Wikipedia lists some other modern uses including (most unexpectedly) in particle accelerators: http://en.wikipedia.org/wiki/Vacuum_tube#Vacuum_tubes_in_the_21s

Wikipedia lists some other modern uses including (most unexpectedly) in particle accelerators: http://en.wikipedia.org/wiki/Vacuum_tube#Vacuum_tubes_in_the_21st_century http://en.wikipedia.org/wiki/Vacuum_tube#Vacuum_tubes_in_the...