WordNet (r) 3.0 (2006):

beta ray
    n 1: radiation of beta particles during radioactive decay [syn:
         beta radiation, beta ray, electron radiation]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "beta ray":
   Becquerel ray, Grenz ray, Roentgen ray, X radiation, X ray,
   actinic ray, alpha radiation, alpha ray, anode ray, beta radiation,
   canal ray, cathode ray, cosmic radiation, cosmic ray,
   cosmic ray bombardment, electron emission, gamma radiation,
   gamma ray, infraroentgen ray, nuclear rays, positive ray,
   radiorays