In high power impulse magnetron sputtering (HiPIMS) discharge, the cathode sheath is a particularly vital section which determines the spatial distribution of electric field and the energy and transport of charged particles. In this work, a single Langmuir probe is employed to explore the effects of dynamic cathode sheath on electron transport at the initial period of HiPIMS pulse. Measurements show that the electron temperature is as high as ~20 eV and the plasma density is much lower than ~10¹⁵–10¹⁶ m⁻³ at the beginning of HiPIMS pulse t < 3 μs; correspondingly, a feature of small low-energy amplitude and extended high-energy tail is found in the electron energy distribution function (EEDF). And the high-energy electrons can escape the magnetic trap and gradually diffuse to further axial positions, even to z = 140 mm with only several microseconds delay. The diffusion coefficient of electrons D_⊥ is larger than the typical Bohm diffusion at z > 32 mm in our discharge case. The two-dimension Particle-in-cell Monte Carlo collision (2D PIC-MCC) simulation results are well in agreement with the experimental results. The net positive charge density ∆n near the target is lower than ~+9.2×10¹⁴ m⁻³ at t = 0.5 μs, and the charge separation is up to ~0.4. In this case, the cathode sheath has a large thickness and the axial electric field E_Z outside the sheath is as strong as dozens of 10 kVm⁻¹. The simulation results confirm, for the case of the expanding sheath, (i) the electrons can be accelerated and escape the magnetic trap with weak constraint; (ii) the electron group can maintain their kinetic energy when they diffuse from the ionization region (IR) to bulk plasma (BP). When the net charge density increases to ~+3×10¹⁶ m⁻³ at t = 2.5 μs, the sheath thickness is condensed to ~1 mm with ~600 V voltage drop.

在大功率脉冲磁控溅射（HiPIMS）放电中，阴极护套是至关重要的部分，它决定了电场的空间分布以及能量和带电粒子的传输。在这项工作中，使用单个Langmuir探针来探索动态阴极护套对HiPIMS脉冲初始阶段的电子传输的影响。测量表明，在HiPIMS脉冲t的开始，电子温度高达〜20 eV，等离子体密度远低于〜10 ¹⁵ –10 ¹⁶  m ^-3 <3μs; 相应地，在电子能量分布函数（EEDF）中发现了低能量振幅小和高能量尾巴扩展的特征。高能电子可以逃脱磁阱，并逐渐扩散到其他轴向位置，甚至到z  = 140 mm时也只有几微秒的延迟。电子的扩散系数d _⊥是比在典型的玻姆扩散较大Ž  >32毫米在我们的情况下放电。二维单元格粒子蒙特卡洛碰撞（2D PIC-MCC）仿真结果与实验结果吻合良好。净正电荷密度的Δn接近目标比〜+ 9.2×10下¹⁴ 米^-3在t  = 0.5μs，电荷分离达到〜0.4。在这种情况下，阴极护套的厚度较大，并且护套外部的轴向电场E _Z高达几十个10 kVm ^-1。仿真结果证实，对于膨胀鞘的情况，（i）电子可以被加速并以弱约束逃逸到磁阱中；（ii）当电子基团从电离区域（IR）扩散到体等离子体（BP）时，它们可以保持其动能。当t  = 2.5μs时净电荷密度增加到〜+ 3×10 ¹⁶  m ^-3时，随着〜600 V电压降，鞘层厚度凝结为〜1 mm。