Neutron detectors for the ESS diffractometers

Abstract

The ambitious instrument suite for the future European Spallation Source whose civil construction started recently in Lund, Sweden, demands a set of diverse and challenging requirements for the neutron detectors. For instance, the unprecedented high flux expected on the samples to be investigated in neutron diffraction or reflectometry experiments requires detectors that can handle high counting rates, while the investigation of sub-millimeter protein crystals will only be possible with large-area detectors that can achieve a position resolution as low as 200 µm. This has motivated an extensive research and development campaign to advance the state-of-the-art detector and to find new technologies that can reach maturity by the time the ESS will operate at full potential. This paper presents the key detector requirements for three of the Time-of-Flight (TOF) diffraction instrument concepts selected by the Scientific Advisory Committee to advance into the phase of preliminary engineering design. We discuss the detector technologies commonly employed at the existing similar instruments and their major challenges for ESS. The detector technologies selected by the instrument teams to collect the diffraction patterns are also presented. Analytical calculations, Monte-Carlo simulations, and real experimental data are used to develop a generic method to estimate the event rate in the diffraction detectors. We apply this method to make predictions for the future diffraction instruments, and thus provide additional information that can help the instrument teams with the optimisation of the detector designs.

Characterization of the Multi-Blade 10B-based detector at the CRISP reflectometer at ISIS for neutron reflectometry at ESS

“…The direct beam was directed to the lower cassette of the Multi-Blade detector without being reflected by any sample and its footprint, at the detector, was approximately 3 mm × 60 mm. The instantaneous peak rate (as defined in [14]) in the beam was of ≈ 10 4 Hz (corresponding to an instantaneous local rate of ≈ 50 Hz/mm 2 at peak). Note that if no software thresholds are applied nor the wires are requested to be in coincidence with the strips, a constant background is visible and it is mostly due to γ-rays.…”

“…The ToF spectra in Figure 12 is shown for the wires in the beam and for those in the tails. Above 8 ms, a difference of approximately 3 orders of magnitude in counting rate, in the same ToF bin, is visible between any wire in the interval [11][12][13][14][15][16][17][18][19] and any other in the tails (1-10 or 20-32). Moreover, the ToF spectrum varies of 3 orders of magnitude within two subsequent time bins (at ≈ 2 ms).…”

The Multi-Blade Boron-10-based neutron detector performance using a focusing reflectometer

“…The global time-averaged rate can be expressed as the total number of counts per second recorded in the total active area of the detector. The local instantaneous peak rate is defined as the highest instantaneous neutron count rate on the brightest detector pixel [20]. The full divergence of the beam, given by the geometry of the Selene guide, is ∆θ = 1.6 • .…”

Software-based data acquisition and processing for neutron detectors at European Spallation Source—early experience from four detector designs

“…Global avg. rate is defined in [10]. Data Rate is the corresponding amount of data received for software processing.…”