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Stimuli responsive polymersomes: Small Angle Neutron Scattering studies
May 27 14:30 - 15:30
- Diblock copolymers can self-assemble in solution in stable and robust polymersomes (vesicles),...
To deuterate or not to deuterate? That is the question
June 03 14:30 - 15:30
- Accepted wisdom when performing diffraction experiments with neutrons is to deuterate the...
Static and dynamic properties of a strong-leg spin-ladder
June 17 14:30 - 15:30
- The AF S = 1/2 Heisenberg spin ladder belongs to the simplest quantum magnets, yet disclosing the...
The standard rabbit irradiation system (RPA) consists of six individual irradiation channels, which are mutually independent but are identical except for the height of their irradiation position in the moderator tank. This vertical staggering allows the selection of a thermal neutron flux density adapted to the problem in hand, the available range being from
- 5x1012cm-2s-1 to
All RPA handling procedures take place in a room (UJA05 29) set aside exclusively for this purpose. For irradiation in the RPA, small samples of at most approx. 10 cm3 are packaged in polyethylene capsules (so-called rabbits) and conveyed pneumatically (propellant gas: carbon dioxide) into the irradiation position. The conveying time for this procedure is a few seconds. To be able to apply a defined neutron dose, a minimum irradiation time of approx. 30 seconds thus has to be observed. The maximum irradiation period is approx. 5 hours; this is predetermined by the use of polyethylene as packaging material. Once irradiation is complete, the samples are conveyed back along the same path and in the same way; however, each individual, irradiated and therefore activated sample is stopped in a shielded decay position so the induced dose rate can be measured. Only once it has been established by measurement that the irradiated sample is handleable from the point of view of radiation protection, is it released for further conveying to the delivery station. Before the sample is transferred out of the RPA, its dose rate is measured again and an aerosol monitor is used to check that the irradiation has not caused any contamination of the RPA channel. The sample is then transferred out of the RPA and delivered to the customer in suitable packaging. Alternatively, the irradiated sample may be conveyed from the decay position to a transfer station, where it is repackaged and sent directly via a compressed air-operated conveyor tube to the adjoining Institute for Radiochemistry (RCM), one of the most frequent users of the RPA.
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