Why Helium Is More Valuable Than Most People Think 为什么氦比大多数人想象的更有价值：从派对气球到MRI扫描仪
If you ask most people what helium is for, they will say balloons. That is a bit like saying steel is for paperclips. Helium is, in truth, one of the most strategically important materials in modern civilization — and unlike almost everything else we mine or extract, it is genuinely irreplaceable for many of its uses. When a helium atom is released into the atmosphere, it rises, diffuses, and eventually escapes Earth's gravity entirely. There is no recycling loop. No substitute. Every helium atom we release today is an atom our grandchildren will never have.
Helium occupies position 2 on the periodic table, right after hydrogen. It is the lightest of the noble gases — a family of elements whose defining trait is a profound reluctance to form chemical bonds. A helium atom has two protons, two neutrons (in its most common isotope), and two electrons filling its only electron shell. That closed shell makes helium chemically inert. It will not react with anything, under any ordinary conditions, ever. This inertness, combined with its extraordinarily low boiling point — just 4.2 Kelvin, or -268.93°C — gives helium its unique and irreplaceable role in technology.
A Cosmic Element Trapped Underground
Helium is cosmically abundant — it makes up about 24% of the observable universe's ordinary matter, second only to hydrogen. The Sun fuses roughly 600 million tonnes of hydrogen into helium every second. And yet, here on Earth, helium is vanishingly rare. The atmosphere contains only about 5.2 parts per million of helium — roughly 0.0005% by volume. At that concentration, extracting helium from air would be comically expensive.
The helium we use comes from a different source entirely: the slow, patient decay of radioactive elements deep underground. When uranium-238 or thorium-232 undergoes alpha decay, the alpha particle it emits is, in fact, a helium-4 nucleus. Over geological timescales — hundreds of millions of years — this radiogenic helium accumulates in the same natural gas reservoirs that trap methane. Some gas fields contain negligible helium; others, particularly in the American Southwest, Qatar, Algeria, and Russia, can contain up to 7% helium by volume.
This is why helium is almost always produced as a co-product of natural gas extraction. Methane is separated and sent to market; the helium-rich stream goes through cryogenic distillation to concentrate the helium to 99.995% purity or better. The entire global helium supply depends on a handful of gas fields where the geology happened to be right. When those fields deplete, or when geopolitical pressures disrupt access to them, the world faces a helium shortage.
The Liquid That Makes MRI Possible
The largest single use of helium — accounting for roughly 30% of global consumption — is in magnetic resonance imaging. An MRI scanner contains a superconducting magnet, typically made of niobium-titanium or niobium-tin alloy. When cooled below its critical temperature, this alloy can carry enormous electric currents with zero resistance, generating the intense, exquisitely stable magnetic fields (typically 1.5 to 3 Tesla, and up to 7 Tesla for research systems) that make MRI imaging possible.
The critical temperature of niobium-titanium is about 9.2 K. The only practical way to maintain this temperature in a hospital setting is to immerse the magnet coils in a bath of liquid helium. A typical MRI scanner contains 1,500 to 2,000 liters of liquid helium. The helium does not wear out — it circulates in a closed system, with boil-off gas captured and re-liquefied in modern machines. But older systems lose about 1-2% of their helium per month to boil-off, requiring periodic refills.
When an MRI magnet "quenches" — a rare but serious event where the superconducting state is suddenly lost — the entire liquid helium inventory can boil off in seconds, filling the room with a dense cloud of helium gas. This is dangerous (helium displaces oxygen) and expensive — a full quench on a large MRI can cost $100,000 or more in helium alone. Hospitals go to considerable lengths to prevent this, including maintaining backup chillers and rigorous monitoring systems.
Semiconductors and the Helium-3 Enigma
Helium's second act is in semiconductor manufacturing, where it plays multiple roles. In plasma etching — the process that carves transistor patterns into silicon wafers — helium is used as a carrier gas that dilutes reactive plasma species and controls etch rates with remarkable precision. Its high thermal conductivity (the highest of any gas except hydrogen, which is too reactive to use) makes it an excellent coolant, drawing heat away from wafers during processing.
