{HEAD ~ The portion} of {TAIL ~ tube} 12 near its external walls is maintained at a temperature at least 100 degrees C. below that of the alkali metal in tube 14 by means such as thermal exchange with ambient temperature air or other coolant fluids 
of
{ HEAD ~ The portion } of { TAIL ~ tube } 12 near its external walls is maintained at a temperature at least 100 degrees C. below that of the alkali metal in tube 14 by means such as thermal exchange with ambient temperature air or other coolant fluids
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH