| 摘要 |
<p>A miniaturized, optically driven therapeutic radiation source (100) includes a laser-heated thermionic cathode (122). A fiber optic cable (113) directs a light beam from an optical source (104) to impinge upon a surface of the thermionic cathode (122), heating the surface to a temperature sufficient to cause thermionic emission of electrons. The target element (128) emits therapeutic radiation, such as x-rays, in response to incident accelerated electrons from the electron beam. In one embodiment, the electron source (122) and the target element (128) are disposed within a capsule (130) which defines a substantially evacuated region. The inner surface of the capsule is coated with a semiconductor coating, so that a uniform voltage gradient is maintained within the evacuated capsule. In another embodiment, the thermionic cathode (300) is formed of a spiral-shaped conductive element (310) having a plurality of spaced-apart turns. Interstitial spacing between adjacent turns essentially eliminates heat transfer across the spacin.</p> |
