Circular track of 42 Meu positron in 12,000 gauss magnetic field. The path length of the positron track in this photograph is nearly 8 meters. Electron and positron spiral tracks seen in a cloud chamber at the Lawrence Berkeley Laboratory, California. The electron and positron started their lives at the bottom of the frame; they were generated by a gamma ray entering from the right. The positron, which is an electron with a positive charge, spirals (larger loops) towards the bottom left corner while the electron's smaller loops move upwards. The other tracks crossing the frame are also due to electrons and positrons created by gamma rays beyond the right hand edge of the frame; the electrons curl clockwise while the positrons curl counterclockwise. The cloud chamber, also known as the Wilson chamber, is a particle detector used for detecting ionizing radiation.