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Abstract
Development of accelerator-based neutron sources began after the 1970s, starting with electron accelerators using the bremsstrahlung photoneutron reaction. Now proton accelerators are the main drivers for neutron sources because of the efficiency of the spallation nuclear reaction for neutron yield (spallation source). Consequently, development of accelerator technology increases the power and neutron flux of spallation sources [1]. The pulsed nature of accelerator-based neutron sources in most cases can give large advantage in experiments using the time-of-flight (TOF) method. Moreover, because the heat dissipates slowly in the period between pulses the instantaneous power and neutron flux can be very high (thermal shock remains a problem to be overcome at the highest levels of proton power) [2]. Hence, building spallation neutron sources instead of reactors is becoming a world trend as demonstrated by the Spallation Neutron Source (SNS) in Oak Ridge, Tennessee (U.S.A.) and JSNS (what is called Japan Spallation Neutron Source) in the J-PARC, on which we describe here recent development. China has started construction of the China Spallation Neutron Source (CSNS), and quite recently a European Spallation Source (ESS) construction site has been decided on in Lund, Sweden after a tough bidding against Spain and Hungary.
Acknowledgments
The authors appreciate their colleagues at the Materials Life Science Division of J-PARC Center. Their support and cooperation have been indispensable for the construction and commissioning of the facility.