before power just rose to 200 W. The plasma density increased and maintained a central peak with the increase of neutral pressure. However, the brightness of the blue core gradually decreased. It is demonstrated that the relative intensity of Ar II spectral lines and the ionization rate in the central area were reduced. Radial electron temperature profiles were flattened and became hollow as neutral pressure increased. It is demonstrated that increasing the neutral pressure weakened the central heating efficiency dominated by the helicon wave and strengthened the edge heating efficiency governed by the TG wave and skin effect. Therefore, the present experiment successfully reveals how the neutral pressure affects the heating mechanism of helicon plasma in an inhomogeneous magnetic field.

Self-consistent global model with multi-step ionizations in inductively coupled plasmas

Modified particle and power balance equations including multi-step ionizations are derived and solved in a self-consistent manner. According to the modified balance equations, the electron temperature (Te) decreases with the electron density (ne) to balance between the generation and the loss of an electron-ion pair. The multi-step ionizations give rise to the decrease in the collisional energy loss per electron-ion pair created (εc) so that the electron density is rapidly increased compared to when only single step ionization is considered. The effect of neutral pressure on the multi-step ionizations is presented and discussed.

Theoretical Investigations on the Relation between Neutral Pressure and Beta in HANBIT Mirror Discharges

A numerical study is made of the effects of neutral pressure on the characteristics of HANBIT mirror plasmas. One-dimensional discharge simulations are carried out under various neutral pressure conditions and the dependence of β (=plasma pressure/magnetic pressure) on the neutral pressure P0 is investigated. It is found that β and ion temperature increase rapidly with decreasing pressure below P0 ~ 2 × 10-6 Torr in HANBIT mirror discharges.