But the most exotic use in microelectronics involves not ordinary helium-4, but its far rarer isotope, helium-3. Helium-3 makes up only about 0.000137% of natural helium — roughly one atom in 730,000. It has two protons but only one neutron, giving it unusual quantum properties. Helium-3 is essential for neutron detectors used in border security and nuclear non-proliferation. It is also used in dilution refrigerators, which can reach temperatures below 0.002 K — essential for quantum computing research. A single litre of helium-3 gas can cost over $3,000. The global supply of helium-3 is so limited that demand consistently outstrips production, with much of the available stock coming from the decay of tritium in nuclear weapons stockpiles — an unlikely and dwindling source.
Rockets, Welders, and Deep-Sea Divers
When a rocket launches, its fuel tanks must be pressurized to feed propellants into the engines at enormous flow rates. Helium does this job because it is light, inert, and will not react with cryogenic liquid oxygen or liquid hydrogen. Every SpaceX Falcon 9, every NASA SLS, every Ariane rocket uses helium to pressurize its tanks. A single Space Shuttle launch consumed about 1.4 million standard cubic feet of helium — the equivalent of roughly 40,000 party balloons.
In welding, helium serves as a shielding gas that prevents molten metal from reacting with atmospheric oxygen. Mixed with argon, it produces a hotter arc and deeper weld penetration, especially useful for aluminum and stainless steel. And in deep-sea diving, helium replaces nitrogen in breathing gas mixtures. Nitrogen, under the high pressures of deep diving, dissolves into body tissues and can cause nitrogen narcosis — a drunken-like impairment that can be fatal at depth. Helium dissolves far less readily and is not narcotic. The squeaky voice that divers get from helium-oxygen mixtures (heliox) is a small price to pay for not drowning in confusion at 100 meters.
The Helium Crisis That Nobody Talks About
The world has been through multiple helium shortages. The US Federal Helium Reserve — a vast underground storage facility in the Texas Panhandle, created in 1925 to secure helium for military airships — once held over 30 billion cubic feet of helium and supplied roughly 30% of the global market. But a 1996 law required the Bureau of Land Management to sell off the reserve to pay down debt, and by 2021, the reserve had effectively stopped commercial sales. The sudden withdrawal of this supply shocked the market.
Meanwhile, the rise of new helium sources has been slow. Qatar has become a major supplier through its liquefied natural gas operations, but geopolitical tensions in the Middle East add uncertainty to supply chains. Russia's Amur gas processing plant, poised to be a major new source, was delayed by a fire in 2022 and sanctions following the invasion of Ukraine. New helium production facilities in Canada and Tanzania are in development but years from reaching full capacity.
The result is a structurally tight market where prices have risen sharply. Helium that cost $2-3 per thousand cubic feet a decade ago can now cost $20 or more, and spot prices during shortages have reached $100. Laboratories and universities have been forced to cancel experiments or shut down instruments because they simply could not obtain helium. The American Physical Society, American Chemical Society, and other scientific organizations have repeatedly called for better helium conservation policies, arguing that the US government should stop selling helium at below-market prices and enforce stricter recovery requirements for major users.
Smarter Ways Forward
The good news is that helium can be used much more efficiently than it typically is. Modern MRI scanners equipped with helium recovery and re-liquefaction systems lose almost no helium during normal operation. Semiconductor fabs are increasingly installing helium recycling systems that capture spent gas, purify it, and feed it back into the process. The Large Hadron Collider at CERN, one of the world's largest helium consumers (about 130 tonnes of liquid helium cool its 27-kilometer ring of superconducting magnets), operates a closed-loop recovery system that captures boil-off and re-liquefies it.
On the exploration side, there is growing interest in searching for helium specifically, rather than relying on it as a byproduct of natural gas. Wildcat helium exploration is happening in Saskatchewan (Canada), the Tanzanian Rift Valley, and several US states. Some explorers are targeting nitrogen-rich gas fields where helium is often concentrated, as the nitrogen — like helium — originates from basement rock rather than organic decay. These "green helium" exploration efforts treat helium as a primary product, not a co-product, and could significantly diversify supply.
