Antihydrogen Trapped

In 2010 the ALPHA collaboration succeeded in trapping antihydrogen atoms for the first time.\footnote{``Trapped antihydrogen,'' G.B. Andresen \textit{et al}., \textit{Nature} 468, 673 (2010)} Stored antihydrogen promises to be a unique tool for making high precision measurements of the structure of this first anti-atom. Achieving this milestone presented several substantial experimental challenges and this talk will describe how they were overcome. The unique design features of the ALPHA apparatus will be explained.\footnote{``A Magnetic Trap for Antihydrogen Confinement,'' W. Bertsche \textit{et al}., \textit{Nucl. Instr. Meth. Phys. Res. A} 566, 746 (2006)} These allow a high intensity positron source and an antiproton imaging detector similar to the one used in the ATHENA\footnote{``Production and detection of cold antihydrogen atoms,'' M.Amoretti \textit{et al}., \textit{Nature} 419, 456 (2002).} experiment to be combined with an innovative magnet design of the anti-atom trap. This seeks to minimise the perturbations to trapped charged particles which may cause particle loss and heating.\footnote{``Antihydrogen formation dynamics in a multipolar neutral anti-atom trap.'' G.B. Andresen \textit{et al., Phys. Lett. B} 685, 141 (2010)} The diagnostic techniques used to measure the diameter, number, density, and temperatures of both plasmas will be presented as will the methods developed to actively compress and cool of both plasma species to sizes and temperatures\footnote{``Evaporative Cooling of Antiprotons to Cryogenic Temperatures,'' G.B. Andresen \textit{et al}. \textit{Phys. Rev. Lett} 105, 013003 (2010)}$^,$\footnote{``Compression of Antiproton Clouds for Antihydrogen Trapping,'' G. B. Andresen \textit{et al}. \textit{Phys. Rev. Lett} 100, 203401 (2008)}$^,$\footnote{``Autoresonant Excitation of Antiproton Plasmas,'' G.B. Andresen \textit{et al}., \textit{Phys. Rev. Lett.} 106, 025002 (2011)} where trapping attempts with a reasonable chance of success can be tried. The results of the successful trapping experiments will be outlined as well as some subsequent experiments to improve the trapping rate and storage time.