Writing and erasing nanowires
Researchers report forgoing salaries and taking on fewer graduate students to cope with volatile prices for liquid helium.
Before purchasing an instrument with a recirculating helium system, which only occasionally needs to be topped off with helium, Hayes used a continuous-flow cryostat for chilling samples for NMR analysis, and it consumed an average of 40 liters a day during experiments. Even at the $5 per liter prevailing price in 2010, the liquid helium bill was about $30 000 a year. At current prices, the continuous-flow method would be “simply not sustainable,” Hayes says.
Prices for liquid helium have soared in recent years, and some scientists are reporting difficulty in obtaining the essential commodity for low-temperature research.
Hayes isn’t alone. A recent report prepared by the American Physical Society, American Chemical Society, and Materials Research Society says about 400 US researchers experiment at liquid-helium temperatures, and several thousand scientists use NMR spectrometers, superconducting quantum interference devices, and other instruments requiring liquid helium. Most of the low-temperature experiments and instruments housing superconducting magnets must be continuously replenished with helium, which boils off at a rate of a few liters per day. A typical low-temperature researcher has gone from spending 10% of a typical NSF grant on helium five years ago to more than 25% today, according to the report.
Prices are also volatile. “If I’m doing low-temperature research and purchasing liquid helium and I’m trying to forecast whether I can hire that next PhD student as part of this grant, I have no clue what the helium price is going to do next month,” says Simon Bare of SLAC, who cochaired the committee that wrote the report.
Scientists fear that the impending 2021 shutdown of the US federal helium reserve, mandated by a 2013 law, will cause further price increases and imperil access to the irreplaceable element. In recent years, the reserve has supplied 15–30% of the world’s demand. Helium is a byproduct of natural gas extraction from fields where the helium concentration is high enough—generally 0.3% or greater—to make its separation economical. Most domestic output is from gas fields in Colorado, Kansas, Oklahoma, Texas, Utah, and Wyoming.
A major problem for academic researchers is their lack of purchasing clout, says the report. When supplies are tight, small users aren’t prioritized for deliveries and might not get helium at all. That can spell disaster for an NMR system, which must be cooled constantly to protect its magnet from damage caused by transitioning to a nonsuperconducting state. About 90% of NMR users don’t have the requisite equipment to safely shut down the magnets and must hire a vendor to do so, at a cost of $5000–$10 000, says Hayes. And cooling the magnet back down to a superconducting state can require as much as 1000 liters of helium.
Big helium consumers include MRI (20%), weather and other balloons (14%), and electronics and semiconductors (11%). Today’s high price is not the first time the helium market has caused havoc. A worldwide shortage in 2006–07 forced some researchers to reallocate grant funds or petition funding agencies for additional monies to cover their helium costs (see Physics Today, April 2013, page 28).
Mark Elsesser of the APS public affairs office says most of the more than 70 researchers surveyed for the report consume fewer than 5000 liters each year, and many use less than 1000 liters. Prices paid by individual researchers ranged from $5 to $28 per liter, with no correlation to location or consumption level. Nearly half of the researchers reported paying between $10 and $14 per liter, but 22 paid $15 or more. In 2010 prices were $7–$10 per liter, according to a National Research Council report, Selling the Nation’s Helium Reserve.
Like others who were interviewed, Bare is at a loss to explain the disparity in pricing. “We couldn’t figure out why the price varies so much among the users. There’s no logic.” It could be that “as soon as this one little thing happens somewhere, everything is so interlinked that there is a chain reaction. A plant goes down for maintenance, there’s some interruption, or some huge new demand,” he says. “The damping factor has been the helium reserve, and it will be closing in a few years.”
But Sam Burton, acting field manager for the Bureau of Land Management’s (BLM’s) Amarillo Field Office, which operates the federal helium reserve, says many factors could account for the wide disparity in prices. A purchase made on short notice or in emergencies might cost four to five times what a long-lead-time buyer would pay, he says.
The purchase price for liquid helium for chemist Sophia Hayes of Washington University in St. Louis rose nearly 250% during the five years ending October 2015. (Adapted from the APS/ACS/MRS report Responding to the U.S. Research Community’s Liquid Helium Crisis.)
Since 2009, the open-market price for crude helium (containing 50–70% He) from the reserve has risen more than 60%. Rising prices caused Qatar to expand its helium output, which in turn led to a supply glut that began in 2015 but is not expected to last. The shutdown of a single processing facility for maintenance could cut off a major portion of the world supply, Burton notes.
Future supplies are uncertain. A huge find estimated at 1.5 billion cubic meters was reported this year in the Rift Valley in Tanzania. But Elsesser notes that prices would have to be considerably higher than today’s for industry to invest in the infrastructure needed in that eastern African nation to extract, refine, liquefy, and ship the helium.
