Basic study on delta ray detection for the determination of In-Ring revolution time

An in-ring beam monitor for stored single ions is being developed at the Rare-RI Ring facility. The prototype utilizes high-energy secondary electrons, known as delta rays, produced at a thin foil in the periodic beam passage, and the revolutions of the stored ions were successfully observed. The aim of the present study is to improve the precision of the revolution time. The secondary electrons were systematically detected with a fast plastic scintillation counter by changing the distance from the foil and by changing the emission angle relative to the beam axis. The measured time resolutions were below 100 ps for a 200-MeV/nucleon ⁸⁴Kr beam. (author)