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banded together to form a coherent whole - the superfluid. In an ideal Bose-Einstein Condensate (BEC) at T = 0oK, all particles are in the lowest energy level. In practice, some particles would occupy exited states as shown in Figure 13-05c with the ratio of N(E=0)/N(E![]() |
Figure 13-05c Helium II State [view large image] |
Figure 13-05d1 Helium-4 |
of the entity. The whole thing can move about in near frictionless condition. The small friction is attributed to the excited helium II atoms. |
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usage is on LHC, which uses pressurized helium II as coolant for the parts and saturated helium II as heat transport depositing the heat at the heat exchanger (Figure 13-05g). Pressurized helium II has the additional advantages of minimizing leak and electrical breakdown. |
Figure 13-05f Heat Transport by Superfluid [view large image] |
Figure 13-05g LHC Cooling Scheme [view large image] |
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of Bose-Einstein condensate (BEC). Specifically, ultra-cold sodium atoms are used (each pair of 1/2 spin fermion nuclei form a spin 1 boson at very cold temperature ~ 2![]() ![]() |
Figure 13-05h Slow Light [view large image] |
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When the core of the star collapses to a density of about 1014 gm/cm3 (of the order of that in the nuclei) it causes the atomic electrons to combine with the nuclear protons in the electron capture reaction as shown in Figure 13-05i. This is the point where gravitational forces have won out over the pressure supplied by nuclear matter. |
Figure 13-05i Electron Capture |
Figure 13-05j Neutron Star, Structure [view large image] |
Figure 13-05j shows the structure of a neutron star in several layers over a depth of ~ 10 km: |
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which carry away a lot of energy. The charged protons there also make the core superconducting. The onset of superfluidity in materials on Earth occurs at extremely low temperatures near absolute zero, while it happens in neutron star at temperature near a billion degrees. The difference can be explained by the fact that the low temperature variety involves the very weak force between Cooper pair, while the interaction is via the strong nuclear force between nucleons in neutron star. This information may show us how to achieve superfluidity and superconductor at room temperature on Earth. The X-ray image in Figure 13-05k is colored in red, green and blue, optical data is in gold color. |
Figure 13-05k Superfluid in CasA [view large image] |
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In the Higgs phase, the spin 1 Higgs bosons bound together to form something like the superfluid in the lowest energy state. Although we are not aware the existence of such directly, it is this condensate that endows mass to the elementary particles and ultimately our weight. The mass is generated via the interaction with this Higgs condensate as shown in Figure 13-05l. The top quark (red circle, the size is proportional to the interaction strength) is heavy because its coupling is large - the dragging manifests the effect as mass. The electron (blue circle) is much lighter, while the photon, which has zero mass, can move freely through the condensate. It seems that the Higgs condensate is only a mathematical odd-ball, since it is portrayed to be everywhere even at room temperature but we don't feel a thing about it. Its existence has been finally proven to be real on July 4, 2012 at LHC after spending US$ 4.5 billion just for building the machine alone. The Higgs boson with a mass of 125 Gev was detected by |
Figure 13-05l Higgs Condensate [view large image] |
bombarding the Higgs condensate with high energy protons, some of which excited the Higgs bosons to a detectable level for a fleeting moment. |
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cooling occurs only if the initial pressure and temperature lie inside a curve called the inversion curve (see upper left diagram in Figure 13-05m for hydrogen gas). Ordinary tap water is sufficient for nitrogen gas, but liquid nitrogen (< 70K) must be used to cool hydrogen gas, and liquid hydrogen (< 20K) to cool helium gas. As shown in the upper right diagram of Figure 13-05m for a typical liquefying apparatus, the gas is pre-cooled to a temperature within the inversion curve, and run through the heat exchanger repeatedly until the gas is liquefied. The drawing in lower Figure 13-05m is the schematic diagram of a liquefying plant for mass-produce liquid helium. |
Figure 13-05m Cooling |
Figure 13-05n Laser Cooling [view large image] |