Numerical study of the effect of aft-loaded magnetic field on multiple ionizations in Hall thruster

It is assumed that the shift of a strong magnetic field region with a positive gradient from exit plane to outside, namely the transit from a normal loaded magnetic field to an aft-loaded one, enhances the multiple ionization process in the magnetically shielded Hall thruster. To confirm this conjecture, a comparative study is carried out numerically with a particle-in-cell method. The simulation results prove that compared with the normal loaded magnetic field, the application of aft-loaded magnetic field enhances the multiple ionization process. This study further analyzes the ionization characteristics of the transition from low-charged ions to high-charged ions under two magnetic field conditions and the influence of the magnetic strength of aft-loaded magnetic field on the multiple ionization characteristics. The study described herein is useful for understanding the discharge characteristics of Hall thruster with an aft-loaded magnetic field.

Simultaneous achievement of large electrocaloric effect and ultrawide operating temperature range in BaTiO_(3)-based lead-free ceramic

The electrocaloric effect(ECE),known for its environmentally friendly characteristics,holds significant promise for advancing next-generation solid-state refrigeration technologies.Achieving a large ECE along with a wide working temperature range near room temperature remains a key developmental goal.In this study,we successfully obtained a substantial ECE of 1.78 K and an extensive working temperature range of 103 K(AT>1.52 K)near room temperature in CaZrO_(3)-modified BaTiO_(3) lead-free ferroelectric ceramics.Furthermore,this achievement was verified using direct methods.The piezoresponse force microscopy(PFM)results suggest that the broad temperature range is attributed to the formation of ferroelectric microdomains and polar nanoregions(PNRs).Furthermore,X-ray photoelectron spectroscopy(XPS)and ultraviolet-visible(UV-Vis)spectroscopy reveal a decrease in the oxygen vacancy concentration and an increase in the bandgap for higher CaZrO_(3) doping levels.These changes synergistically enhance the maximum applied electric field,helping to achieve a high-performance EcE near room temperature.This research presents a straightforward and effective approach for achieving high-performance ECEs in BaTiOg lead-free ceramics,offering promising prospects for application in next-generation solid-state refrigeration technologies.