{HEAD ~ A flange member} is provided on {TAIL ~ an outer wall} of the vacuum chamber to cover an opening in the wall 
is provided on
{ HEAD ~ A flange member } is provided on { TAIL ~ an outer wall } of the vacuum chamber to cover an opening in the wall
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH