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The Oak Ridge National Laboratory is planning to build the Second Target Station (STS) at the Spallation Neutron Source (SNS). STS will host a suite of novel instruments that complement the First Target Station’s beamline capabilities by offering an increased flux for cold neutrons and a broader wavelength bandwidth. A novel neutron imaging beamline, named the Complex, Unique, and Powerful Imaging Instrument for Dynamics (CUPI2D), is among the first eight instruments that will be commissioned at STS as part of the construction project. CUPI2D is designed for a broad range of neutron imaging scientific applications, such as energy storage and conversion (batteries and fuel cells), materials science and engineering (additive manufacturing, superalloys, and archaeometry), nuclear materials (novel cladding materials, nuclear fuel, and moderators), cementitious materials, biology/medical/dental applications (regenerative medicine and cancer), and life sciences (plant–soil interactions and nutrient dynamics). The innovation of this instrument lies in the utilization of a high flux of wavelength-separated cold neutrons to perform real time in situ neutron grating interferometry and Bragg edge imaging—with a wavelength resolution of δλ/λ ≈ 0.3%—simultaneously when required, across a broad range of length and time scales. This manuscript briefly describes the science enabled at CUPI2D based on its unique capabilities. The preliminary beamline performance, a design concept, and future development requirements are also presented.

We report on measured neutron cross section data for super-cooled water and ice by time-of-flight neutron transmission imaging. In particular we demonstrate the use of high duty cycle time-of-flight (HDC-TOF) measurements to determine the local aggregate state of water with spatial resolution, by exploiting the neutron cross section dependence on the mobility of hydrogen atoms for long neutron wavelengths (> 4 Å). While one can envision many different applications for this method, one example is to provide insights into the freezing mechanism during the start-up of polymer electrolyte fuel cells from below zero degrees. Unlike for other wavelength selective measurements (e.g. Bragg edge imaging), only a limited wavelength resolution is required for this method. With a chopper setup with high duty cycle (30 %), we reached a high contrast-to-noise ratio (CNR) with a contrast between ice and super-cooled water of 8 %. To maximize the CNR, we optimized the duty cycle, pulse period and image processing parameters. Moreover, we present a theoretical framework for performing such optimization calculations, which can be used to maximize CNR for any beam line and any substances. For the optimization procedure presented in this publication, we used cross section values for ice and super-cooled water measured with high wavelength resolution using wavelength frame multiplication choppers. Our results show that the aggregate state of water of a sufficiently thick layer of water (> 0.5 mm) can be reliably determined for a small area (1 mm2 ) and with a reasonable short acquisition time of 5 minutes. Fil: Siegwart, Muriel Dorothea. Paul Scherrer Institut. Electrochemistry Laboratory; Suiza. Paul Scherrer Institut. Laboratory for Neutron Scattering and Imaging; Suiza Fil: Woracek, Robin. European Spallation Source ESS; Suecia Fil: Marquez Damian, Jose Ignacio. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Tremsin, Anton. University of California at Berkeley; Estados Unidos Fil: Manzi Orezzoli, Victoria. Paul Scherrer Institut. Electrochemistry Laboratory; Suiza Fil: Strobl, Markus. Paul Scherrer Institut. Laboratory for Neutron Scattering and Imaging; Suiza Fil: Schmidt, Treicy Johanna. Paul Scherrer Institut. Electrochemistry Laboratory; Suiza. Eidgenössische Technische Hochschule Zürich; Suiza. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Boillat, Pierre. Paul Scherrer Institut. Electrochemistry Laboratory; Suiza

Spin-Echo Modulated Small Angle Neutron Scattering (SEMSANS) in Time-of-Flight (ToF) mode has been shown to be a promising technique for measuring (very) small angle neutron scattering (SANS) signals and performing quantitative Dark-Field Imaging (DFI), i.e., SANS with 2D spatial resolution. However, the wavelength dependence of the modulation period in the ToF spin-echo mode has so far limited the useful modulation periods to those resolvable with the limited spatial resolution of the detectors available. Here we present our results of an approach to keep the period of the induced modulation constant for the wavelengths utilised in ToF. This is achieved by ramping the magnetic fields in the coils responsible for creating the spatially modulated beam in synchronisation with the neutron pulse, thus keeping the modulation period constant for all wavelengths. Such a setup enables the decoupling of the spatial detector resolution from the resolution of the modulation period by the use of slits or gratings in analogy to the approach in grating-based neutron DFI.

Micromachined silica microchannel plates (MCPs) under development have a number of advantages over standard glass MCPs and open completely new possibilities in detector technologies. In this article we present the results of our studies on the thermal properties of silica microchannel plates (sMCPs). Similar to standard glass microchanel plates the resistance of silica MCPs was measured to change exponentially with temperature with a negative thermal coefficient of -0.036 per degreesC, somewhat larger than that of standard glass MCPs. The resistance also decreases linearly with the applied voltage, with the voltage coefficient of -3.1x10(-4) V-1. With the knowledge of these two coefficients, our thermal model allows the calculation of the maximum voltage, which can be applied to a given MCP without inducing a thermal runaway. A typical 25 mm diam, 240 mum thick sMCP with 6 mum pores has to have the resistance larger than similar to30 MOmega to operate safely at voltages up to 800 V. With this model we can also calculate the time required for a given silica MCP to reach the point of thermal equilibrium after a voltage increase. We hope that the ongoing efforts on a proper modification of the sMCP semiconducting layer will lead to the production of new MCPs with a small negative or even a positive thermal coefficient, reducing the possibility of thermal runaways of low-resistance MCPs required for high count rate applications. (C) 2004 American Institute of Physics.

The measurements of the electron cloud footprints produced by a stack of microchannel plates (MCPs) as a function of gain, MCP-to-readout distance and accelerating electric field are presented. To investigate the charge footprint variation, we introduce a ballistic model of the charge cloud propagation based on the energy and angular distribution at the MCP output. We also simulate the Coulomb repulsion in the electron cloud, which is likely to cause the experimentally observed increase in the cloud size with increasing MCP gain. Calculation results for both models are compared to the charge footprint sizes measured both in our experiments with high rear-field values (∼200–900 V/mm) and in the experiments of Edgar et al. [Rev. Sci. Instrum. 60, 3673 (1989)] (accelerating electric field ∼30–130 V/mm).

High material penetration by neutrons allows for experiments using sophisticated sample environments providing complex conditions. Thus, neutron imaging holds potential for performing in situ nondestructive measurements on large samples or even full technological systems, which are not possible with any other technique. This paper presents a new sample environment for in situ high resolution neutron imaging experiments at temperatures from room temperature up to 1100 ◦C and/or using controllable flow of reactive atmospheres. The design also offers the possibility to directly combine imaging with diffraction measurements. Design, special features, and specification of the furnace are described. In addition, examples of experiments successfully performed at various neutron facilities with the furnace, as well as examples of possible applications are presented. This covers a broad field of research from fundamental to technological investigations of various types of materials and components. © 2015 AIP Publishing LLC.

The spatial resolution of high-accuracy microchannel plate (MCP) detectors has reached the values, where the so-called detector walk (or image blurring) may start to limit any further improvements. Image blurring with gain is studied in detail for detectors incorporating angular-biased MCPs. It was found that the presence of the pore bias at the output MCP results in a variation of the charge footprint position for events with different gains. Events with higher gains are shifted in the direction of the pore bias and the absolute value of this shift is directly proportional to the absolute value of the detector gain. Variation of the detector modal gain from 7.5×106 to 2.5×107 resulted in a ∼100 μm image offset for a 13°-biased MCP positioned at a distance of 8.5 mm from the anode with an accelerating rear field of 75 V/mm. We also extended our previous study of another type of detector walk associated with fluctuations of the accelerating rear field. Image displacements as functions of the rear accelerat...