The alpha process, also known as the alpha ladder, is one of two classes of nuclear fusion reactions by which stars convert helium into heavier elements, the other being the triple-alpha process. The triple-alpha process consumes only helium, and produces carbon. After enough carbon has accumulated, the reactions below take place, all consuming only helium and the product of the previous reaction. E is the energy produced by the reaction, released primarily as gamma rays (γ). The abundance of alpha elements in stars is usually expressed in a logarithmic manner: ,