Experiments with Dipole and Monopole Lenses for an SEM

众所周知，非常希望在诸如1kV的低电压下操作扫描电子显微镜。 这是由于在低电压下，入射电子穿透到样品中的程度很小，并且任何样品损坏都仅限于表面层。然而，由于色差效应，低电压的使用降低了可用的分辨率。避免这个问题的唯一可行的方法是使用焦距很短的透镜，但是对于传统设计的透镜，这是不可行的。这项建议将支持原型显微镜的持续发展，其中新设计的透镜已被放置在标本下方。这使得非常短焦距的镜头成为可能。从理论上讲，这一发展应提高显微镜的分辨率两个，甚至三个，任何仪器，目前可用的倍。本提案中要求的资金将用于改进原型显微镜，并使用特征明确的生物标本证明其有用性。

It is well known that it is highly desirable to operate scanning electron microscopes at low voltages such as 1 kV. This is due to the fact that at low voltages penetration of the incident electrons into the specimen is small and any specimen damage is restricted to the surface layer. However, the use of low voltages reduces the available resolution due to chromatic aberration effects. The only practical way to avoid this problem is to use lenses of very short focal length, but with a lens of conventional design this is not feasible. This proposal will support continuing development of a prototype microscope in which the lens of new design has been placed below the specimen. This makes lenses of very short focal lengths feasible. Theoretically this development should improve the resolving power of the microscope two, or even three, times over any instrument that is currently available. The funds requested in this proposal will be used both to refine the prototype microscope and demonstrate its usefulness using well-characterized biological specimens.