Superconductivity
Helium is required to create superconductivity. Superconductivity is a characteristic of some conductors to have zero electrical resistance when they are cooled below their critical temperature.
Magnetic Resonance Imaging (MRI)
Magnetic Resonance Imaging is used for medical diagnosis and requires superconducting magnets. Without helium, superconductivity cannot be achieved and MRIs will not be possible.
Semiconductor Manufacturing
Since it is an inert gas which does not interact with any other elements, it is used to create a protective environment when elements are combined to create such as silicon wafers.
Cryogenics
Cryogenics is the study of the production and behavior of materials at very low temperatures. Although liquid nitrogen can be used in some applications, liquid helium is required in applications requiring temperatures lower than 77K.
Airships and Large Display Balloons
Helium is used to inflate airships and large display balloons. The light and non-flammable properties of helium make it a safe and excellent gas for this purpose.
Shielding Gas for Arc Welding
When used in small, controlled quantities as a shielding gas in arc welding, helium dissipates heat and disperses contaminants thereby improving weld characteristics.
Deep Sea Diving
Helium makes a good substitute for nitrogen in the air breathed by deep sea dives as it has less side effects such as it does not cause narcosis like nitrogen.
Helium Mass Spectrometers
The helium mass spectrometer is used to detect and locate small leaks.