Beta-voltaics are generators of electrical current, in effect a form of battery, which use energy from a radioactive source emitting beta particles (electrons). Which of the following is the most commonly used source?

Betavoltaics are generators of electrical current that use energy from a radioactive source emitting beta particles (electrons). A common source used is the hydrogen isotope; tritium. Unlike most nuclear power sources (thermoelectric and thermionic sources), which use nuclear radiation to generate heat, are then used to generate electricity. Betavoltaics use a non-thermal conversion process; converting the electron-hole pairs produced by the ionization trail of beta particles traversing a semiconductor.