The Collaborative International Dictionary of English v.0.48:

Lenard rays \Le*nard" rays\n. (Physics.)
   Rays emanating from the outer surface of a plate composed of
   any material permeable by cathode rays, as aluminium, which
   forms a portion of a wall of a vacuum tube, or which is
   mounted within the tube and exposed to radiation from the
   cathode. Lenard rays are similar in all their known
   properties to cathode rays. So called from the German
   physicist Philipp Lenard (b. 1862), who first described them.
   [Webster 1913 Suppl.]