Antihydrogen animations

• Creation of antiprotons

  This illustrates proton - proton collisions, in which pair production of many particles - among them proton-antiproton pairs - take place (click here)

• Capture of antiprotons

  Antiprotons are slowed down by passage through matter, and sufficiently slow antiprotons can be captured in an electromagnetic trap (click here) The blue surface symbolizes the electric trapping potential; as the cloud of antiprotons enters the trap region, the potential of the upstream region is raised. Those antiprotons that have insufficient energy to fly over the downstream potential hill will fall back, and also be unable to fly over the upstream potential hill, and are thus trapped. As long as the vacuum in which they are oscillating is sufficiently good, they can be held indefinately.

• Production of antihydrogen

  Captured antiprotons may combine with captured positrons to produce antihydrogen (click here) Since the resultant atom is neutral, it is no longer captured, and will fly onward, subject only to the force of gravity, emitting light quanta as it de-excites, until it encounters and annihilates on one of the electrodes that generate the electric fields in which antiprotons and positrons are held.

• Detection of antihydrogen

  Antihydrogen annihilation with matter is a two step process. Antiprotons annihilate on nuclei, producing charged (pions, nuclear fragments) and neutral (high energy photons) particles, while positrons annihilate with electrons, producing two back-to-back photons with an energy of exactly 511 keV. Charged particles can be detected in silicon detectors (red), while the 511 keV photons are detected in CsI crystals (light blue). This is an animated fly-through of the detector (click on any part of the detector to start the animation). The detector would see an antiproton annihilation like this (click on the detector to see only the annihilation products -- the detector will disappear).