some basic information on helium

discovery of helium

Spectroscopic evidence for the presence of helium in the sun was first obtained during a solar eclipse in 1868. A bright yellow emission line was observed and was later shown to correspond to no known element; the new element was named by J. N. Lockyer and E. Frankland from helios [the Greek word for sun]. Helium was isolated (1895) from a sample of the uranium mineral cleveite by Sir William Ramsay.

areas of use

Helium's noncombustibility and buoyancy (second only to hydrogen) make it the most suitable gas for balloons and other lighter-than-air craft. A mixture of helium and oxygen is often supplied as a breathing mixture for deep-sea divers and caisson workers and is used in decompression chambers; because helium is less soluble in human blood than nitrogen, its use reduces the risk of caisson disease, or the bends. Helium can also be used wherever an unreactive atmosphere is needed, e.g., in electric arc welding, in growing crystals of silicon and germanium for semiconductors, and in refining titanium and zirconium metals. It is also used to pressurize the fuel tanks of liquid-fueled rockets. Liquid helium is essential for many low temperature applications.

Within the university the main use of liquid helium is the cooling of "cryostats", a sophisticated measuring instrument based on a superconductive magnet, used within areas of research like solid state physics, atomic physics och biochemistry.

helium is a natural resource and is extracted from natural gas

Helium is rare and costly. Wells in Texas (where the Federal Helium Reserve was established in 1925 near Amarillo), Oklahoma, and Kansas are the principal world source, but minor wells are also found in Algeria, Poland and Russia. Crude helium is separated by liquefying the other gases present in the natural gas; it is then either further purified or stored for later purification and use. Some helium is extracted directly from the atmosphere; the gas is also found in certain uranium minerals and in some mineral waters, but not in economic quantities. It has been estimated that helium makes up only about 0.000001% of the combined weight of the earth's atmosphere and crust; it is most concentrated in the exosphere, which is the outermost region of the atmosphere, 600-1500 mi (960-2400 km) above the earth's surface. Helium is abundant in outer space; it makes up about 23% of the mass of the visible universe. It is the end product of energy-releasing fusion processes in stars (see interstellar matter).

liquid helium from source to customer

The typical path starts in Wyoming, USA where helium gas is extracted from natural gas well and liquefied at a local plant. This is filled into isolated containers and then transported over land to a harbour in New York. After a two weeks journey with a ship the container is loaded on trucks for road transport to a variety of destinations in Europa. Kryolab have two 500 liters LHe-dewars which is regularly transported to Lidingö (near Stockholm) where AGA fills it from one of these containers. At arrival in Lund, the LHe is then transferred into smaller dewars - usually 30 to 100 liters - according to the customers needs.

low-temperature physics

Low-temperature physics, science concerned with the production and maintenance of temperatures much below normal, down to almost absolute zero, and with various phenomena that occur only at such temperatures. The temperature scale used in low-temperature physics is the Kelvin temperature scale, or absolute temperature scale, which is based on the behavior of an idealized gas. Low-temperature physics is also known as cryogenics, from the Greek meaning "producing cold". Low temperatures are achieved by removing energy from a substance. This may be done in various ways. The simplest way to cool a substance is to bring it into contact with another substance that is already at a low temperature. Ordinary ice, dry ice (solid carbon dioxide), and liquid air may be used successively to cool a substance down to about 80 K (about minus 190 C). The heat is removed by conduction, passing from the substance to be cooled to the colder substance in contact with it. If the colder substance is a liquefied gas, considerable heat can be removed as the liquid reverts to its gaseous state, since it will absorb its latent heat of vaporization during the transition. Various liquefied gases can be used in this manner to cool a substance to as low as 4.2 K, the boiling point of liquid helium. If the vapor over the liquid helium is continually pumped away, even lower temperatures, down to less than 1 K, can be achieved because more helium must evaporate to maintain the proper vapor pressure of the liquid helium. Most processes used to reduce the temperature below this level involve the heat energy that is associated with magnetization. Successive magnetization and demagnetization under the proper combination of conditions can lower the temperature to only about a millionth of a degree above absolute zero. Reaching such low temperatures becomes increasingly difficult, as each temperature drop requires finding some kind of energy within the substance and then devising a means of removing this energy. Moreover, according to the third law of thermodynamics, it is theoretically impossible to reduce a substance to absolute zero by any finite number of processes. Superconductivity and superfluidity have traditionally been thought of as phenomena that occur only at temperatures near absolute zero, but by the late 1980s several materials that exhibit superconductivity at temperatures exceeding 100 K had been found. Superconductivity is the vanishing of all electrical resistance in certain substances when they reach a transition temperature that varies from one substance to another; this effect can be used to produce powerful superconducting magnets. Superfluidity occurs in liquid helium and leads to the tendency of liquid helium to flow over the sides of any container it is placed in without being stopped by friction or gravity.

