1. :You don't need a particularly sturdy container to contain ultra high vacuum . 2. Older instruments may have used oil diffusion pumps for high vacuum regions. 3. Such pumps inexpensively and reliably produce extremely low pressures in ultra-high vacuum systems. 4. These metals are therefore relatively volatile, and are avoided in ultra-high vacuum systems. 5. In electron microscopy ( EM ), samples are imaged in an ultra-high vacuum . 6. High vacuum also eliminates oxidation that might occur in the presence of air.7. Dicoronylene sublimes under high vacuum , 0.001 torr, between 250 �C and 300 �C. 8. After preparation, it is usually purified by high temperature sublimation under high vacuum . 9. Ultra-high vacuum systems are usually made of stainless steel with metal-gasketed vacuum flanges. 10. Stopcock grease is always used in high vacuum applications to make the stopcock air-tight. 
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