Development of intense beam of ultracold antiprotons

A. Kellerbauer, C. Canali, Andreas Fischer +1 more

直史 黒田

Dmitry V. Kosachiov

Y. Yamazaki

Recently, slow and ultra‐slow antiprotons are now available, which will open a new field of research in atomic physics as well as in related fields. In realizing this, the combination of an RFQD (Radio Frequency Quadrupole Decelerator) and a large multi‐ring trap (MRT) installed in a super‐conducting solenoid has been employed. Several million antiprotons have already been accumulated, and a mono‐energetic antiproton beam of 10 eV has been extracted and transported through a specially designed beam line. A couple of basic experiments which get feasible by the developments of ultra slow antiproton beam are discussed, which include ionization and antiprotonic atom formation processes and also to study spectroscopic nature of various meta‐stable antiprotonic atoms under single collision conditions. A so‐called cusp trap configuration is also discussed, which could for the first time synthesize intense spin‐polarized antihydrogen beams. At the same time, it could trap antihydrogen atoms for a macroscopic time.

H. A. Torii, Y. Nagata, H. Toyoda +6 more

Antiproton, the antiparticle of proton, is a unique projectile in the study of atomic collision physics, which can be treated theoretically either as a `negative proton' or a `heavy electron'. Atomic capture of an antiproton will result in formation of a highly excited exotic atom. Antiprotonic helium atom has been studied intensively by means of precision laser spectroscopy, which has led to a stringent determination of antiproton mass and charge to a level of ppb. Comparison of these values with those of proton gives one of the best tests of CPT invariance, the most fundamental symmetry in physics. However, the dynamic processes of antiproton capture remain unclarified, except for some indirect information given by those optical and X-ray observations. With an aim to produce an antiproton beam at atomic-physics energies for `pure' collision experiments, we have so far developed techniques to decelerate, cool and confine antiprotons in vacuo, using a sequential combination of the Antiproton Decelerator (AD) at CERN, a Radio-Frequency Quadrupole Decelerator (RFQD), and an electromagnetic trap. Our recent success in stable extraction of monoenergetic ultra-slow antiprotons, about 3×105 in number available every 5 minutes, has opened up the possibility to study ionization and atomic capture processes between an antiproton thus provided as a beam and an atom prepared in the form of a supersonic gas-jet target, at an unprecedented low energy from 10 eV to 1 keV under the single-collision condition. Our design and strategy of the cross-beam experiments are discussed.

Daniel González-Cuadra, Maciej Lewenstein, A. Bermúdez +3 more