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The results of a study of the properties of aerogel manufactured at the Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, are presented. The technology of the production of aerogel samples and the optical characteristics of these samples are briefly described. A formula relating the refractive index of the aerogel to its density with regard to the dispersion of light is analyzed. The results of testing of an aerogel threshold Cerenkov counter are presented. Testing was performed using a beam of charged particles with momenta p ranging from p = ∼ 0.4–2.5 GeV/с. The efficiency of pion detection with p ≥ 1 GeV/с was ∼97%; the efficiency of proton detection with p ≤ 2.5 GeV/c, ∼4%.

Today cryogenic circulating systems are used in many branches of technology as cryostats for superconducting devices and in cryogenic vacuum pumps where a high vacuum or a high capacity is required. One of the most important elements in these systems is the flow driver - the device which causes the cryogenic liquid to circulate. Systems which include a mechanical or jet pump are widely used, as are those in which the liquid is circulated by a compressor in a single-loop system. The operational principle of a new device for circulating cryogenic liquid - an expander pump - is as follows. Previously compressed gas, with a temperature somewhat higher than the saturation temperature, expands in a cylinder and does work by pumping the liquid. At the end of the expansion process, part of the working gas condenses and can completely or partially compensate the loss of liquid in the utilization loop. The use of an expander pump has many advantages over other flow drivers. These advantages are discussed.

Results are shown of the trials of an experimental gas-dynamic cryogenerator. In contrast to the classical resonance tube, an annular gas jet is used. It is shown that periodic alternation of the resonance zones resulting from the cellular structure of the jet takes place when the tube moves relative to the nozzle. A schematic is provided of the gas-dynamic cryogenerator. One of the most important characteristics of a gas-dynamic cryogenerator is the temperature level at which the heat is diverted to the terminal heat exchanger. The trials of the experimental gas-dynamic cryogenerator showed that it is more efficient than the expanding throttling devices and is a promising apparatus for application in refrigerating and cryogenic engineering.

Temperature fields were determined theoretically and experimentally for a system of concentric cylinders with gas filling the gap between cylinders under boundary conditions characterized by constant differences in the values of the temperatures at the ends of the connection and by the existence of heat transfer obeying the Fourier law on the cylindrical surfaces of the connection elements.

The fundamental parameters of the unsteady processes of filling a vapor cavity in a short pipeline with water and cryogenic fluids are compared. The influence of flow interaction with the channel walls on the regularities of acceleration and deceleration is established.

In connection with the wide use of cryogenic products -liquid nitrogen, oxygen~ methane, hydrogen, helium, and the like -in the national economy, the problem of cooling cryoproducts with reference to their boiling points at atmospheric pressure (for example, cooling helium to 1.8~ and lower for cryostat superconducting electrical devices; cooling nitrogen, oxygen, and other products from air-separating units with the objective of eliminating losses of them from evaporation during extended transporting and storage) is an urgent one [1-4].

At the present time there are well-developed methods for the calculation of the not fully established motion of a liquid in pipelines completely filled with liquid. Calculation of the hydrodynamic parameters of the not fully established motion of a liquid during the filling of a pipeline is complicated from a mathematical point of view, since in this case it is required to solve equations of motion of a liquid, the boundary condition to which is given at a moving boundary. In [i] a method is proposed for calculating the process of the filling of a pipeline of both constant and variable cross section, under the assumption that the liquid is incompressible. However, in the cases of the greatest practical importance, characterized by considerable fluctuations of the pressure of the liquid, the assumption of its incompressibility leads to significant errors in the calculation [2], It is particularly important to take into account the compressibility of the liquid in calculation of the process of the filling of a pipeline with local resistances, With the approach of the liquid to a local resistance, the hydraulic resistance changes sharply and there arise jumps of the pressure and the velocity. The fluctuations of the pressure and the velocity after filling of a section of the pipeline with a local resistance with a liquid can be calculated using the one-dimensional equations of the not fully established motion of a weakly compressible liquid in a cylindrical pipeline [3]

In vacuum and cryogenic engineering it is very important to determine the emissivities of insulating materials at low temperatures (T < 500~ The special features of measuring the emissivity c for such a material over a wide temperature range are related mainly to the methods of measuring the temperatures and radiation fluxes. It has been shown [i] that correct surface temperature measurement for an insulating specimen by contact methods requires the temperature transducer and its mounting elements to have the same emissivity as the surface, which is virtually impossible in many cases. Optical methods are used to measure s for insulating materials at high temperatures [2, 3] but are virtually inapplicable at low ones. Also, the low density E of the radiation fluxes resulting from s at low temperatures make it particularly necessary to eliminate radiation backgrounds in the measurement zone.