cathode ray vs electron beam

cathode ray and electron beam both are nouns.

Word	Noun	Adjective	Verb	Adverb
cathode ray	Yes	No	No	No
electron beam	Yes	No	No	No

As nouns, electron beam is a hypernym of cathode ray; that is, electron beam is a word with a broader meaning than cathode ray:

cathode ray: a beam of electrons emitted by the cathode of an electrical discharge tube
electron beam: a group of nearly parallel lines of electromagnetic radiation

Other hypernyms of cathode ray include beam, ray.

cathode ray (noun)	electron beam (noun)
a beam of electrons emitted by the cathode of an electrical discharge tube	a group of nearly parallel lines of electromagnetic radiation