Abstract
For the Philips CM30 (or earlier EM430), the large surface area in the gun, the relatively poor pumping speed at the base of the gun, and the use of the same 100 l/s ion getter pump (IGP) for the column and gun, all lead to a significant degradation of gun vacuum (and slow recovery) following the gas burst involved in specimen exchange, even with extended pumping in the airlock. Since the vacuum quality in the gun is important for LaB6 filament life and high voltage stability, we adopted a conservative approach to the maximum pressure Pc allowed for the application of high voltage or filament emission; we chose an IGP reading of 22 (5 × 10−5 Pa). Delays of ~15 min typically occurred following specimen insertion. To avoid these problems the vacuum system has been modified. The goals were threefold: (1) To increase the pumping speed at the gun. The conductance of the original 600-mm-long vacuum line with three 90° elbows and a valve (V5) results in a pumping speed of < 10 l/s at the base of the emission chamber and a routine pressure of 3 × 10−5 Pa (1.5 × 10−7 torr).
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Proceedings, annual meeting, Electron Microscopy Society of America
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
