脉冲展宽分幅变像管的最优成像磁场研究

Optimal Imaging Magnetic Field of Pulse-Dilation Framing Image Converter Tube

磁聚焦脉冲展宽分幅变像管是时间分辨率优于10 ps的超快诊断设备,其空间分辨率与成像磁场密切相关。为讨论该问题,建立了脉冲展宽分幅变像管模型,在不同半径发射区域成像磁场下,采用瑞利判据对点成像分布计算空间分辨率,并基于轴上最优和物点间差异最小原则,分析最优成像磁场。研究结果表明,在单磁透镜脉冲展宽分幅变像管中,整体空间分辨率不随磁场增大或减小而变好,而是存在一个特定发射区域对应的成像磁场,使其达到最优。当透镜孔径为160 mm、漏磁缝隙为4 mm、轴向宽度为100 mm、漂移区为500 mm和电子发射能量为3 keV时,8 mm半径区域的成像磁场为最优,其轴上最大磁场为37.87×10^(-4) T。在微通道板空间分辨率为55μm和缩小1倍成像的情况下,物面0、5、10、15 mm位置的空间分辨率分别为29.86、43.08、87.07、276.88μm,模拟计算结果与已测数据基本吻合。研究结论为建立成像磁场和整体空间分辨率之间的联系及最优化空间分辨率的模拟计算提供了一种具有参考性的方法。

The magnetically focused pulse-dilation framing image converter tube is an ultrafast diagnosis device with a temporal resolution within 10 ps and a spatial resolution that closely relates to the imaging magnetic field. In this study, a model of a pulse-dilation framing image converter tube was constructed and the spatial resolution of the point imaging distribution was calculated under the Rayleigh criterion. The imaging magnetic field was applied with emission areas of different radii, and the imaging magnetic field was optimized by finding the optimal on-axis and minimum difference between object points. In the pulse-dilation framing image converter tube with a magnetic lens, the overall spatial resolution was not improved by increasing or decreasing the magnetic field, but was optimized by the magnetic field of the specific emission area. When the lens aperture is 160 mm, the slit width is 4 mm, the axial width is 100 mm, the drift area is 500 mm, and the emission energy is 3 keV, the imaging magnetic field is optimized by setting the emission area radius to8 mm and the maximum magnetic field along the axis to 37. 87 × 10^(−4) Tesla. As the spatial resolution of the microchannel plate is 55 μm and the imaging is 1∶ 2, the spatial resolutions are 29. 86 μm, 43. 08 μm, 87. 07 μm, and 276. 88 μm at locations of 0 mm, 5 mm, 10 mm, and 15 mm on the object plane, respectively. The simulation results are consistent with the measured data. This work provides a reference method for establishing the relationship between the imaging magnetic field and overall spatial resolution and for optimizing the calculations of the spatial resolution simulation.