Experiments with Dipole and Monopole Lenses for an SEM

众所周知，在低电压（如1kv）下操作扫描电子显微镜是非常理想的。这是因为在低电压下，入射电子对试样的穿透很小，任何试样的损伤都局限于表层。然而，由于色差的影响，使用低电压会降低可用的分辨率。避免这个问题的唯一可行的方法是使用焦距非常短的镜头，但对于传统设计的镜头来说，这是不可行的。这一建议将支持原型显微镜的继续发展，其中新设计的透镜已放置在标本下方。这使得非常短焦距的镜头成为可能。从理论上讲，这一发展将使显微镜的分辨能力比目前可用的任何仪器提高两倍，甚至三倍。本提案所要求的资金将用于改进原型显微镜，并使用具有良好特征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.