Measurement of 181 MeV H− ions stripping cross-sections by carbon stripper foil

The stripping cross-sections of 181 MeV H− (negative hydrogen) ions by the carbon stripper foil are measured with good accuracy. The present experiment was carried out at the 3-GeV RCS (Rapid Cycling Synchrotron) of J-PARC (Japan Proton Accelerator Research Complex). The stripping cross-sections for different charge states, also known as electron loss cross-sections of H− ion, are denoted as σ−11, σ−10 and σ01, for both electrons stripping (H−→H+), one-electron stripping (H−→H0) and the 2nd-electron stripping (H0→H+) proceeding σ−10, respectively. We have established very unique and precise techniques for such measurements so as also to determine a foil stripping efficiency very accurately. The cross-sections σ−11, σ−10 and σ01 are obtained to be (0.002±0.001)×10−18cm2, (1.580±0.034)×10−18cm2 and (0.648±0.014)×10−18cm2, respectively. The presently given cross-sections are newly available experimental results for an incident H− energy below 200 MeV and they are also shown to be consistent with recently proposed energy (1/β2) scaled cross-sections calculated from the previously measured data at 200 and 800 MeV. The present results have a great importance not only at J-PARC for the upgraded H− beam energy of 400 MeV but also for many new and upgrading similar accelerators, where H− beam energies in most cases are considered to be lower than 200 MeV.