6533b862fe1ef96bd12c6136

RESEARCH PRODUCT

The carrier-loaded helium-jet transport method

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Abstract The suitability of commercial helium loaded with small amounts of different gases or vapors for the transport of radioactive reaction products over distances of several meters has been investigated experimentally. Negative results were obtained with gaseous carriers. Transport efficiencies of 50 to 100% were obtained with carrier vapors. The vapor appears to form droplets in the system. The recoils are adsorbed physically by the droplets and carried with them through a capillary. There appears to be an active mechanism that forces the heavy constituents to the centre of the capillary cross section. The heavy constituents emerge from the capillary as a very narrow beam. Collection of the transported activity onto a metal foil in a vacuum chamber is possible only when the vapor pressure of the carrier is lower than the pressure of the collection chamber. Vacuum pump oil was found to meet this requirement. The transport and collection efficiency was studied as a function of the relative mass throughput of the oil vapor. A method for determining the optimum mass throughput of the carrier is demonstrated. The internal energetics of the system are discussed. The kinetic energy of a particle to be transported has to be higher than the average thermal energy in order to avoid adsorption onto the capillary walls. This can be achieved by increasing the mass of the particle by means of a carrier or by decreasing the system temperature. In a cooled system transport over long distances is possible even with pure helium. Application of the carrier-loaded transport method in on-line mass separators is discussed.