Detector requirements for the European spallation neutron source ESS

For probing the structure and dynamics of matter at an atomic, molecular and mesoscopic level neutron scattering and diffraction methods are of utmost importance. Suffering presently from relatively low source strengths, compared e.g. to X-ray investigations, neutron scattering methods will greatly benefit from the increase of the instantaneous flux, which will be attained at the next generation of pulsed spallation. neutron sources with several MW average beam power in the proton beam hitting the spallation target. In particular at ESS, the strongest of these sources, the thermal neutron flux will exceed the highest available today by about two orders of magnitude in comparison with generic instruments at ILL or ISIS. In addition, improved neutron optics can further enhance the flux on the sample by another factor 5-10. Hence, the count rate loads on the neutron detectors could rise by up to three orders of magnitude and typically by factors of 50-150; however, in more and more experiments intensity will be sacrificed by using small and even submillimeter samples. Consequently, the development of neutron detectors with higher counting rate capability, better time-of-flight and position resolutions and improved background is prerequisite for taking full advantage of the improved source strength. In this paper the detector requirements for ESS will be reviewed in comparison with the current state-of-the-art and with promising novel solutions.