Commissioning of the J-PARC K1.8 beamline and the beam spectrometer

Abstract

The K1.8 beam line of the J-PARC Hadron facility has been constructed for the experimental activities on hadrons and nuclei using secondary particles, especially kaon. On October 22nd 2009, the first beam was successfully extracted and the commissioning of the beam line and the experimental apparatus was started. Although the beam line was not tuned optimally, the yields of the beam kaon were measured to be at least 40 k for K+ and 5.1 k for K−, respectively, with the primary intensity of 2.5 × 1012protons. These values agreed with the designed ones within a few factors and will be improved after the fine tune. The momentum resolution of the beam spectrometer was estimated to be δp/p < 2.1 × 10−3 by the beam through run. Though it includes contributions from the spectrometers for scattered particles, it is satisfactory for the experiment.