SEM/STEM detectors and CRTs


Posted on Feb 5, 2014

The TEM that we have, the Jeol 2000fx is equipped with two extra detectors, one secondary electron detector, i. e. SEM imaging, as well as a STEM detector at the bottom of the microscope. Because the system are from the 80`s the imaging from these detectors is (read `was`)accomplishedby using photographic film to copy the image shown on the CRT. An


SEM/STEM detectors and CRTs
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extra CRT monitorspecificallyused for this task is located in a free standing box in which the camera with light sensitiv polaroid film is attached to. Nowadays, everything is digital, and polaroid imaging is therefore not very user friendly or timesaving. Besides, one of the two CRT`s used for setting upp the image to be captured is broke in our system and the other one is almost burned out. -Time to move into the nextcenturyof technology. By different means I found out that the ASID panel, i. e the one thatcontrolsthe scanning of the electron beam during SEM/STEM imaging, has a extra contact hidden behind the backpanel, labeled SG6, figure 1. Figure 1, After opening the back-panel of the ASID unit the signal generator card (SG) is somewhat exposed as well as the extra contact SG6, used for external scan control. If one looks at thecircuitdiagram, figure 2, one can se that the external scan mode is activated by connecting pin 5 of the SG6 to ground. This mode bypass the scan generator function of the ASID panel and allows you to insert your own scan signals at pin 1 and 2 for horisontal and vertical. The signal level happens to be ±10 Volts and this is lucky thus the PXI-6229 card that I use for this task also has this amplitude range limit. To connect to the SG6 I assembled a signal cable from SG6 internally to the front of the ASID, a switch was used to connect pin 5 to ground, and the horisontal and vertical scan...




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