Why use niobium to make the cavities? Each one of Jefferson
Lab's 338 acceleration cavities cost about $30,000. A good
portion of this expense comes from the use of niobium, a
relatively rare and expensive metal. Why were the cavities made
from niobium when they could have been made from a less
expensive metal, such as copper? Most metals are good conductors
of electricity, but they aren't perfect. A property of metals,
known as resistance, opposes the flow of electrical currents and
converts electrical energy to heat. Unless the metal is part of
something that is suppose to get hot (an oven, toaster, space
heater or similar device), the heat is a waste product and adds
to the expense of operating the device. Jefferson Lab's cavities
work by moving charges back and forth over its surface. This
movement of charges is an electrical current. If Jefferson Lab's
cavities were made from copper, the cavities would heat, expand
and eventually melt. This would not be good for the accelerator.
There are two ways to avo