The report warns that scientists are abandoning areas of research that require helium and institutions are shying away from hiring new faculty in cryogenic fields. Alexander Barnes, an assistant professor of chemistry at Washington University in St. Louis, uses copious amounts of liquid helium for his experiments in the nascent field of dynamic nuclear polarization. His solid-state NMR system allows him to obtain images of the structures of drugs within cells—something he says isn’t possible with any other imaging technique; operating at 10 K, versus the 100 K achievable with liquid nitrogen, makes the experiments 10 000 times faster.
But Barnes burns through $2000 worth of helium during each six- to eight-hour experiment. At that rate, his grant from the National Institutes of Health is sufficient to pay for only “a couple months” worth of helium. Because innovative junior faculty have less equipment funding available than more established investigators, he worries that aspiring newcomers to the field may be put off by the helium cost. “At $10–$14, we can at least limp along,” Barnes says. But if the price doubles, “this technology development will stop.”
RECOVERY AND RELIEF
A few large universities operate centralized helium recovery and liquefaction plants. William Halperin runs one such facility at Northwestern University. His own lab recycles 95% of its liquid helium. Other campus users—roughly one-third physicists, one-third chemists, and one-third materials scientists, biologists, electrical engineers, and others—recycle most of their helium, but the university still buys about 10 000 liters a year, for which it pays $6.50 per liter under a five-year contract. Halperin says the low price is due to the contract duration and to having a single, high-volume delivery point. He notes that nearby Argonne National Laboratory has no central recycling plant and pays about $3 more per liter for deliveries to multiple points. Central recycling facilities are far more common in Europe and Asia, where helium prices have historically been higher than in North America, he says.
The societies’ report says that a central facility such as Northwestern’s could be economical for institutions consuming 30 000 or more liters per year. A “bare bones” system capable of producing 25–50 liters per hour will cost $1 million to $4 million and require a full-time operator. Cornell and Princeton Universities, the University of Florida, and a few others have such plants. Many top-tier research universities would probably meet the usage threshold, Elsesser says, and Texas A&M University is planning to build one.
Single investigators, or a few that share instruments, can purchase a liquefier capable of recycling 1 liter per hour for $100 000–$200 000, the societies’ report says. The capital investment can be recouped in three years or less. In one case, Carnegie Mellon University chemist Michael Hendrich has saved $175 000 annually on liquid helium from an upfront investment of $150 000 in a liquefier, the report notes.
Washington University’s Hayes says the upfront cost of liquefiers for her four NMR setups is “almost impossible.” Having multiple low-temperature researchers on campus, the university buys in volume, and investigators must coordinate buys and avoid wastage. Hayes’s cost to fill a 100-liter dewar is about $13 a liter, whereas using a 60-liter container would cost $19 a liter. But buying a larger container won’t produce savings if the helium sits around and boils off, and topping off instruments isn’t always a good idea, she notes.
APS and ACS have partnered with the Defense Logistics Agency (DLA), part of the Department of Defense, to create a liquid helium purchasing program. As a broker, DLA increases the purchasing power of the program’s dozen university members. Since the program began in June, participants have received an average savings of 15% on their helium purchases, Elsesser says, with some reporting a 25% reduction.
Efforts to recruit additional universities to the DLA program continue, Elsesser says, but institutions’ existing contractual arrangements and other factors have kept more from signing on.
The BLM’s Hamak says the DLA “is starting to get universities and researchers to understand that the farther out you can put your order in, the cheaper you will get it.”
Adding a recirculating system to an instrument is an upfront expense that few investigators can afford. Beginning in 2014, NSF’s division of materials research has allocated $2 million a year to help with recirculator purchases by grantees who spend $20 000–$30 000 annually on liquid helium. But that’s only enough to help 4–5 investigators per year, out of 60–70. The societies’ report recommends that a portion of the proceeds from helium sales from the federal reserve be set aside to help universities finance new helium recovery facilities and equipment requiring minimal helium recharges.
More buyers of new equipment are demanding “dry” or “cryogen-free” closed systems that require little or no liquid helium replenishment, says Zuyu Zhao, executive vice president of Janis Research. But he notes that due to their mechanical refrigeration systems, those instruments can produce vibrations that make them unsuitable for some experiments.
The societies’ report recommends that BLM eliminate a “major helium requirement” of 7500 liters per year that they say prevents small scientific users from getting a discount on crude helium from the reserve. But that’s a misunderstanding, says Hamak: There is no minimum volume required to obtain the 20% discount; researchers simply have to find a helium supplier that will sell them refined reserve helium. That supplier is then required to purchase a comparable amount of crude helium from the reserve. In practice, however, a small buyer of liquid helium won’t save much after the cost of purifying and liquefying the crude gas is considered. “If your helium requirement is two 500-liter dewars per year, you probably won’t get much of a break,” notes Hamak.
The report also calls for BLM to establish a royalty in-kind program that will provide a source of helium to federal users, including grantees, from BLM-leased natural gas formations, once the reserve is closed. The BLM officials say they will begin that process this spring.