H. Imao

Positron accumulation and manipulation for antihydrogen synthesis

Our group ASACUSA-MUSASHI has established an efficient way for accumulating antiprotons in the cusp trap, a combination of an anti-Helmholz superconducting coil and a multi-ring electrode trap. The last piece for synthesizing antihydrogens in the cusp trap is positron. We have developed a compact system to effectively accumulate positrons based on N2 gas-buffer scheme with a specially designed high precision cylindrical multi-ring electrode trap. Millions of positrons were accumulated in the pre-accumulator just using polycrystalline tungsten moderators. The accumulated positrons were transported as a pulsed beam via three guiding coils and caught in the cusp trap under cryogenic and ultra high vacuum conditions without serious loss. Confinement of two kinds of numerous antiparticles, e.g., 108 positrons and 107 antiprotons, in the cusp trap becomes feasible.

Observation of Ultra‐Slow Antiprotons using Micro‐channel Plate

Our group ASACUSA‐MUSASHI has succeeded in accumulating several million antiprotons and extracting them as monochromatic ultra‐slow antiproton beams (10 eV–1 keV) at CERN AD. We have observed ultra‐slow antiprotons using micro‐channel plates (MCP). The integrated pulse area of the output signals generated when the MCP was irradiated by ultra‐slow antiprotons was 6 times higher than that by electrons. As a long‐term effect, we also observed an increase in the background rate presumably due to the radioactivation of the MCP surface. Irradiating the antiproton beams on the MCP induces antiproton‐nuclear annihilations only on the first layer of the surface. Low‐energy and short‐range secondary particles like charged nuclear fragments caused by the “surface nuclear reactions” would be the origin of our observed phenomena.

Towards the production of anti-hydrogen beams

Recently, the production of low energy anti-hydrogen atoms in the cusp trap with the use of 150eV antiproton beams from the MUSASHI trap was reported. The purpose of producing low energy anti-hydrogen atoms in a cusped magnetic field is to extract a polarized anti-hydrogen beam to a field free region, so that the hyperfine structure of anti-hydrogen atoms can be measured.

Radial compression of antiproton cloud for production of ultraslow antiproton beams

We report here the radial compression of a large number of antiprotons under ultrahigh vacuum conditions by applying a rotating electric field. The radial compression is a key technique for production of ultraslow antiproton beam extracting from an electromagnetic traps. Such beam will be applicable to synthesizing antiprotonic atoms and antihydrogen atoms.