Neutron Scattering Instrument Research Articles

Further Optimized Design of a Nested Rotate Sextupole Permanent Magnet Lens for the Focusing of Pulsed Neutrons

A compact nested rotate sextupole permanent magnet (Nest-Rot-SPM) lens was designed for the focusing of pulsed neutrons. It is based on the working conditions of the Very Small Angle Neutron Scattering (VSANS) instrument at the China Spallation Neutron Source (CSNS), and is expected to focus a neutron pulse from 6 Å to 10.5 Å, without chromatic aberration. Three hurdles must be addressed, i.e., the tremendous torque, the heat deposition, and the synchronization with the neutron pulse, respectively. The bore diameter and segment length of the lens are optimized using a formula analysis of the key parameters and model simulations of the torque and heat deposition. A twin torque canceling design is used to reduce the torque to one-third of its original value, or even lower. The goal of this project is to take the device into practical use in the VSANS at the CSNS.

A Study of Stray Neutron Field Measurements for the Neutron Scattering Instruments at CSNS

Stray neutrons might cause several negative impacts. However, it is usually difficult to conduct precise stray neutron simulations using the Monte Carlo method. Therefore, in this study, a measurement technique was proposed to study the stray neutrons experimentally inside the neutron scattering instruments at China Spallation Neutron Source (CSNS). The adopted measurement instruments comprise an extended-range Bonner sphere spectrometer and a commercial neutron ambient-dose-equivalent dosimeter, which enables us to directly measure the neutron spectra and ambient-dose equivalent H*(10) values. Verification experiments were performed inside the BL06 beam line experimental area at CSNS at two exposed locations with different sample conditions. Comparison of the experimentally measured neutron spectra, integral neutron fluence, and H*(10) value with the simulations demonstrated the feasibility of using the proposed method for studying stray neutrons for the neutron instruments.

Web Applications for Neutron Scattering Instruments in MLF of J-PARC

Web Applications for Neutron Scattering Instruments in MLF of J-PARC

Technical Specification of the Small-Angle Neutron Scattering Instrument SKADI at the European Spallation Source

Small-K Advanced DIffractometer (SKADI is a Small-Angle Neutron Scattering (SANS) instrument to be constructed at the European Spallation Source (ESS). SANS instruments allow investigations of the structure of materials in the size regime between Angstroms up to micrometers. As very versatile instruments, they usually cater to the scientific needs of communities, such as chemists, biologists, and physicists, ranging from material and food sciences to archeology. They can offer analysis of the micro- and mesoscopic structure of the samples, as well as an analysis of the spin states in the samples, for example, for magnetic samples. SKADI, as a broad range instrument, thus offers features, such as an extremely flexible space for the sample environment, to accommodate a wide range of experiments, high-flux, and optimized detector-collimation system to allow for an excellent resolution of the sample structure, short measurement times to be able to record the internal kinetics during a transition in the sample, as well as polarized neutron scattering. In this manuscript, we describe the final design for the construction of SKADI. All of the features and capabilities presented here are projected to be included into the final instrument when going into operation phase.

Fabrication and testing of high-performance all-metal neutron guides and axisymmetric mirrors by electrochemical replication

ABSTRACTNeutron scattering is one of the most useful methods of studying the structure of matter, with applications to biomedical, structural, magnetic and energy-related materials. Neutron-scattering instruments are installed around research reactors or accelerator-based neutron sources, and neutron guides are critical components of these facilities. They are neutron-transport optical devices consisting of state-of-the-art mirrors often tens of meters long. Here we demonstrate a novel fabrication method of all-metallic neutron guides and axisymmetric mirrors by electroplating from precision mandrels. The process allows for the fabrication of single-piece all-metal guides of prismatic and axisymmetric shapes. We also demonstrate supermirror guides and axisymmetric focusing supermirrors produced with the same technology. We present the fabrication and tests of the multilayer-coated replicated guides and optic and show that the mandrel is reproduced with high fidelity and reliability. Such supermirror optics will provide game-changing improvements in neutron techniques.

Monte Carlo simulations of the S-shaped neutron guide

Neutron transport along guides is governed by the Liouville theorem and the technology involved has advanced in recent decades. Computer simulations have proven to be useful tools in the design and conception of neutron guide systems in facilities. In this study, we use a Monte Carlo method to perform simulations for an S-shaped neutron guide with different dimensions for a Small-Angle Neutron Scattering (SANS) instrument, through the MCSTAS software. A wavelength cutoff is observed and shown to be dependent on the geometrical parameters of the guide. Results for the neutron flux at sample position are presented and greater sensitivity of cutoffs concerning the curvatures of the guides than to their lengths is noticed. Our results are in agreement with those obtained from the Acceptance Diagram method and we analyse the beam divergence behaviour along the S-shaped guide.

