II. Beam Definition, Beam Direction, and Protection Problems
| Autor: | B. M. Wheatley, H. J. Hodt, E. W. Savage |
|---|---|
| Rok vydání: | 1953 |
| Předmět: |
Materials science
Field (physics) business.industry Aperture Right angle chemistry.chemical_element General Medicine Tungsten law.invention Brass Optics chemistry law visual_art visual_art.visual_art_medium Radiology Nuclear Medicine and imaging Tube (container) business Diaphragm (optics) Beam (structure) |
| Zdroj: | The British Journal of Radiology. 26:58-62 |
| ISSN: | 1748-880X 0007-1285 |
| DOI: | 10.1259/0007-1285-26-302-58 |
| Popis: | The target of the X-ray tube is enclosed in a massive lead cone at the open end of which are placed two sets of 2-inch thick blocks mounted at right angles (Fig. 2). These blocks form the usual type of adjustable diaphragm device for square and rectangular fields. The original ones were of lead which transmitted approximately 7 per cent. of the primary beam, and even more in places where they had brass inserts. They were replaced by blocks of G.E.C. heavy alloy (95 per cent. tungsten), and the method of mounting was modified to avoid brass inserts. The radiation escaping the outside edges of the blocks was lessened by reducing the maximum aperture, limiting the field to 22 × 18 cm. at 100 cm. focus-skin distance. A steel holder was added in which heavy alloy inserts could be fitted for defining circular fields (Fig. 3A) and grid fields (Fig. 3B). Thin perspex plates incorporated in these inserts removed the electrons produced by the X-ray beam glancing on their tapered apertures. These fields are used at ... |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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