Morishita Shigeyuki, Sawada Hidetaka
JEOL Ltd., 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan.
JEOL USA Inc., 11 Dearborn Road, Peabody, MA 01960, USA.
Ultramicroscopy. 2022 Sep;239:113569. doi: 10.1016/j.ultramic.2022.113569. Epub 2022 Jun 6.
Spherical aberration correctors using hexapole fields are widely used and are pivotal in atomic-resolution imaging. Although hexapole-field correctors increase the aberration-free angular range, the angular range is limited by higher-order aberrations, such as six-fold astigmatism or sixth-order three-lobe aberration. Here, we propose two types of spherical aberration correctors to compensate for geometrical aberrations up to the sixth order. The first is a four-hexapole corrector, while the second is a two-hexapole corrector, where each hexapole has a nonuniform magnetic field. The four-hexapole corrector can increase the aberration-free angle up to almost 100 mrad. The two-hexapole corrector with a nonuniform magnetic field has a smaller aberration-free angle than that of the four-hexapole corrector, but it is more compact. The dominant residual aberration in these correctors is seventh-order spherical aberration or chaplet aberration, which is seventh-order geometrical aberration.
使用六极场的球差校正器被广泛应用，并且在原子分辨率成像中起着关键作用。尽管六极场校正器增加了无像差角范围，但该角范围受到诸如六重像散或六阶三叶像差等高阶像差的限制。在此，我们提出两种类型的球差校正器，以补偿高达六阶的几何像差。第一种是四极六极校正器，第二种是双六极校正器，其中每个六极具有非均匀磁场。四极六极校正器可将无像差角增加到几乎100毫弧度。具有非均匀磁场的双六极校正器的无像差角比四极六极校正器的小，但它更紧凑。这些校正器中的主要残余像差是七阶球差或小环像差，后者是七阶几何像差。
