Production of ultra slow antiprotons, its application to atomic collisions and atomic spectroscopy-ASACUSA project

The atomic spectroscopy and collisions using slow antiprotons (ASACUSA) project aims at studying collision dynamics with slow antiprotons and high precision spectroscopy of antiprotonic atoms. To realize these purposes, the $9 production of high quality ultra slow antiproton beams is essential, which is achieved by the combination of antiproton decelerator (AD) from 3 GeV to 5 MeV, a radio frequency quadrupole (RFQ) decelerator from 5 MeV to 50 keV, and $9 finally an electromagnetic trap from 50 keV to 10 eV. From the atomic physics point of view, an antiproton is an extremely heavy electron and/or a negatively charged proton, i.e., the antiproton is a unique tool to shed light on $9 collision dynamics from the other side of the world. In addition to this fundamentally important feature, the antiproton has also a big practical advantage, i.e., it annihilates with the target nuclei emitting several energetic $9 pions, which provides high detection efficiency with very good time resolution. Many-body effects which are of great importance to several branches of science will be studied through ionization and antiprotonic atom formation $9 processes under single collision conditions. Various antiprotonic atoms including protonium (pp) are expected to be meta-stable in vacuum, which is never true for those in dense media except for antiprotonic helium. High precision $9 spectroscopy of protonium will for the first time become feasible benefited by this meta-stability. The present review reports briefly the production scheme of ultra slow antiproton beams and several topics proposed in the ASACUSA $9 project. (49 refs).