| 摘要 |
<PICT:1072993/C4-C5/1> A light beacon, e.g. on a buoy, comprises a light source in the form of a radio - luminescent lamp (10), and an optical system by means of which rays of light from the lamp are formed into a cylindrical beam. The housing may include material to reduce the radio-active emission to a safe level in the vicinity of the emergent beam, Fig. 1 (not shown), or may be so shaped that protection is given by the depth of water above the bulb, Figs. 3-6 (not shown). The light source comprises a bulb 12, Fig. 2, coated with a luminescent material and filled with a radio-active gas, e.g. krypton 85 or tritium. The bulb is held in position by means of a screw 46. Instead of gas a solid radioactive material e.g. caesium 137, strontium 90, or promethium may be mixed with the luminescent material. |
