The aluminium foil membrane has a mylar™ backing which enables {HEAD ~ the foil} to withstand {TAIL ~ the pressure difference} across it due to the gaseous environment outside the chamber and the substantial vacuum within 
The aluminium foil membrane has a mylar ™ backing which enables { HEAD ~ the foil } to withstand { TAIL ~ the pressure difference } across it due to the gaseous environment outside the chamber and the substantial vacuum within
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH