Nursing officer welcoming revolutionary English microwave source (9)

'microwave source' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?

'nursing officer welcoming revolutionary english' is the wordplay.
'nursing officer' becomes 'matron' (I've seen this before).
'welcoming' means one lot of letters goes inside another (in sense of 'inviting in').
'revolutionary' is a reversal indicator (letters revolve around).
'english' becomes 'eng' (abbreviation).
'eng' in reverse letter order is 'gne'.
'matron' placed around 'gne' is 'MAGNETRON'.

Can you help me to learn more?