page_title: Antiproton Accumulator
section_title: Operation
hierarchical_section_title: Antiproton Accumulator / Operation
caption_attribution_description: English: Overview of the Antiproton Accumulator (AA) at CERN
context_page_description: The Antiproton Accumulator was an infrastructure connected to the Proton–Antiproton Collider – a modification of the Super Proton Synchrotron – at CERN. The AA was built in 1979 and 1980, for the production and accumulation of antiprotons. In the SppS the antiprotons were made to collide with protons, achieving collisions at a center of mass energy of app. 540 GeV. Several experiments recorded data from the collisions, most notably the UA1 and UA2 experiment, where the W and Z bosons were discovered in 1983.
  The concept of the project was developed and promoted by C. Rubbia, for which he received the Nobel prize in 1984. He shared the prize with Simon van der Meer, whose invention of the method of stochastic cooling made large scale production of antiprotons possible for the first time.
context_section_description: Antiprotons were produced by directing an intense proton beam at a momentum of 26 GeV/c from the Proton Synchrotron (PS) onto a target for production. The emerging burst of antiprotons had a momentum of 3.5 GeV/c, and was selected via a spectrometer, and injected into the AA. The produced antiprotons would have a substantial momentum spread, which was decreased during a 2 s orbit around the AA, using Simon van der Meers method of stochastic cooling. The antiprotons were then trapped using a radiofrequency system, and moved inwards in the orbit to a stacking region. A next burst of antiprotons arrived 2.4 s (the PS cycle time) after the preceding one. This process was repeated during the whole accumulation period, which took about a day. The most intense stack, obtained after many days, would typically contain 5.2·10¹¹ antiprotons.
  The dense core of antiprotons was then ejected from the AA, and accelerated to 26 GeV/c, using the PS. Three antiproton bunches were consecutively transferred to the SppS, every 2.4 s. Just before the antiproton transfer, the PS would already have accelerated and transferred three proton bunches circulating the opposite direction to the antiprotons. When three bunches of antiprotons and three bunches of protons have filled the SppS, the bunches were accelerated to 315 GeV, and the beams were circulated for hours. During this time the AA continued to accumulate, to be ready for the next day's transfer.
caption: Overview of the Antiproton Accumulator (AA) at CERN
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