Alpha particles

Beta rays were identified as streams of speeding electrons and gamma rays as electromagnetic radiation with shorter wavelengths and higher frequencies than X-rays. By firing alpha particles at glass and observing the resultant gas, Rutherford confirmed that alpha particles were related to, but not identical to, helium atoms.
 Ernest Rutherford and Johannes Hans Wilhelm Geiger England and Germany 1906 Alpha particles

Beta rays were identified as streams of speeding electrons and gamma rays as electromagnetic radiation with shorter wavelengths and higher frequencies than X-rays. By firing alpha particles at glass and observing the resultant gas, Rutherford confirmed that alpha particles were related to, but not identical to, helium atoms.