Influence of lens aperture size on spatial performance of short magnetic focusing framing camera

Abstract

In this work, a pulse-dilation framing camera with short magnetic focusing was studied. The magnetic field, electron trajectory and imaging distribution were simulated, the influence of magnetic lens aperture size on spatial performance was analyzed and improvements were discussed. The results show that the overall spatial performance was improved by enlarging the aperture and further improved by increasing the size of leakage magnetic slit, even if the spatial resolution of paraxial region became poorer. When the acceleration energy was 3 keV, leakage slit was 10 mm and aperture size was increased from 200 to 280 mm, the on-axis spatial resolution decreased from 92 to 130 μm, 45 mm off-axis spatial resolution improved from 618 and 456 μm and the coefficient of variable decreased from 0.59 to 0.40. Moreover, when the aperture was enlarged to 280 mm and leakage slit was increased to 40 mm, the on-axis spatial resolution, 45 mm off-axis spatial resolution, and coefficient of variable were 159 μm, 359 μm and 0.26, respectively. These results contribute towards further optimization of structural parameters of the short magnetic focusing system and provide design guidelines for achieving a pulse-dilation framing camera with detection area diameter of up to 90 mm(radius is 45 mm).