{HEAD ~ a pressure vessel} surrounding {TAIL ~ the outside wall} of the reaction chamber, thus forming a first annulus 
surrounding
{ HEAD ~ a pressure vessel } surrounding { TAIL ~ the outside wall } of the reaction chamber , thus forming a first annulus
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH