What technology was available to Thomson that enabled him to make his discovery on atoms?

Answer 1

For what might be his most famous experiment, the refutation of Thomson's 'plum pudding' model, only limited apparatus was used: a source of positively charged alpha particles that would be deflected by atomic nuclei, some thin gold foil, a collimitor to narrow the beam of alpha particles, a zinc sulphide screen to register any alpha particles deflected by nuclei, and a microscope to render flashes on this screen visible to the naked eye. All in a darkened room. The various parts of the apparatus could be moved in an arc relative to one another to verify whether scattering of the alpha particles had occurred. Rutherford didn't like statistics but the results were unequivocal.

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Answer 2

The experiment is called alpha particle scattering. A radioactive alpha particle source (a thin glass tube of one mm diameter containing purified radium) was pointed towards a thin gold foil, and number of particles scattered through various angles was measured. The detector was a zinc sulfide screen, which flashes when an alpha particle hits it. They also used a microscope to observe the flashes.