| 摘要 |
<p>An irradiation appts. incorporates a source of radiation, a carrier for the source, a protective shield and a system for rotating the support into positions in which the source radiates, and does not radiate, successively and a system of immobilising the support in one or the other position for a predetermined time. The source may be a radioisotope e.g. Co 60 or Cs 137 or another natural or artificial radioactive element. The support is a disc with a cell at its periphery opening towards the outside, and placed inside the protective shield. The rotation system consists of a shaft at the centre of the disc and perpendicular to it, a drum fixed coaxially on the shaft, a tubular key, capable of turning about the shaft, a toothed wheel fixed coaxially on the key. The toothed wheel can be immobilised by pawls. A spiral spring, around the shaft, has its inner end fixed to the toothed wheel and its outer and fixed to the drum. The spring can be put under tension by the key and allows sequential 180 degrees rotations of the support, always in the same sense. The system of immobilising the source is associated with the drum, which has two notches at 180 degrees on the periphery. It consists of a coil, an electrical feed circuit connected to the coil, a soft iron core within the coil and a spring. The core has a pin at one end which can engage in the nothces. The spring holds the pin against the drum when the coil is disconnected. The circuit consists of a source of potential, a time-switch and a micro-contact associated with the drum, closing the circuit for a predetermined time. The appts. is simple and can be used for small doses of irradiation over a long time. The sequential operation can be programmed.</p> |
