|Dr. Lawrence, L. R. Jr. High Temperature Superconductivity: The Product and their Benefits. Oak Ridge National Laboratory. July 1998.||"Considering also the added cost of the helium gas, liquid helium costs about $5.00 per liter (1) whereas liquid nitrogen is only $0.10 per liter."||$5.00/liter|
|Kühlwein, Ludwig. Helium Recovery: Tailor-made and Absolutely Gastight. Bauer Kompressoren GmbH. April 11, 2007.||"In local distribution centres, the helium is decanted into smaller containers for delivery to the end user; 1 l liquid helium costs at present about 7 to 10 Euros."||$9.42–$13.45/liter|
|Smith, Robert Carl. Understanding Magnetic Resonance Imaging. CRC Press. 1998.||"Older designs were made more wasteful of the liquid helium, which boiled off at rates of up to 21/h. These older systems were significantly more expensive to maintain because liquid helium costs about $5.00/ l."||$5.00/liter|
|Versatile set of Alloys Could Enhance Performance of Cyrocooler. Ames Laboratory. August 21, 2000.||"Gschneidner noted that liquid helium costs about $3.50 per liter in the United States and up to $15 a liter in Europe and Japan. "If you're spending between $50,000 and $80,000 a year on liquid helium, you'd repay the cost of the cryocooler pretty fast," he said."||$3.50/liter
(Europe & Japan)
|Dr. McChesney. Cyrogenic Facility. Brookhaven National Lab. July 29, 2005.||"Per BNL Supply Material Division, price of liquid helium is $ 3.25 per Liter in 2001 (in 60, 100, 250 or 500 L size). Delivery to BNL is limited to Monday, Wednesday and Friday only. A $400 shipping charge will be added if order is not placed in time.... Liquid helium is cold (-269 degree Celsius or 4.5 K) and expensive.||$3.25/liter|
In 1868, Pierre Janssen, a French astronomer observed a strange yellow spectral line from a solar eclipse. This line was identified as the element, helium which has the atomic number of 2. Of all of the elements, helium is the second most abundant, the least reactive, and the second lightest in weight. Its molecules are very small which accounts for its high diffusibility. In addition to this, the molecules have a weak force of attraction. Due to this property, helium's boiling point is 4.22 K which is also the lowest boiling point of all gases.
Due to its unique properties, helium is most commonly found in its gaseous state. In July 1908, Kamerlingh Onnes first liquefied Helium-4. In order to liquefy helium, very low temperatures are needed. Helium will remain in its liquid state from 4 K down to absolute zero. It will not become solid unless it is under high pressure.
The helium liquefaction process uses a great amount of energy. At the University of Konstanz, producing 20 liters uses a 90 kW electric motor and is fed by a compressor with a 10 bar pressure output and 800 Nm3/h capacity. The evaporated gas is collected and transported through a pipe network to a gas balloon where it is compressed and stored under pressure until it is ready to be liquefied again.
Most of the energy used in this liquefaction system is used in the process of cooling. Since helium must be cooled down to 4 K, the process makes liquid helium very expensive compared to other elements. In fact, liquid nitrogen which must be cooled to only 77 K can cost as low as $0.15 per liter while liquid helium's price can range from $3.25 to $15.00.
Modern medical and science technologies have taken advantage of liquid helium. An important medical technology is Magnetic Resonance Imaging (MRI), a machine that requires superconductive metals. Superconductivity is the ability to conduct large amounts of electric current with negligible resistance. Liquid helium's low temperature is used to cool materials that become superconductive. Liquid helium is also used in cryogenics and is typically the gas pumped back and forth by a compressor in a cyrocooler. Without liquid helium, important technologies such as MRI and cryogenics will not be possible.
Nadya Dillon -- 2007