静电聚焦提升脉冲展宽分幅相机空间均匀性

Electrostatic focusing in the improvement of spatial uniformity of pulse-dilation framing camera

为提升脉冲展宽分幅相机的空间分辨均匀性,利用静电聚焦等位面均匀和像面漂移小的特性,采用静电透镜设计成像系统,构建脉冲展宽分幅相机电场分布和成像特性的关系,利用空间调制传递函数评估空间分辨率,并通过将空间分辨率的数值波动转换为梯度变化百分比的形式,对区域内的空间分辨率不均匀度进行定量描述.研究结果表明,等径双静电透镜成像系统能够增大探测区域,并降低空间分辨率不均匀度,满足脉冲展宽分幅相机向大面积探测的发展需求.在漂移区长度为400 mm,透镜孔径、轴向宽度和间距分别为200 mm、60 mm和210 mm的情况下,为避免电极电压过高引起的等位面均匀性变差和电子能量弥散增加,当第1和第2透镜电极分别加载-4.5 kV和10.0 kV电压时,脉冲展宽分幅相机的有效探测区域半径可达21 mm,离轴空间分辨率的波动范围为321.4~340.3μm,探测区域内的空间分辨率不均匀度为(1.11×10^(-4))%,均优于3磁透镜成像系统40.08~482.29μm的波动范围和0.027%的不均匀度.研究结论可为静电聚焦成像系统在脉冲展宽分幅相机中的应用提供理论基础,有助于量化并提升空间分辨率的均匀性.

To improve spatial resolution uniformity of pulse-dilation framing camera,the imaging system of the pulsedilation framing camera is designed using electrostatic lens,based on the characteristic of small image surface drift and homogeneous equipotential surface of the electrostatic focusing,the relation between the distribution of electric field and imaging characteristics is built,then the spatial resolution and the non-uniformity degree in the region are respectively estimated and quantitatively described by using the spatial modulation transfer function and converting the numerical fluctuation of spatial resolution into the form of gradient change percentage.The research results show that the detection area is increased and the non-uniformity degree is decreased using the imaging system of the double electrostatic lens with equal-diameter,which conforms to the development trend of large area detection.In the case,the length of drift region is 400 mm,the lens aperture,the axial width and the space between lenses are respectively 200 mm,60 mm and 210 mm,to avoid the deterioration of isoplane uniformity and the increase of electron energy dispersion caused by excessive electrode voltage,when the first and second lens electrodes are respectively-4.5 kV and 10.0 kV,the radius of the effective detection area for the pulse-dilation framing camera is 21 mm,the fluctuation range of the off-axis spatial resolution is 321.4~340.3μm,the spatial resolution nonuniformity degree is(1.11×10^(-4))%,which is superior to three magnetic lenses with the fluctuation range of 40.08~482.29μm and the non-uniformity degree of 0.027%.The study conclusion not only provides a theoretical basis for the feasibility of the imaging system of the electrostatic focusing in the pulse-dilation framing camera,but proposes a new idea to quantify and improve the spatial resolution uniformity.