- Story Ideas
- Send Corrections
Helium is an inert gas in the periodic table. It and hydrogen were abundant when the earth was formed but they have diffused into the atmosphere since, and there is now a concern about a “shortage” of helium in the future. Helium is used in blimps, balloons, special welding, research. Today, liquid helium is essential for MRI (magnetic resonance imaging).
Basic research on resonance imaging was done in the 1950s but Ray Damadian developed its use on humans in the 1970s. This required a magnetic field large enough to surround a human body. This size and power were not available using normal electromagnets. Damadian turned to superconducting magnets. The writer worked with Damadian at SUNY on superconducting alloys as produced by KBI, Boyertown, in the 1970s.
Superconductors are special alloys that have zero resistance to electron flow (DC electricity) at very low temperatures, near absolute zero, which is zero degrees Kelvin (minus 460 degrees F). Niobium titanium (NbTi) is used in today’s MRI equipment. It changes to superconducting at 11 degrees K. Liquid helium “boils” at 4 degrees K. The entire magnetic coil must be immersed in liquid helium. All MRI locations get frequent visits from their “helium man” — even Pottstown, usually in the wee hours, due to the special handling. The liquid helium is kept in special Dewar equipment similar to a thermos container.
Helium cannot be “made.” Its outer valence shell is full and stable and will not react, hence, “inert.” There is residual helium in some natural gas. A major source is in Amarillo, Texas (about 3 percent He). The helium is recovered from the gas by pressure and fractional distillation. There are other smaller natural gas sources in the Soviet.
As such, no helium, no MRI. Someday, other superconductors may work in liquid hydrogen at 18 degrees K — like vanadium-gallium, etc. — but not today. Maybe conservation is in order? Smaller balloons in the Macy Thanksgiving Day parade, etc. would help.