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There is a strong need to push forward developments in the storage and control of ultra-low-energy antiproton beams to enable important scientific research. To this end, a small electrostatic ring, and associated electrostatic acceleration section, is being designed and developed by the QUASAR group. The ring will be placed on the MUSASHI beamline at the CERN-AD. It will serve as a prototype for the future ultra-low energy storage ring (USR), to be integrated at the facility for low-energy antiproton and ion research (FLAIR) and will enable various components of the USR to be tested and optimised. A reaction microscope will be integrated in the ring to enable partial ionisation cross section measurements to be made. This small recycler ring will be unique due to its combination of size, electrostatic nature and energy and type of circulating particles (ca 3-30 keV antiprotons). A short electrostatic accelerating section is also being developed, which will be placed between the beamline and the ring to accelerate the antiprotons from the trap extraction energy (typically 250 eV) to the final required (re-circulating) energy. The AD recycler project will be described, including ring design, accelerating injection section and the inclusion of a reaction microscope and the experiments it will enable. [ABSTRACT FROM AUTHOR]

Abstract: Here we present experimental information on the cross section for double ionization of helium atoms by slow antiproton impact. It is used to discern between many advanced theoretical calculations. Earlier measurements of the ratio R between the double and single ionization cross sections for antiproton impact on helium show a persistent increase for the projectile energy decreasing from 10MeV to 10keV. The present data show that below 10keV this increase stops and we give an upper limit to R. [Copyright &y& Elsevier]

The slowing-down process of point-like charged particles in matter has been investigated by measuring the energy straggling for antiprotons and protons in Al, Ni and Au. A comparison with binary theory shows good agreement for Al and Au. For Ni, experimental data are not as convincing. In particular for the aluminum target, the Barkas-like effect of reduced energy straggling for antiprotons compared to protons is visible in the experimental data and a nearly velocity-proportional straggling is found, in good agreement with binary theory. [ABSTRACT FROM AUTHOR]

We present experimental results for channeling of 1.4 MeV antiprotons in a 0.5 μm thick 〈1 0 0〉 silicon crystal. The ‘half-widths’ for the observed channeling effect, Δψp, is significantly smaller than the Lindhard angle, ψ1, as is the case for electrons where typical angles are about Δψe−≃0.6ψ1. In the case of protons and positrons, critical angles are of the order Δψe+≃Δψp≃ψ1. Thus, we may attribute the difference between Δψp,e− and Δψp,e+ to the sign of charge of the penetrating particle. [Copyright &y& Elsevier]