And then there is the futuristic possibility: lunar helium-3. The Moon's surface, unprotected by an atmosphere or magnetic field, has been bombarded by the solar wind for billions of years, implanting helium-3 into the lunar regolith. Estimates suggest the Moon may contain over a million tonnes of helium-3 — enough, if fusion reactors that use helium-3 are ever developed, to power human civilization for centuries. For now, lunar helium-3 mining remains firmly in the realm of science fiction, but it serves as a reminder: the things that are most valuable are often the things we cannot see, cannot touch, and cannot make more of.
Frequently Asked Questions
Why does breathing helium make your voice squeaky?
The speed of sound in helium is about three times faster than in air (972 m/s versus 343 m/s at room temperature). When you inhale helium, your vocal cords vibrate at the same frequency as normal, but the sound travels through helium much faster. Your vocal tract resonates at higher frequencies, shifting the timbre of your voice to a higher pitch. This effect is temporary and harmless in small amounts, but breathing pure helium can cause asphyxiation by displacing oxygen — never inhale helium directly from a pressurized tank.
Why is helium so much more expensive than it used to be?
Several factors have driven helium prices upward: the US Federal Helium Reserve's exit from commercial sales, geopolitical disruptions to major suppliers (Qatar, Russia), rising demand from the semiconductor and medical sectors, and the long lead times required to bring new production online. Unlike most commodities, helium cannot be stockpiled easily — it must be stored in specially engineered underground caverns or in cryogenic tanks. The market is opaque, with long-term contracts dominating, and spot shortages can drive extreme price spikes.
Is there a replacement for liquid helium in MRI machines?