liquefaction

Liquefaction, change of a substance from the solid or the gaseous state to the liquid state. Since the different states of matter correspond to different amounts of energy of the molecules making up the substance, energy in the form of heat must either be supplied to a substance or be removed from the substance in order to change its state. Thus, changing a solid to a liquid or a liquid to a gas requires the addition of heat, while changing a gas to a liquid or a liquid to a solid requires the removal of heat. In the liquefaction of gases, extreme cooling is not necessary, for if a gas is held in a confined space and is subjected to high pressure, heat is given off as it undergoes compression and it turns eventually to a liquid. Some cooling is, however, necessary; it was discovered by Thomas Andrews in 1869 that each gas has a definite temperature, called its critical temperature, above which it cannot be liquefied, no matter what pressure is exerted upon it. A gas must, therefore, be cooled below its critical temperature before it can be liquefied. When a gas is compressed its molecules are forced closer together and, their vibratory motion being reduced, heat is given off. As compression proceeds, the speed of the molecules and the distances between them continue to decrease, until eventually the substance undergoes change of state and becomes liquid. Although before the 19th cent. a number of scientists had experimented in liquefying gases, Davy and Faraday are usually credited with being the first to achieve success. The production of liquefied gases in large quantities (and consequently their use in refrigeration) was made possible by the work of Z. F. Wroblewski and K. S. Olszewski, two Polish scientists. The work of Sir James Dewar is also important, especially in the liquefaction of air and its change to a solid. Heike Kamerlingh Onnes first liquefied helium. The critical temperature of helium is minus 267.9 C, only a few degrees above absolute zero (minus 273.15 C). The processes for the liquefaction of gases as developed by Linde and others form the basis for those used in modern refrigeration.

Kelvin temperature scale

Kelvin temperature scale, a temperature scale having an absolute zero below which temperatures do not exist. Absolute zero, or 0íK, is the temperature at which molecular energy is a minimum, and it corresponds to a temperature of minus 273.15 C on the Celsius temperature scale. The Kelvin degree is the same size as the Celsius degree; hence the two reference temperatures, the freezing point of water (0 C), and the boiling point of water (100 C), correspond to 273.15 K and 373.15 K, respectively. When writing temperatures in the Kelvin scale, it is the convention to omit the degree symbol and merely use the letter K. The temperature scale is named after the British mathematician and physicist William Thomson Kelvin, who proposed it in 1848.

Bose-Einstein condensate

Bose-Einstein condensate, a gas of atoms that has been so chilled that their motion is virtually halted and as a consequence they lose their separate identities and merge into a single entity. The condensate was predicted by Albert Einstein in 1924 based on the system of quantum statistics formulated by the Indian mathematician Satyendra Nath Bose. Quantum theory asserts that atoms and other elementary particles can be thought of as waves. Einstein proposed that as atoms approach absolute zero (minus 273.15 C), the waves expand in inverse proportion to their momentum until they fall into the same quantum state and finally overlap, essentially behaving like a single atom. The phenomenon could not be observed, however, until techniques were developed to reduce temperatures to within 20 billionths of a degree above absolute zero. In 1995 Eric A. Cornell and Carl E. Wieman led a team that isolated a rubidium Bose-Einstein condensate under laboratory conditions. It is believed that this state of matter could never have existed naturally anywhere in the universe, since the low temperatures required for its existence cannot be found, even in outer space. The condensate may be useful in the study of superconductivity (the ability of some materials to conduct electrical current without any resistance) and superfluidity (the ability of some materials to flow without resistance) and in refining measurements of time and distance.

(thanks to http://www.encyclopedia.com)