Development of the PHITS Code and its Application to the Optimum Shielding Design for Neutron Scattering Instruments

Development of the PHITS Code and its Application to the Optimum Shielding Design for Neutron Scattering Instruments

Adding new capabilities to a neutron-scattering instrument to provide enhanced materials imaging

New modality introduces energy-resolved imaging to existing facility in Australia.

Background issues encountered by cold-neutron chopper spectrometer AMATERAS

Details of the background, that is, “unwanted signals accumulated by the data acquisition system of neutron instruments,” observed by the cold-neutron chopper spectrometer AMATERAS installed at the Materials and Life Science Experimental Facility at J-PARC are reported. In the design phase of AMATERAS, we carefully considered the achievement of high signal-to-noise ratio, and possible countermeasures were implemented. Actually, recent scientific outputs from AMATERAS indicates that the spectrometer is one of excellent neutron instruments with low background. In spite of that, in nine years of AMATERAS operation, we have encountered unwanted signals due to various reasons, including γ rays emitted at materials on or near the beam line including the sample itself, scattered neutrons from the beam line devices, air scattering, electronic noise in data acquisition system, cosmic rays, T0 burst, and other unknown sources. In this report, we discuss the background observed by AMATERAS, especially in the conditions of without samples, comprehensively. The possible sources of these signals and the countermeasures considered against the above sources are discussed, which may be helpful to those who are engaged in other existing or planned neutron-scattering instruments.

Energy-resolved neutron imaging options at a small angle neutron scattering instrument at the Australian Center for Neutron Scattering.

Energy-resolved neutron imaging experiments conducted on the Small Angle Neutron Scattering (SANS) instrument, Bilby, demonstrate how the capabilities of this instrument can be enhanced by a relatively simple addition of a compact neutron counting detector. Together with possible SANS sample surveying and location of the region of interest, this instrument is attractive for many imaging applications. In particular, the combination of the cold spectrum of the neutron beam and its pulsed nature enables unique non-destructive studies of the internal structure for samples that are opaque to other more traditional techniques. In addition to conventional white beam neutron radiography, we conducted energy-resolved imaging experiments capable of resolving features related to microstructure in crystalline materials with a spatial resolution down to ∼0.1 mm. The optimized settings for the beamline configuration were determined for the imaging modality, where the compromise between the beam intensity and the achievable spatial resolution is of key concern.

New search for mirror neutron regeneration

The possibility of relatively fast neutron oscillations into a mirror neutron state is not excluded experimentally when a mirror magnetic field is considered. Direct searches for the disappearance of neutrons into mirror neutrons in a controlled magnetic field have previously been performed using ultracold neutrons, with some anomalous results reported. We describe a technique using cold neutrons to perform a disappearance and regeneration search, which would allow us to unambiguously identify a possible oscillation signal. An experiment using the existing General Purpose-Small Angle Neutron Scattering instrument at the High Flux Isotope Reactor at Oak Ridge National Laboratory will have the sensitivity to fully explore the parameter space of prior ultracold neutron searches and confirm or refute previous claims of observation. This instrument can also conclusively test the validity of recently suggested oscillation-based explanations for the neutron lifetime anomaly.

Detector rates for the Small Angle Neutron Scattering instruments at the European Spallation Source

Building the European Spallation Source (ESS), the most powerful neutron source in the world, requires significant technological advances at most fronts of instrument component design. Detectors are not an exception. The existing implementations at current neutron scattering facilities are at their performance limits and sometimes barely cover the scientific needs. At full operation the ESS will yield unprecedented neutron brilliance. This means that one of the most challenging aspects for the new detector designs is the increased rate capability and in particular the peak instantaneous rate capability, i.e. the number of neutrons hitting the detector per channel, pixel or cm2 at the peak of the neutron pulse. This paper focuses on estimating the incident and detection rates that are anticipated for the Small Angle Neutron Scattering (SANS) instruments planned for ESS. Various approaches are applied and the results thereof are presented.

