in the rutherford scattering experiment source of alpha particles is simply shown as a box. i want to know is there any type of experimental setup in the box or not? explain

why were alpha particles passes through a disc of lead.?

In rutherford's experiment of scattering of alpha particles , in the box there is an radioactive source from which alpha particles are coming out in the form of radiations due to radioactive decay.

 And since he required the fine beam of alpha particles to be fired on thin gold foil ,therefore he passed the radiations through a lead disc and actually the box is a lead block which absorbs the undirectional rays of alpha particles to convert it into a beam