Aperture Holders

The JEOL JEM 1010 has three apertures that the user can change: apertures for the condenser lens (CL), the objective lens (OL) and the intermediate lens (IL, also often called SAA - selected area apertures). The basic design of the aperture holders is the same in all three cases, and is shown in detail in the line drawing to the right.

An aperture strip contains the actual apertures (holes in a thin metal piece) and is extended into the path of the electrons by flipping the lever shown in the photograph of the IL (SAA) aperture holder below: when the lever points to the right, no aperture is inserted, and when it points to the left, an aperture is in place. The individual apertures are selected by turning the large knurled knob (marked in the line drawing), and can be centered using the knob to the right of the large knob and the smaller knob at the end of the large knurled knob (both marked in the line drawing). As shown in the photograph, the relative size of the different apertures is shown by the size of the white dots on the large knurled knob, and the chosen aperture is the one closest to the black dot near where the lever pivots.

In general, users should not need to adjust the CL aperture. However, use of the smallest available CL aperture can make the electron beam a bit more coherent and can lead to better images. The cost of a smaller CL aperture is that the brightness of the beam drops considerably, and the use of the smallest aperture may only be worthwhile when recording images at relatively low magnifications (< 10,000x). If the CL aperture is changed, it will need to be re-centered (and the OL aperture must be removed to do this).

The IL (SAA) aperture is normally only used when recording electron diffraction. Users should talk to the Electron Microscopy Center (EMC) staff about all electron diffraction work before doing anything with the 1010.

The OL aperture will be taken out fairly frequently (e.g., when searching a grid in low mag mode) and should be centered whenever it is reinserted into the beam path. The smallest OL aperture will produce the highest contrast images, but at the cost of resolution in the images. This may not be a concern to most users, but they should be aware of this trade-off.

Please talk to the staff about how to remove, insert and center both the CL and OL apertures before attempting anything on your own.