Partially. Several manufacturers have developed "low-helium" or "zero-boil-off" MRI scanners that use sealed helium systems requiring only 7-10 litres instead of 1,500-2,000 litres. These systems capture and re-liquefy helium that would otherwise boil off, dramatically reducing consumption. However, these systems still require some helium, and the superconducting magnets still depend on the unique cooling power of liquid helium. A true helium-free MRI scanner would require room-temperature superconductors, which remain one of the holy grails of condensed matter physics.
References
如果问大多数人氦气是干什么用的，他们会说气球。这就好比说钢铁是用来做回形针的。事实上，氦是现代文明中最具战略重要性的材料之一——而且与几乎所有我们开采或提取的物质不同，它在许多用途上真正不可替代。当一个氦原子被释放到大气中时，它会上升、扩散，最终完全摆脱地球引力。没有回收循环，没有替代品。我们今天释放的每一个氦原子，都是我们的子孙后代永远无法再拥有的原子。
氦在周期表中占据第2位，紧随氢之后。它是最轻的稀有气体——来自一个以难以形成化学键为特征的家族。一个氦原子有两个质子、两个中子（在其最常见的同位素中）和两个电子，恰好填满其唯一的电子层。这个封闭的电子层使氦在化学上完全惰性。在任何普通条件下，它永远不会与任何东西反应。这种惰性，加上其极低的沸点——仅4.2开尔文，即-268.93°C——赋予了氦在技术中独特且不可替代的角色。
被困在地下的宇宙元素
氦在宇宙中极为丰富——它约占可观测宇宙普通物质的24%，仅次于氢。太阳每秒将约6亿吨氢聚变为氦。然而在地球上，氦却少得惊人。大气中仅含有约百万分之5.2的氦——大约0.0005%体积。在这种浓度下，从空气中提取氦的成本会高得离谱。
我们使用的氦来自完全不同的源头：地下深处放射性元素的缓慢、耐心的衰变。当铀-238或钍-232发生α衰变时，所发射的α粒子实际上就是一个氦-4核。在地质时间尺度上——数亿年——这种放射成因氦积累在困住甲烷的同一天然气储层中。某些气田几乎不含氦；其他的，尤其是在美国西南部、卡塔尔、阿尔及利亚和俄罗斯，氦含量按体积可达7%。
这就是为什么氦几乎总是作为天然气开采的副产品生产。甲烷被分离并送往市场；富氦流通过低温蒸馏将氦浓缩至99.995%或更高的纯度。整个全球氦供应依赖于少数几个地质条件恰好适宜的气田。当这些气田枯竭，或当地缘政治压力破坏对其的访问时，世界就面临氦短缺。
使MRI成为可能的液体
氦最大的单一用途——约占全球消费量的30%——是磁共振成像。一台MRI扫描仪包含一个超导磁体，通常由铌钛或铌锡合金制成。当冷却到临界温度以下时，这种合金能以零电阻承载巨大电流，产生强烈的、极其稳定的磁场（通常1.5至3特斯拉，研究系统高达7特斯拉），使MRI成像成为可能。
铌钛的临界温度约为9.2 K。在医院环境中维持这一温度的唯一实用方法是将磁体线圈浸入液氦浴中。一台典型的MRI扫描仪含有1500至2000升液氦。氦不会耗尽——它在封闭系统中循环，现代机器中蒸发的气体会被捕获并重新液化。但旧系统每月因蒸发损失约1-2%的氦，需要定期补充。
当MRI磁体"失超"——一种罕见但严重的事件，其中超导状态突然丧失——整个液氦库存可能在几秒钟内蒸发，使房间充满浓密的氦气云。这很危险（氦取代氧气）且昂贵——大型MRI的一次完全失超仅氦的成本就可能达到10万美元或更高。医院不惜代价防止这种情况，包括维护备用冷却装置和严格的监控系统。
半导体与氦-3之谜
氦的第二大用途是半导体制造，在其中扮演多重角色。在等离子体蚀刻——在硅晶圆上雕刻晶体管图案的工艺——氦用作载气，稀释反应性等离子体物种并以惊人的精度控制蚀刻速率。其高导热性（除氢气外所有气体中最高的，而氢气过于活泼无法使用）使其成为优秀的冷却剂，在加工过程中将热量从晶圆带走。
