[en] The cryogenic department of the IPN realized a cryopump of the liquid helium bath type. Performances are measured (pumping speed, consumption of cryofluids, holding time)

[en] Continuation of present activities and further developments in the application of superconductivity is crucially dependent on the continued availability of helium. Even the changes that are likely to occur due to the use of higher temperature superconductors will probably not affect the need for helium since in order to attain appropriate current carrying capacity in the new materials liquid helium temperatures may well be needed. World wide use of helium in 1988 is estimated to have been 2.3 to 2.4x10⁹ std. cubic feet; up from 2.1x10⁹ scf estimated for 1987. The 1989 use is expected to expand by ∼10%. On September 30, 1987 the date of the last report, 36x10⁹ scf of helium was in the U.S. storage facility. One has to conclude that even with the estimated 10% annual increase in the use of helium ∼10 years of product is in reserve. Using the simplest model where a constant recovery of helium from natural gas accounts for a portion of the yearly use one still finds the U.S. reserve exhausted by the year 2001. The crisis can only be avoided by a less than 10% yearly growth in use or by new extraction plants recovering more helium from natural gas use. A critical review is presented covering the trends in other uses, estimation of reserve depletion and availability of new plants utilizing new sources. This includes an estimate of the onset of the crisis in availability and cost of helium. (author) 3 figs., 1 tab

[en] Calculated values of the acoustic velocity are presented for single-component and two-component, two-phase mixtures. Three different analytic models were employed. For purposes of comparison, all three models were used in making acoustic-velocity calculations for single-component, equivalent bubbly two-phase mixtures (with insoluble gas) of oxygen and helium and hydrogen and helium. In all cases the results are shown graphically so that the effects of variation in quality or void fraction, temperature and pressure are illustrated. 29 references

[en] In this work the deign and construction of a small hydrogen liquefier (two liters per hour maximum production) is described. The isenthalpic expansion process is used, because its construction is simple and it is generally cheaper to operate. A comparison with other liquefier processes, and considerations about their basic theory are also presented. (author)

[en] Neutron diffraction studies of liquid helium led to a simplified model of the temperature dependence of elementary excitations around the lambda-point. (LL)

[en] A cryogenic freezer of the elongated, tunnel-type is disclosed in which a centrally located blower recirculates injected cryogenic refrigerant at extremely high velocities through a pair of minimum size product contact chambers. In one preferred embodiment, the cross-sectional area of the product contact chamber is variable so as to maintain minimum sizes for products of different height

No abstract available

[en] A multiple plane spoke structure is disclosed for supporting a superconducting rotor assembly of a dynamoelectric machine. A plurality of generally radially extending support spokes interconnect an ambient temperature rotor portion with a cryogenic temperature rotor portion. The spokes are secured in tension between the two rotor portions and are displaced one from another along the axial length of the rotor member. The spokes are preferably grouped together in sets of at least two each with at least one of the spokes being angularly displaced with respect to the remaining spokes. The proper placement of these groups of spokes is determined by comparing the maximum deflection of the rotor assembly at the operational frequency to the maximum allowable deflection which can be tolerated under steady state conditions. Each spoke projects through radial openings in the core of the field winding structure. These openings are preferably located in the pole portions of the rotor core structure which lie intermediate of next adjacent field winding groups

[en] The first part of this chapter gives an introduction to heat transfer and cooling techniques at low temperature. We review the fundamental laws of heat transfer (conduction, convection and radiation) and give useful data specific to cryogenic conditions (thermal contact resistance, total emissivity of materials and heat transfer correlation in forced or boiling flow for example) used in the design of cooling systems. In the second part, we review the main cooling techniques at low temperature, with or without cryogen, from the simplest ones (bath cooling) to the ones involving the use of cryocoolers without forgetting the cooling flow techniques

[en] Treating dermatosis with liquid nitrogen as cryogen (substance generating cold) allows cellular destruction in more than 5 mm depth, making it indispensable to use it treating cutaneous cancers; besides that, it is cheap, easy to conserve and manage, and it is not considered flammable or toxic. Its applying retains the growth factor inside the injury, the collagen is not damaged as it is in burning by hot, there is not almost injury contraction, the perineurium is not altered, and when the tissue necrosis takes place, it retains tissue necrosis factor, helping to increase the necrosis of tissues. Taking into account the high incidence of dermatosis that can be treated with cryogen, in our consultation; we decided to generalize this treatment at the Provincial Interior Ministry Clinic. Plantar warts represent a big percent, limiting our patients in developing their working activities. This cutaneous viral disease is favored by the patients' systemic immunodepressions, hyperhidrosis and podalic disturbances. We selected the patients assisting to our extern al consultation with plantar wart clinical diagnosis in the period from September 2006 to September 2007. They signed an act of informed consent where the possible side effects are explained. Liquid nitrogen was applied with cotton applicators once a week after mechanical reduction. We made a clinical evolving evaluation fortnightly during the treatment, according to the elements and clinical characteristics referred by the patient, and proved by the physical examination carried out by the main investigator, because of the likelihood of short and long time side effects. This investigation demonstrated that cryotherapy is efficacious in treating plantar warts, since all the patients were healed in a short time period, most of them without side effects