We often see children on the streets with balloons in their hands, a simple toy that is a hit with children no matter what the age. The reason why balloons float in the air is because they are filled with gases that are less dense than air, such as hydrogen and helium. 10 years ago, helium balloons were all over the streets, helium is colorless, tasteless and does not burn, so it is safe and harmless to fill them. But now the balloons are no longer so safe, where the filled gas has become hydrogen, which can burn in case of fire, and there is even a risk of explosion if a large number of balloons rupture centrally. Why should the gas filled in the balloon be replaced with hydrogen?
The only helium gas
The reason for the change is simple: compared to 10 years ago, the cost of helium has more than tripled, and balloons are cheap little toys that naturally cannot afford to be filled with "high-grade" helium gas. So, why has helium become so expensive?
Helium is a true "import", having been discovered outside of the Earth, when French astronomer Pierre-Jeanzan, observing a total solar eclipse in southern India in August 1868, accidentally discovered an unfamiliar bright yellow line in the solar spectrum. At about the same time, the British astronomer Joseph Lockyer also independently discovered this yellow line and named the yellow-emitting element "helium". For more than 20 years afterwards, helium was not found on Earth, and it was like a jewel hanging in the sky, out of reach.
In 1895, the British chemist William Ramsay isolated a colorless and odorless gas from a uranium-containing mineral, and after spectroscopic analysis, he was surprised to find that it was the same "helium" previously found in sunlight. Of course, at this time, people did not know what helium could do, they only knew that it was a gas lighter than air, so they could use it to fill airships and balloons, and the helium they had worked so hard to find in the ground was released into the sky.
As a smaller molecular weight element than hydrogen, helium was one of the first substances produced after the Big Bang, and it is second only to hydrogen in abundance, accounting for about a quarter of the total amount of matter in the universe. However, helium is a very dense and chemically stable element that does not react with almost any substance, so the helium that is native to the universe and emitted by sunlight cannot be retained on Earth.
The only source of helium on Earth is the radioactive material mines. In the molten state at the beginning of the Earth's existence, some radioactive elements were sealed in the mantle and the core of the Earth, and these radioactive elements continuously release alpha particles during the decay process. These alpha particles are essentially helium-4 nuclei composed of two protons and two neutrons, which is what we need for helium. This helium accumulates underground and is collected by people in the process of large-scale mining of radioactive minerals.
Nowadays, the richest helium reserves on earth are found only in a few mining areas in the United States and Qatar. We can neither find more production areas for helium nor a way to make it, and gradually helium is becoming less and less available, and its price is increasing year by year.
Helium is essential for modern society
The price of helium has risen not only because of dwindling reserves, but also because of the discovery that helium has more irreplaceable functions than just an inflatable ball.
Superconducting magnets are a class of metal coils in which the motion of atomic nuclei stops at low temperatures and their resistance almost disappears. Superconducting magnets transmit electrical energy efficiently and produce little heat, and are essential parts of high-tech equipment such as magnetic levitation trains, nuclear magnetic resonance imagers, and high-energy particle colliders. However, metals that can be made into superconducting magnets must be used in ultra-low temperature environments to achieve superconductivity, such as niobium-titanium alloys, which are often made into superconductors and require an ambient temperature of -268.8°C. Only liquid helium can achieve such a low temperature. For example, the 27 km long European Hadron Collider uses about 130 tons of liquid helium to cool its superconducting magnets to -271.3°C. This 130 tons of liquid helium accounts for 1% of the global helium production, not to mention the liquid helium used in maglev trains and MRI machines in hospitals around the world.
Helium is also often used as a protective gas in atomic reactors, gas pedals, lasers and other equipment to isolate oxygen to protect metals from oxidation, and is commonly used in industry to isolate oxygen when smelting and welding metals. Because helium is so diffusible and very small amounts can be easily detected, it can also be used in sealed machinery and equipment, such as spacecraft and rockets, to test their hermeticity.
Helium also has a very interesting use. Many people have had the experience of taking a breath of helium and their voice becomes sharp and thin. In fact, people who have been deep diving for a long time speak like this when they have just come ashore, precisely because they have inhaled a certain amount of helium. When people are deep diving, the pressure on the human body increases, the amount of air dissolved into the blood becomes more, and the amount of nitrogen, the main component of air, is more in the body. When the partial pressure of nitrogen in the blood reaches a certain level, people become anesthetized and even faint, commonly known as "nitrogen intoxication", which is very dangerous during diving. Helium has a very low solubility in the blood and does not remain in the body in large quantities even under high pressure. Therefore, by adding helium to oxygen tanks instead of nitrogen, people can avoid nitrogen intoxication during long deep dives.
The most common contact with helium is in supermarkets, where the bar code scanners used at the cashier's office use He-Ne lasers for identification. The helium-neon laser is filled with helium and neon gas in a volume ratio of about 10:1. When exposed to light, the helium gas transmits converging light energy and the neon gas is excited to produce radiation, emitting a laser. As the first gas lasers, helium-neon lasers are cheap and consume little energy, so they are widely used in various bar code scanners. In addition to bar code scanners, He-Ne lasers are also used in devices such as microscopes, spectrometers, and optical disk drives.
Open source and conserve helium
On the one hand, there are dwindling helium stocks and on the other hand, helium usage is gradually expanding. With demand outstripping supply, a price increase for helium is inevitable. Even so, at current levels of use, there are only about 20 years of helium left on the planet. Faced with this situation, researchers have opened their brains.
The most straightforward solution is to cut costs, and nowadays the MRI machines commonly used in hospitals are basically equipped with liquid helium devices with good containment and reduced evaporation, which greatly reduces the demand for liquid helium. 2014, scientists in China developed the first industrial helium recycling system, which can recover the helium used in industrial production containing impurities and purify it for reuse. The system is now capable of purifying helium with a purity of only 10% to a purity of more than 99.5%.
Since superconducting magnets are the largest users of helium, is there any way to reduce the amount of helium used in this field? More scientists have tried to replace liquid helium refrigeration with other refrigeration methods, using liquid helium-free chillers to reach the operating temperature of superconducting magnets. Recently, an MRI imager using liquid helium-free superconducting magnets, jointly developed by several research institutions including the University of Nottingham in Ningbo, Zhejiang Province and Zhejiang University School of Medicine, has been put into operation. The superconducting magnet of this imager replaces the original refrigerant liquid helium with a low-cost and safe copper strip, which is cooled by direct conduction cooling technology.
Of course, open source is the fundamental way to ensure an endless supply of helium. The Earth's atmosphere contains about 0.0005% helium, albeit very little, and when helium is in short supply, people use the principle that gases have different boiling points to separate it from the atmosphere. It was in the midst of such bitterness that a surprising amount of helium was found in the Moon. It turns out that the helium particles radiated from the Sun can "settle" in the lunar soil because the Moon itself has no magnetic field. In contrast, the helium particles radiated to the Earth slowly spread along the Earth's magnetic field and eventually leak through the atmosphere into outer space. Scientists have calculated that by heating the lunar soil to 80°C, 1 ton of helium can be extracted from about 200 million tons of lunar soil, while the equivalent amount of Earth soil can produce only 10 kg of helium. As we speed up the process of developing the moon, perhaps in the future the moon can become a Persian Gulf-like energy base and we can get rid of the crisis of helium deficiency.
In the days when we were happily playing with helium balloons, I don't think anyone could have imagined that in just a decade or so we would be faced with the prospect of running out of helium, right? How many other resource crises are coming besides helium? Conserving resources is not just a slogan, it is the best way to ensure our future well-being.
