Simplify the following text for a Grade 8 native English-speaking person.
Original: After graduating in 1920 he became engaged in research work at the Cavendish Laboratory , Cambridge , where the director , Sir Ernest Rutherford , had now engaged Chadwick .
Simplified: After graduating in 1920 he did research work at the Cavendish Laboratory , Cambridge . The director there was Sir Ernest Rutherford .