但微电子中最奇特的用途涉及的不是普通氦-4，而是其远为稀有的同位素氦-3。氦-3仅占天然氦的约0.000137%——大约每73万个原子中只有一个。它有两个质子但只有一个中子，赋予它不同寻常的量子特性。氦-3对于边境安全和核不扩散中使用的中子探测器至关重要。它也用于稀释制冷机，可以达到0.002 K以下的温度——对量子计算研究至关重要。一升氦-3气体的价格可超过3000美元。全球氦-3供应如此有限，需求持续超过产量，大部分可用库存来自核武器储备中氚的衰变——一个不太可能且日渐枯竭的来源。
火箭、焊工和深海潜水员
火箭发射时，其燃料箱必须加压，以巨大流速向发动机输送推进剂。氦完成这项工作，因为它轻、惰性、且不会与低温液氧或液氢反应。每一枚SpaceX猎鹰9号、每一枚NASA SLS、每一枚阿丽亚娜火箭都使用氦为其燃料箱加压。一次航天飞机发射消耗约140万标准立方英尺的氦——大约相当于4万个派对气球。
在焊接中，氦用作保护气体，防止熔融金属与大气中的氧反应。与氩混合时，产生更热的电弧和更深的焊缝渗透，特别适用于铝和不锈钢。而在深海潜水中，氦替代呼吸气混合物中的氮。在深海高压下，氮溶解在身体组织中，可导致氮麻醉——一种类似醉酒的损伤，在深处可能致命。氦溶解得远比氮少，且不具麻醉性。潜水员使用氦氧混合气（heliox）发出的尖锐嗓音，与在100米深处不至于在困惑中溺水相比，是微不足道的代价。
无人谈论的氦危机
世界经历过多次氦短缺。美国联邦氦储备——德克萨斯州潘汉德尔一个巨大的地下储存设施，创建于1925年，旨在为军用飞艇保障氦供应——曾持有超过300亿立方英尺的氦，供应约30%的全球市场。但1996年的一项法律要求土地管理局出售储备以偿还债务，到2021年，该储备已实际上停止了商业销售。这一供应的突然退出震动了市场。
与此同时，新氦源的崛起一直缓慢。卡塔尔通过其液化天然气业务已成为主要供应国，但中东的地缘政治紧张局势为供应链增添了不确定性。俄罗斯的阿穆尔天然气加工厂即将成为重要的新来源，却因2022年的火灾和入侵乌克兰后的制裁而延迟。加拿大和坦桑尼亚的新氦生产设施正在开发中，但距离达到满负荷生产还有数年时间。
结果是一个结构性紧张的市场，价格急剧上涨。十年前每千立方英尺2-3美元的氦现在可能达到20美元以上，短缺期间的现货价格已达100美元。实验室和大学因为根本无法获得氦而被迫取消实验或关停仪器。美国物理学会、美国化学学会和其他科学组织一再呼吁更好的氦保护政策，认为美国政府应停止以低于市场的价格出售氦，并对主要用户执行更严格的回收要求。
更聪明的解决之道
好消息是，氦的使用效率可以比通常高得多。配备氦回收和再液化系统的现代MRI扫描仪在正常运行时几乎不损失氦。半导体工厂日益安装氦回收系统，捕获废气，净化后回馈到工艺中。欧洲核子研究组织的大型强子对撞机是世界上最大的氦消费设备之一（约130吨液氦冷却其27公里长的超导磁体环），运行着一个闭环回收系统，捕获蒸发气体并将其重新液化。
在勘探方面，人们越来越关注专门寻找氦，而不是依靠作为天然气副产品。独立氦气勘探正在加拿大萨斯喀彻温省、坦桑尼亚裂谷和美国若干州进行。一些勘探者瞄准富氮气田，氦通常在其中富集，因为氮——如氦——来源于基底岩石而非有机物衰变。这些"绿色氦"勘探工作将氦视为主要产品而非副产品，可以显著多样化供应。
然后还有未来主义的可能性：月球氦-3。月球表面没有大气层或磁场的保护，遭受太阳风轰击数十亿年，将氦-3植入月壤。估计月球可能含有超过100万吨的氦-3——如果使用氦-3的聚变反应堆被开发出来——足以支撑人类文明几个世纪。目前，月球氦-3开采仍坚定地停留在科幻领域，但它作为一种提醒存在：最有价值的东西往往是那些我们看不到、摸不着、无法制造更多的存在。
常见问题
为什么吸入氦气会让声音变尖？
声音在氦气中的速度约为空气中的三倍（室温下972米/秒对比343米/秒）。吸入氦气时，你的声带以正常频率振动，但声音穿过氦气的速度快得多。你的声道在更高频率共振，将声音的音色转移到更高的音调。这种效果是暂时的，少量无害，但吸入纯氦会通过取代氧气而导致窒息——切勿直接从加压气瓶吸入氦气。
为什么氦气比过去贵得多？
多种因素推动氦价上涨：美国联邦氦储备退出商业销售，主要供应国（卡塔尔、俄罗斯）的地缘政治干扰，半导体和医疗领域不断增长的需求，以及新产能上线需要漫长的提前准备时间。与大多数商品不同，氦不易储存——必须在专门设计的地下洞穴或低温储罐中储存。市场不透明，长期合同占主导地位，现货短缺可能引发极端价格飙升。
MRI机器中的液氦有替代品吗？
部分有。几家制造商已开发出"低氦"或"零蒸发"MRI扫描仪，使用密封氦系统，仅需7-10升而不是1500-2000升。这些系统捕获并重新液化原本会蒸发的氦，大幅减少了消耗。然而，这些系统仍需要一些氦，超导磁体仍依赖液氦的独特冷却能力。真正的无氦MRI扫描仪需要室温超导体，这仍是凝聚态物理学中的圣杯之一。