帕申定律是气体放电领域最重要的定律之一，它可以很好地描述均匀电场中击穿电压Ub与气压和间隙距离乘积pd的U型曲线函数关系，但是它并不适用于非均匀电场的情况。很多学者在实验中发现随着平板间隙距离的增大，即使在相同pd的情况下，击穿电压也会升高，帕申曲线向上移动，可以称其为帕申曲线的分离现象。本文在前人基础上继续研究这个问题，通过实验研究了非均匀电场低气压空气间隙的击穿。 研究了绝缘套筒对于平行平板空气间隙帕申曲线的影响，设计并使用了带有凸台的平板电极。进行实验研究发现，在间隙距离d和电极的半径r保持不变的情况下，随着套筒半径R的缩小，击穿电压有所下降，通过在套筒的表面开槽增加爬电距离后进行的实验发现，套筒表面存在的沿面放电导致了击穿电压的降低。套筒改变了间隙原来的击穿特性，使得体击穿转变为沿面击穿。 研究了电场分布变化对于平行平板间隙帕申曲线的影响，实验中发现空气中在较低pd的情况下，随着间隙距离与电极半径之比d/r的增大，在pd保持不变时，击穿电压升高，对应帕申曲线上移，d/r和pd都保持不变时，帕申曲线几乎不发生分离，说明击穿电压可以表示为Ub= f (pd, d/r)。 进行实验研究了低气压空气中平行平板电极的间隙d相同而电极半径r不相同时，帕申曲线出现的分离现象。通过实验发现，在pd小于一定数值时，间隙距离d不变，增大d/r，电场分布越不均匀时击穿电压更高，此分离现象与实际经验存在“矛盾”。利用气体的数密度和碰撞时的动量传递截面可以估算放电时电子的平均自由程l，通过推导可以得到l与气压p的反比关系，据此关系可以解释这种“矛盾”的现象。 进行实验初步研究了棒-板间隙的帕申曲线，比较了两个几何尺寸相似的棒-板电极在棒电极直径不同时的帕申曲线。结合仿真模拟，通过理论推导，分析了棒-板间隙的电场分布。 进行了低气压平行平板电极辉光放电实验，拍摄了间隙的放电图像，对放电的图像进行分析，研究尺寸成比例，几何外形相似的平行平板间隙辉光放电时的光强分布。

Paschen’s law is one of the most significant law in the area of gas discharge. It can describe the U-shaped curve relation between breakdown voltage Ub and the product of pressure and gap distance well. However, it is now suitable for the conditions in the ununiform field. Many scholars found that as the gap distance increases, the breakdown voltage will raise though the pd stays constant as the corresponding Paschen’s curve move upward. This phenomenon can be called as the separation phenomenon of Paschen’s curves. This thesis aims to continue the research on this problem on the basis of previous studies and research the breakdown of air gaps at low-pressure in the ununiform field. This thesis explores how the dielectric tube may affect the Paschen’s curves of parallel electrodes in the low-pressure air. Based on the results of the experiments in which the gap length d and the electrode radius r remained constant, it was found that the smaller the tube radius R is, the lower the breakdown voltage is. After grooves were cut over the surface of the tube, experiments were carried out using the tubes with grooves and longer creeping distance. It was discovered that creeping discharge which happens on the surface of insulated tubes lead to lower the breakdown voltage. The tubes change the original breakdown characteristics of the gaps convert the breakdown of gap converts into flashover on the surface. This thesis research and analysis how the change of field distribution may affect the Paschen’s curves. When the pd is low and remain the same, the larger the ratio of the gap distance and electrode radius d/r is, the higher the breakdown voltage is and the upper the Paschen’s curve is. Moreover, when d/r and pd remain the same, the Paschen’s curve hardly changes. So Ub= f ( pd, d/r) can be used to describe the breakdown voltage. The experiments were performed to study the separation of Paschen’s curves as gap distance d remained constant and radius r of the electrode changed in the low-pressure air. The experiments show that, when the pd is lower than a certain value and d remains constant, the breakdown voltage rises with the increasing value of d/r and more ununiform field. This result seems to “contradict” with practical experience. The mean free path length of electron could be estimated with the number density of the gas and the momentum transfer cross section. By doing the theoretical estimation, the inverse relation of l and p can be found where l is the mean free path length of electron. This can be used to explain the “contradictable” phenomenon. Experiments were carried out to research the Paschen’s curves of bar-plane electrode comparing two bar-plane electrodes with the similar size and different diameters of bar electrodes. By carrying out the simulation, field distribution of the bar-plane electrode was analyzed from the theoretical perspective. Glow discharge experiments of plane electrodes in low-pressure were taken. Pictures of discharge gaps were taken. The pictures of discharge were analyzed. The research aimed to study the distribution of luminous intensity of parallel electrodes with proportional size and similar shapes.