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.