The performance of ESS spectrometers in comparison with instruments at a short-pulse source

The performance of typical spectrometers at ESS, which is the first long pulse spallation source, has been compared with that of counterparts in J-PARC in a general fashion. The difference of the source nature results in a clear difference in the expected performance, in addition to that which can simply be expected from the difference in the source power. The article tries to show the advantages and disadvantages of the very different source character between ESS and J-PARC, and to make some suggestions on instrumentation to extract the full potential from them.