The electrons are ejected before mixing the antiprotons with positrons. The ALPHA experiment combines positrons with antiprotons to study properties of antihydrogen. A very small fraction are stable particles of antimatter, such as positrons or antiprotons. The antiprotons were created by the "Antiproton Source". Cosmic ray antiprotons also have a much higher energy than their normal-matter counterparts (protons). Cosmic ray antiprotons also have a much higher average energy than their normal-matter counterparts (protons). The other method involves putting antiprotons and protons into the same magnetic cage. Iridium is used in particle physics for the production of antiprotons, a form of antimatter. The biggest limiting factor in the large-scale production of antimatter is the availability of antiprotons. It is then ionized into antiprotons which can be electromagnetically accelerated into the reaction chamber. In addition to antibaryons, anti-nuclei consisting of multiple bound antiprotons and antineutrons have been created. The secondary antiprotons () then propagate through the galaxy, confined by the galactic magnetic fields. CERN expects their facilities will be capable of producing 10 million antiprotons per minute. The catching trap slows, traps, cools, and accumulates antiprotons. The antiprotons are still hot when initially trapped.