The effect of an axial magnetic field(AMF) on an old xenon short-arc lamp is experimentally investigated in this work.As the AMF increases up to 18 mT,the visible radiation power and electric power ascend more than 80%and 70%respectively,and the radiation efficiency is improved by 23%for the best increment at 12 mT AMF.The measurement of radiation intensity shows that the increment of radiation intensity comes mostly from the plasma area close to the cathode tip,and partially from the other area of the arc column.Successive images of the arc indicate that the arc column not only rotates about its axis,but revolves around the axis of electrodes with the AMF.The arc column structure is constricted,distorted and elongated as the AMF increases.It is suggested that the improvements of the radiation intensity and radiation efficiency are attributed to the constriction of the arc column,which is mainly induced by the enhanced cathode jet.
Magnetically dispersed arc plasma [1] exhibits typically dispersed uniform arc column as well as diffusive cathode root [1,2] and diffusive anode root.In this paper magnetically dispersed arc plasma coupled with solid cathode is numerically simulated by the simplified cathode sheath model of LOWKE [3].The numerical simulation results in argon show that the maximum value of arc root current density on the cathode surface is 3.5×10 7 A/m 2,and the maximum value of energy flux on the cathode surface is 3×10 7 J/m 2,both values are less than the average values of a contracted arc,respectively.
A model coupling the plasma with a cathode body is applied in the simulation of the diffuse state of a magnetically rotating arc.Four parametric studies are performed:on the external axial magnetic field(AMF),on the cathode shape,on the total current and on the inlet gas velocity.The numerical results show that:the cathode attachment focuses in the center of the cathode tip with zero AMF and gradually shifts off the axis with the increase of AMF;a larger cathode conical angle corresponds to a cathode arc attachment farther away off axis;the maximum values of plasma temperature increase with the total current;the plasma column in front of the cathode tip expands more severely in the axial direction,with a higher inlet speed;the cathode arc attachment shrinks towards the tip as the inlet speed increases.The various results are supposed to be explained by the joint effect of coupled cathode surface heating and plasma rotating flow.
A generator of the gliding arc jet (GAJ), which is driven by a transverse magnetic field, is developed to produce non-equilibrium plasma at atmospheric pressure. The gas temperature is estimated using the spectrum of OH radicals to be about 2400±400 K. The determinations of electron temperature and electron density by using a line-ratio method are elaborated for the gliding arc jet plasma. This line-ratio method is based on a collisional-radiative model. The experiment results show that electron temperature is about 1.0 eV and electron density is about 6.9×1014 cm-3 . Obviously, the plasma of GAJ is in a non-equilibrium state.
