The third form is that the cathode has a heater so that {HEAD ~ the cathode temperature} is controlled in {TAIL ~ a range} of the room temperature to about 100 degrees Celsius to regulate an amount of electron emission from the cathode 
is controlled in
The third form is that the cathode has a heater so that { HEAD ~ the cathode temperature } is controlled in { TAIL ~ a range } of the room temperature to about 100 degrees Celsius to regulate an amount of electron emission from the cathode
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH