| 摘要 |
<p>Apparatus for determining the density profile of a medium comprises a vertically disposed elongated member of a material transparent to η-radiation containing a plurality of sources of collimated beams of η-radiation of characteristic energy level below 100 keV and, for each beam, detector shielded from the sources by material transparent to the radiation. Each collimated beam is directed to irradiate a region external to said elongated member, and the detector associated with that beam is disposed to detect radiation scattered from said region by the medium.</p> |
