{HEAD ~ The next step} is pumping down the plasma cleaning chamber interior region down to a pre determined pressure, with {TAIL ~ hydrogen} as the ambient gas 
is pumping with
{ HEAD ~ The next step } is pumping down the plasma cleaning chamber interior region down to a pre determined pressure , with { TAIL ~ hydrogen } as the ambient gas
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH