The Vacuum Generators cryotransfer sample stage was found to be mechanically and thermally stable at temperatures below -1750 C, and provides a very clean specimen environment under these conditions: no significant ice contamination was found to be present at low temperatures. Tests were carried out demonstrating the feasibility of imaging hydrated ice-embedded microtubule and virus preparations. The Tracor Northern ultrithin window x-ray detector was shown to detect the light elements (boron, carbon, nitrogen, oxygen and fluorine) although the peak shapes were complicated by effects of the pulse processor. The solid angle of 0.18 steradians subtended by the EDXS detector yielded a strong spectral signal from a test sample of freeze-dried cryosections of isolated nerve terminals (synaptosomes). The Gatan parallel-detection electron energy loss spectrometer was interfaced to the HB501 after modifications had been made to allow for a high temperature bake-out. In addition an extra ion pump was added for ultrahigh vacuum compatibility. The spectrometer energy resolution was demonstrated to be 0.35 electron-volts, as limited by the energy width of the field-emission distribution. A PC-AT computer system was employed to obtain parallel electron energy loss maps from ferritin molecules to demonstrate the capability of high spatial resolution microanalysis in the STEM.
