Masatoshi Arai is the Technical Coordinator at the European Spallation Source (ESS) in Lund, Sweden, and Professor Emeritus at the High Energy Accelerator Research Organization (KEK), Japan. He started his career in pulsed neutron scattering in 1978 at Tohoku University in Japan and completed his PhD at the KENS facility at the National Laboratory for High Energy Physics (KEK) between 1980-1983. After post-doctoral work at the IPNS facility in Argonne National Lab, USA, he returned to KEK and started to develop technology for the J-PARC project, which was constructed 2001-2008. Later, he worked at the ISIS Facility, UK, for the UK-Japan Collaboration and at Kobe University as an Associated Professor.