Americium and Radium mixed with Beryllium.
To transmute an atom, for example Th-232 to Th-233, we need some neutrons. It is here the α-emitter come into the picture. To get neutrons, just mix the α-emitter with Aluminum or Beryllium. Beryllium is the best, but it is pretty toxic, and Aluminum is easier to get.
An ampoule with Beryllium.
Why we need so much α-radiation is because of 1 MBq, there is only about 30 neutrons released (with Beryllium). The neutrons have to slows down with a moderator, which I will write about later. Neutron-radiation is ionizing, and the quality-factor depends on its energy;
< 10 keV = 5
10 keV - 100 keV = 10
100 keV - 2 MeV = 20
2 MeV - 20 MeV = 10
> 20 MeV = 5
As you see, it's more effective when the energy is in the middle. Neutrons can be hard to control, Because Lead or concrete won't stop it. But some other materials do, such as Cadmium, Boron, paraffin or graphite.
A neutron-gun. An old medicin-can, with a glass-pipe in the middle. Covered around with Lead.