Carl Anderson´s 1932 Positron

On August 2, 1932 Carl Anderson found the track of a positive particle with a mass about the same as that for the electron when examining photos from the magnetic field cloud chamber he operated at Caltech. The positron was discovered and Anderson shared the 1936 Nobel Prize in physics for that. However, the 60 MeV positron track strangely enough went upwards through the chamber, a fact that so far has not been much discussed. In Anderson´s published papers (Science 76(1932)238, Phys. Rev. 43(1933)491, Nobel lecture 1936) or in modern textbooks this remarkable fact is not discussed in detail. In this presentation different possibilities to produce an upward going positron in Anderson´s chamber will be reviewed.