Phase transition and charge transport through a triple dot device beyond the Kondo regime

Semiconductor quantum dot structure provides a promising basis for quantum information processing, within which to reveal the quantum phase and charge transport is one of the most important issues. In this paper, by means of the numerical renormalization group technique, we study the quantum phase transition and the charge transport for a parallel triple dot device in the strongly correlated limit, focusing on the effect of inter-dot hopping t beyond the Kondo regime. We find the quantum behaviors depend closely on the initial electron number on the dots, and the present model may map to single,double, and side-coupled impurity models in different parameter spaces. An orbital spin-1/2 Kondo effect between the conduction leads and the bonding orbital, and several magnetic-frustration phases are demonstrated when t is adjusted to different regimes. To understand these phenomena, a canonical transformation of the energy levels is given, and important physical quantities with respect to increasing t and necessary theoretical discussions are shown.

Fatigue behaviors and damage mechanisms for Nb_(3)Sn triple-helical structure at liquid nitrogen temperature

Nb_(3)Sn triple‐helical structure is the elementary structure in the superconducting cable of ITER magnets and undergoes prolonged fatigue loading in extreme environments leading to serious damage degradation.In this paper,the fatigue behaviors of the Nb_(3)Sn triple‐helical structure have been investigated by the strain cycling fatigue experiments at liquid nitrogen temperature.The results indicate that Nb_(3)Sn triple‐helical structures with short twist‐pitches possess excellent fatigue damage resistance than that of long twist‐pitches,such as longer fatigue life,slower damage degradation,and smaller energy dissipation.Meanwhile,a theoretical model of damage evolution has been established to reveal the effects of twist‐pitches on fatigue properties for triplehelical structures,which is also validated by the present experimental data.Furthermore,one can see that the Nb_(3)Sn superconducting wires in a triple‐helical structure with the shorter twist‐pitches have a larger elongation of helical structure and less cyclic deformation,which can be considered as the main mechanism of better fatigue damage properties for the triple‐helical structures during the strain cycling processes.These findings provide a better understanding of the fatigue properties and damage mechanisms for Nb_(3)Sn triple‐helical structures in superconducting cables of ITER magnets.

Study on the plasma generation characteristics of an induction-triggered coaxial pulsed plasma thruster

At present,spark plugs are used to trigger discharge in pulsed plasma thrusters（PPT）,which are known to be life-limiting components due to plasma corrosion and carbon deposition.A strong electric field could be formed in a cathode triple junction（CTJ） to achieve a trigger function under vacuum conditions.We propose an induction-triggered electrode structure on the basis of the CTJ trigger principle.The induction-triggered electrode structure could increase the electric field strength of the CTJ without changing the voltage between electrodes,contributing to a reduction in the electrode breakdown voltage.Additionally,it can maintain the plasma generation effect when the breakdown voltage is reduced in the discharge experiments.The induction-triggered electrode structure could ensure an effective trigger when the ablation distance of Teflon increases,and the magnetic field produced by the discharge current could further improve the plasma density and propagation velocity.The induction-triggered coaxial PPT we propose has a simplified trigger structure,and it is an effective attempt to optimize the micro-satellite thruster.