Various kinds of energetic particles are irradiated into iron-based superconductors, and their effects on the critical current density (J c ) and vortex dynamics have been systematically studied. It is found that J c is enhanced and vortex dynamics is strongly suppressed by energetic particles having a sufficient energy deposition rate, similar to the case of high temperature cuprate superconductors. The enhancement of J c , in general, persists up to much higher irradiation doses than in cuprates. However, details of the effect of irradiation depend on the kind of ion species and their energies. Even with the same ions and energies, the effect is not universal for different kinds of iron-based superconductors. The correlated nature of defects created by heavy-ion irradiation is confirmed by the angular dependence of irreversible magnetization.

Antihydrogen, a positron bound to an antiproton, is the simplest antiatom. Its counterpart—hydrogen—is one of the most precisely investigated and best understood systems in physics research. High-resolution comparisons of both systems provide sensitive tests of CPT symmetry, which is the most fundamental symmetry in the Standard Model of elementary particle physics. Any measured difference would point to CPT violation and thus to new physics. Here we report the development of an antihydrogen source using a cusp trap for in-flight spectroscopy. A total of 80 antihydrogen atoms are unambiguously detected 2.7 m downstream of the production region, where perturbing residual magnetic fields are small. This is a major step towards precision spectroscopy of the ground-state hyperfine splitting of antihydrogen using Rabi-like beam spectroscopy.

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.

The authors have developed a method to produce a microbeam of slow highly charged ions based on a self-organized charge-up inside a tapered glass capillary. A transmission of 8 keV Ar 8+ beam through the capillary 5 cm long with 800/ 24 m inlet/outlet inner diameters was observed stably for more than 1200 s. The transmitted beam had the same size as the outlet with a beam density enhancement of approximately 10 and a divergence of ±5 mrad. The initial beam was guided through a capillary tilted by as large as ±100 mrad, and it still kept the incident charge.

The transmission of highly charged ions through nanocapillaries in insulating polyethylene terephthalate ͑PET͒ polymers was investigated. In experiments at laboratories in RIKEN ͑Japan͒ and HMI ͑Germany͒ different detection methods were applied to study the ion current dependence in a wide range covering two orders of magnitude. At HMI an electrostatic ion spectrometer was used and at RIKEN a two-dimensional position sensitive detector was implemented. New PET samples with parallel capillaries and low density were manufactured. For tilted capillaries, the ions are guided along the capillary axis, since the majority of ions are deflected in a charge patch created in the capillary entrance. The results provide insights into the mechanisms of capillary guiding. The fraction of transmitted ions was found to be nearly independent on the incident ion current indicating a sudden increase in the discharge current depleting the entrance charge patch. The experimental results were well-reproduced by model calculations based on a nonlinear ͑exponential͒ expression for the discharge current.

The goal of the ASACUSA-CUSP collaboration at the Antiproton Decelerator of CERN is to measure the ground-state hyperfine splitting of antihydrogen using an atomic spectroscopy beamline. A milestone was achieved in 2012 through the detection of 80 antihydrogen atoms 2.7 m away from their production region. This was the first observation of ‘cold’ antihydrogen in a magnetic field free region. In parallel to the progress on the antihydrogen production, the spectroscopy beamline was tested with a source of hydrogen. This led to a measurement at a relative precision of 2.7×10−9 which constitutes the most precise measurement of the hydrogen hyperfine splitting in a beam. Further measurements with an upgraded hydrogen apparatus are motivated by CPT and Lorentz violation tests in the framework of the Standard Model Extension. Unlike for hydrogen, the antihydrogen experiment is complicated by the difficulty of synthesizing enough cold antiatoms in the ground state. The first antihydrogen quantum states scan at the entrance of the spectroscopy apparatus was realized in 2016 and is presented here. The prospects for a ppm measurement are also discussed.This article is part of the Theo Murphy meeting issue ‘Antiproton physics in the ELENA era’.

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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.