You can use a timer to call self.close() for this, that is triggered when the popup window first loads. Add onLoad="setTimeout('self.close()',5000)" to the body tag of the page in the popup window, like this:
The 5000 is the time interval, in milliseconds. (1000 milliseconds is 1 second). Change that figure to set the amount of time you want the window to remain open after it loads.