The heart of the GIF is its magnetic prism. Although complex, the fine adjustments of this multipole system are fully automated via the Tune GIF function of the Gatan Microscopy Suite ® (GMS) software. Sophisticated multipole optical elements (e.g., deflectors, quadrupoles, sextupoles) pre-shape the beam to compensate for the residual focus errors of the GIF prism. Use this solely for automated tuning and alignment of your GIF. Finally, there is a special mask aperture with a precision fabricated square array of holes. Apertures also control the collection angle and signal intensity in electron energy loss spectroscopy (EELS) experiments. There is also the option for a 1 mm aperture for high-resolution Continuum systems. The smallest of these apertures cut out the portion of the electron beam that contributes to small residual aberrations of the GIF prism focus (see below) and thereby helps achieve the best possible energy resolution in the electron energy loss spectra. The smaller apertures (2.5 and 5 mm, round) are useful for spectroscopy applications. Imaging apertures for the GIF Quantum and Continuum are square and are not useable for spectroscopy. This aperture and the TEM magnification fully determine the specimen field of view the GIF will capture. The largest entrance aperture (5 mm – GIF Quantum ® SE, 9 mm – GIF Quantum ER system and GIF Continuum™) you can use for all GIF imaging applications. Each GIF has four entrance apertures that are selectable under pneumatic control. The GIF entrance aperture determines what portion of the TEM beam will contribute to EFTEM images and electron energy loss spectra.
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