The chamber 150 also includes a wall portion that is disposed along {HEAD ~ a direction} that is substantially perpendicular to {TAIL ~ the direction} of channel wall 145 
is substantially perpendicular to
The chamber 150 also includes a wall portion that is disposed along { HEAD ~ a direction } that is substantially perpendicular to { TAIL ~ the direction } of channel wall 145
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH