Development of Lambertson Magnet and Septum Magnets for Splitting 30-GeV Proton Beam in Hadron Experimental Facility at J-PARC

Abstract

We developed a Lambertson magnet and two septum magnets as the splitting devices for the new beamline at the Hadron Experimental Facility in J-PARC. This new beamline, now under construction, is called high-p/COMET beamline, and the experiments using 30- and 8-GeV proton beams are planned. The required functions of the splitting devices are as follows: to split a small fraction (around 10−4) of the 30-GeV proton beam into the high-p/COMET beamline (30-GeV mode) and to bend all of the 8-GeV proton beam into the high-p/COMET beamline (8-GeV mode). These two requirements are met by adjusting the vertical beam position at the entrance of the Lambertson magnet. In 30-GeV mode, the Lambertson magnet is used to scrape the beam halo of the proton beam and bend the beam into the high-p/COMET beamline. The beam loss at the Lambertson magnet is inevitable; thus, the magnet must be resistant to the radiation and heat caused by the beam loss. The magnet is composed of nonorganic materials only and equipped with two water pipes to remove the heat induced by the beam loss. The branched beam is bent further by two septum magnets at the downstream of the Lambertson magnet. The construction and the magnetic field measurements of these devices were completed in March 2015, and the installation into the beamline is planned for the summer of year 2017.