I have problems with cycle of the vacuum inside the sputtering chamber sometimes it runs a typical 30 minute cycle but other days it take more than an hour to finish the vacuum cycle. what factors could be influencing this?

Rudy - increased pump down cycles can be cause by a few different issues. My first thoughts are moisture in the chamber from ambient conditions. In other words, what is the humidity like during the longer pump down cycles? Also another though pops into my mind - if the chamber is left open (not under vacuum) for any length of time, that can increase the pump down cycle as well. One last thought, during the "long" pump down cycle, has anything different been introduced into the chamber that could be outgassing?

Of course not to be forgotten or ignored - a pesky leak that may occur on occasion when you open and/or close the chamber. Check the seal for nicks are particulates.

Regards - Daryl

thank you for your reply Daryl and reducing the time the chamber is open seem to help with this issue.