| 摘要 |
A collimator for defining a radiation field of a high energy beam (1) emitted by a source along a beam axis (4). The collimator comprises two pairs of jaws. One pair of jaws (13, 14) is disposed on top of the other pair (16, 17) and staggered by 90 DEG against it so that a closed passageway for the beam is defined. Each jaw has an outer (18, 19, 21, 22) and an inner part (23, 24, 26). The inner part is inserted in the outer part and rotatable such that its inner surface, which defines one sidewall of the passageway, is tilted against the beam axis (4). The jaw is laterally shiftable, and both motions are coordinated so that when the jaw moves, its sidewall-defining surface is always aligned with the geometric divergency of the beam (1).
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