Computation Design to Simulate an Objective Magnetic Lens and Study of Effect the Distance Between Pole pieces on its Optical Properties

In this article, an objective magnetic lens was developed and its optical properties were analysed using simulation programs depending on finite elements method. Better optical properties, low values of electron probe diameter(dp) incident on specimen surface, spherical aberration (ds), chromatic aberration (dc), diffraction aberration (dd), Gaussian aberration (dg) and suitable aperture angle were achieved. Asymmetric double pole piece magnetic lens with good properties was designed. The effect of the different distances between pole pieces (S=2,4,6,8)mm, on the magnetic lens properties to achieve the best configuration for the lens was investigated. The results show that at constant excitation (NI=1 kA-t) and acceleration voltage (Vr=10 kV), distance (S=2 mm) was offered good optical properties; focal length (fo=4.04 mm), spherical aberration (Cs=3.75 mm), chromatic aberration (Cc=3.12 mm). The greatest axial magnetic flux (Bz=0.18 T) was obtained. The diameter of an electron probe as a function of aperture angle was investigated. According to the findings, an aperture angle of (=2 mrad) has improved optical properties (dp=12.24 mm), (ds=5.64 mm), (dc=0.0005 mm), (dd=4.06 mm), and (dg=10.06 mm). The L1 design was selected as the best design, and its optical properties were also investigated.

Keywords: electron microscope, objective magnetic lens, distance between pole piece

In this article, an objective magnetic lens was developed and its optical properties were analysed using simulation programs depending on finite elements method. Better optical properties, low values of electron probe diameter(dp) incident on specimen surface, spherical aberration (ds), chromatic aberration (dc), diffraction aberration (dd), Gaussian aberration (dg) and suitable aperture angle were achieved. Asymmetric double pole piece magnetic lens with good properties was designed. The effect of the different distances between pole pieces (S=2,4,6,8)mm, on the magnetic lens properties to achieve the best configuration for the lens was investigated. The results show that at constant excitation (NI=1 kA-t) and acceleration voltage (Vr=10 kV), distance (S=2 mm) was offered good optical properties; focal length (fo=4.04 mm), spherical aberration (Cs=3.75 mm), chromatic aberration (Cc=3.12 mm). The greatest axial magnetic flux (Bz=0.18 T) was obtained. The diameter of an electron probe as a function of aperture angle was investigated. According to the findings, an aperture angle of (=2 mrad) has improved optical properties (dp=12.24 mm), (ds=5.64 mm), (dc=0.0005 mm), (dd=4.06 mm), and (dg=10.06 mm). The L1 design was selected as the best design, and its optical properties were also investigated.

Anahtar Kelimeler: electron microscope, objective magnetic lens, distance between pole piece

Page Range: 67-76

Ahmed, M. J. & Hussein, M. A. (2022). Computation Design to Simulate an Objective Magnetic Lens and Study of Effect the Distance Between Pole pieces on its Optical Properties. Journal of Current Researches on Educational Studies, 12 (2), 67-76.