Low-Temperature Annealing of CdZnTeSe under Bias

We performed a gradual low-temperature annealing up to 360 K on a CdZnTeSe radiation detector equipped with gold and indium electrodes under bias at both polarities. We observed significant changes in the detector’s resistance and space-charge accumulation. This could potentially lead to the control and improvement of the electronic properties of the detector because the changes are accompanied with the reduction in the bulk dark current and surface leakage current. In this article, we present the results of a detailed study of the internal electric field and conductivity changes in CdZnTeSe detector for various annealing steps under bias taking into account different polarities during annealing and subsequent characterization. We observed that low-temperature annealing results in an increase in the barrier height at the contacts that, in general, reduces the dark current and decreases the positive space charge present in the sample compared to the pre-annealed condition.

EMERGING TRENDS IN WALL-FREE HALL THRUSTERS DEVELOPMENT

2D-hybrid model was created for the proposed new type accelerator with a virtual cathode which allows to avoid sputtering of the cathode surface and to preserve the dynamics of accelerated ions. In the framework of the model, it was shown that ions first form a positive space charge in the system center, and eventually, under an ac-tion of created own electric field, emerge from both ends of the system.

Revisiting the theory of positive glow corona with a comprehensive kinetic scheme

The theory of positive glow corona is revisited by performing a detailed simulation based on the fluid model with a comprehensive kinetic scheme (CKS). The kinetic scheme includes 28 species, 127 chemical reactions for N2/O2 mixture. The simulation results are compared with that from an averaged kinetic scheme (AKS) which considers only 5 species and 7 reactions. The two models give similar predictions in terms of discharge current. However, several differences in details of the results bring new physical insights to the theory of positive glow corona. It is shown that, the model with the AKS underestimates the detachment effect that plays an important role in positive glow corona discharge. Moreover, the wave-front of the current pulse calculated by the model with the CKS has a smaller steepness, a lower peak-to-peak value, and a longer rise time. These results are in better agreement with the experimental measurement reported in the literature. It is also found that the positive space charge of glow corona is dominated by O2+ in the ionization layer and by O4+ in the drift region far away from the anode. Negative ions are produced in the ionization layer close to the anode and the main species are O﹣and O3﹣.

Variation of Velocity of Ions in a Magnetized Plasma Sheath for Different Magnetic Field

The kinetic trajectory simulation method has been used to study ion velocity profile in a plasma sheath for varying magnetic field at fixed obliqueness. As the electrons have higher velocity compared to that of ions the wall is charged up negatively with respect to the core plasma. The negative potential then attracts the ions and repels electrons forming a thin positive space charge region in front of the wall. This positive space charge region, known as the ‘sheath’ separates the negatively charged wall from the quasineutral ‘presheath’ plasma. The ions moving towards the wall have to satisfy the Bohm criterion to ensure the stability of the overall plasma. The mean value as well as oscillation frequency of velocity of ions change as the magnetic field is varied from 1.5 to 10.5 mT. The maximum amplitude of normal component of velocity is almost independent of the magnetic field but the maximum amplitude of other components of velocity change and shows oscillating nature as the magnetic field changes.