We report here the first successful synthesis of cold antihydrogen atoms employing a cusp trap, which consists of a superconducting anti-Helmholtz coil and a stack of multiple ring electrodes. This success opens a new path to make a stringent test of the CPT symmetry via high precision microwave spectroscopy of ground-state hyperfine transitions of antihydrogen atoms.

Low energy antiprotons have been used previously to give benchmark data for theories of atomic collisions. Here we present measurements of the cross section for single, nondissociative ionization of molecular hydrogen for impact of antiprotons with kinetic energies in the range 2-11 keV, i.e., in the velocity interval of 0.3-0.65 a.u. We find a cross section which is proportional to the projectile velocity, which is quite unlike the behavior of corresponding atomic cross sections, and which has never previously been observed experimentally.

The ASACUSA collaboration developed an ultraslow antiproton beam source, monoenergetic ultraslow antiproton source for high-precision investigation (MUSASHI), consisting of an electromagnetic trap with a liquid He free superconducting solenoid and a low energy antiproton beam transport line. The MUSASHI was capable of trapping and cooling more than 1 Â 10 7 antiprotons and extracting them as an ultraslow antiproton beam with energy of 150-250 eV.

A new electrostatic ion storage ring, the RIKEN cryogenic electrostatic ring, has been commissioned with a 15-keV ion beam under cryogenic conditions. The ring was designed with a closed ion beam orbit of about 2.9 m, where the ion beam is guided entirely by electrostatic components. The vacuum chamber of the ring is cooled using a liquid-He-free cooling system to 4.2 K with a temperature difference of 0.4 K at most within all the positions measured by calibrated silicon diode sensors. The first cryogenic operation with a 15-keV Ne beam was successfully performed in August 2014. During the measurement, the Ne beam was stored under a ring temperature of 4.2 K with a residual-gas lifetime of more than 10 min. This permits an estimation of the residual gas density at a few 10 cm, which corresponds to a room-temperature-equivalent pressure of around 1×10 Pa. An effect of longitudinal pulse compression at the bunching cavity in the ring was clearly identified by monitoring the pick-up beam detector. The detailed design and mechanical structure of the storage ring, as well as the results from the commissioning run, are reported.

We demonstrate that transitions between Zeeman-split sublevels of Rb atoms are resonantly induced by the motion of the atoms (velocity: ∼ 100 m/s) in a periodic magnetostatic field (period: 1 mm) when the Zeeman splitting corresponds to the frequency of the magnetic field experienced by the moving atoms. A circularly polarized laser beam polarizes Rb atoms with a velocity selected using the Doppler effect and detects their magnetic resonance in a thin cell, to which the periodic field is applied with the arrays of parallel current-carrying wires.PACS numbers: 32.30. Dx, 32.80.Bx By applying an electromagnetic (EM) wave to an atom at rest, one can resonantly induce transition between two atomic energy levels whose frequency difference coincides with the EM wave frequency. This resonance transition is one of the most extensively studied and widely utilized phenomena in atomic physics and also in other various fields. Also in the reversed configuration, that is, by an atom moving in a static periodic field, an internal transition can be made when the periodic perturbation experienced by the atom has a frequency equal to the transition frequency. The resonance transition of this kind, quite simple in principle and applicable to any particle with internal states, however, has been clearly demonstrated only in the phenomenon called "resonant coherent excitation" (RCE) [1] using channeled fast ion beams in periodic electric fields of crystals. RCE has attracted much attention [2,3] since the first proposal by Okorokov [4]. Recent progress made by using the high-energy beams of highly charged ions shows the possibility of high resolution spectroscopy of highly charged ions in an x-ray region of keV or 10 18 Hz [5]. The order of this transition frequency is determined by an ion velocity (∼ 10 8 m/s) and a lattice constant (∼ 10 −10 m).We report in this Letter on the resonance transition that is based on the same principles as RCE but is induced by a different type of interaction in a quite different energy range of neV or 10 5 Hz: magnetic resonance between the Zeeman sublevels of Rb atoms with a z velocity component v z of ∼ 100 m/s in a static magnetic field that is periodic in the z direction (period: a = 1 mm). This resonance transition, called motioninduced resonance in this Letter, was observed in a thin cell containing Rb vapor, with the periodic magnetic field applied with the arrays of parallel current-carrying wires sandwiching the cell. The atoms with a velocity selected using the Doppler effect were polarized by optical pumping with circularly polarized laser light slightly detuned from the D 2 line. The magnetic resonance between the ground state sublevels was optically detected with the same laser beam. We confirmed that the resonance occurs when the Zeeman splitting frequency coincides with v z /a, namely the frequency of the field experienced by the moving atoms. We successfully obtained the resonance spectra very similar to those of standard rf magnetic resonance. Our clear demonstration of motion-ind...