Progress on The Time-of-Flight Ultra Small Angle Neutron Scattering Instrument at SNS

We describe the Time-of-Flight (TOF) Ultra Small Angle Neutron Scattering (USANS) instrument at the Spallation Neutron Source, Oak Ridge National Laboratory (SNS, ORNL), which is now operating. The instrument, a double-crystal diffractometer (DCD), consists of a pair of triple-bounce symmetrically Bragg-reflecting Si(220) channel-cut crystals with a nominal Bragg angle of 70°, based on the Bonse-Hart multi-bounce concept. We briefly describe the instrument, present the results of measurements of double-crystal rocking curves, and exhibit a few early scientific results.

Design of multi-pinhole collimator system for SANS based on CPHS neutron source

A new design for Small Angle Neutron Scattering instrument based on utilization of multi-pinhole collimator is presented. The 7-pinhole structure has been proposed for 30 years by Glinka[1]. But due to the crosstalk issue, the SNR is not as high as traditional single pinhole system. Luckily, software nowadays helps us to analyze the system and optimize the parameters of the collimator. With the help of 7-pinhole collimator instead of single-pinhole, we can approach almost one magnitude higher flux than before, which is valuable especially in compact pulsed neutron source, whose flux is a big issue.

Neutron Scattering Measurements of Carbon Dioxide Adsorption in Pores within the Marcellus Shale: Implications for Sequestration.

Shale is an increasingly viable source of natural gas and a potential candidate for geologic CO2 sequestration. Understanding the gas adsorption behavior on shale is necessary for the design of optimal gas recovery and sequestration projects. In the present study neutron diffraction and small-angle neutron scattering measurements of adsorbed CO2 in Marcellus Shale samples were conducted on the Near and InterMediate Range Order Diffractometer (NIMROD) at the ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory along an adsorption isotherm of 22 °C and pressures of 25 and 40 bar. Additional measurements were conducted at approximately 22 and 60 °C at the same pressures on the General-Purpose Small-Angle Neutron Scattering (GP-SANS) instrument at Oak Ridge National Laboratory. The structures investigated (pores) for CO2 adsorption range in size from Å level to ∼50 nm. The results indicate that, using the conditions investigated densification or condensation effects occurred in all accessible pores. The data suggest that at 22 °C the CO2 has liquid-like properties when confined in pores of around 1 nm radius at pressures as low as 25 bar. Many of the 2.5 nm pores, 70% of 2 nm pores, most of the <1 nm pores, and all pores <0.25 nm, are inaccessible or closed to CO2, suggesting that despite the vast numbers of micropores in shale, the micropores will be unavailable for storage for geologic CO2 sequestration.

Intermediate-angle Neutron Scattering Instrument for Quantitative and Non-destructive Characterization of Nanostructures in Steels and Other Alloys

Intermediate-angle Neutron Scattering Instrument for Quantitative and Non-destructive Characterization of Nanostructures in Steels and Other Alloys

New Very Small Angle Neutron Scattering (VSANS) Instrument

The design of a new Very Small Angle Neutron Scattering (VSANS) Instrument for use in National Institute of Standards And Technology (NIST) will be discussed. This instrument is similar to a shorter instrument we designed and delivered to ANSTO in Australia called the Bilby SANS instrument. The NIST VSANS and the ANSTO Bilby SANS instruments have very similar dimensions for length and diameter and have similar requirements for internal detector motion, top access port, walkway supports, and ports; however, the Bilby SANS instrument vacuum requirement was lower (7.5×10-5 Torr) and the entire (60,000 pound) vessel was required to move 1.5 meters on external rails with a repeatability of 100 um, which ADC achieved. The NIST VSANS length is 24 meter, internal diameter 2.3 meter with three internal carriages.The NIST VSANS instrument, which covers the usual SANS range will also allow configuration to cover the range between q ∼⃒ 10-4 A-1 to 10-3 A-1 with a sample beam current of (104 neutrons/s). The key requirements are a second position-sensitive detector system having a 1 mm pixel size and a longer sample-detector flight path of 20 m (i.e., a 40 m instrument).

BILBY: Time-of-Flight Small Angle Scattering Instrument

The BILBY Time-of-Flight (ToF) Small Angle Neutron Scattering (SANS) instrument at the Bragg Institute at ANSTO is among a number of recent additions to the current suite of operating instruments. ...

Colloid Research on the Small and Wide Angle Neutron Scattering Instrument TAIKAN at MLF/J-PARC

Colloid Research on the Small and Wide Angle Neutron Scattering Instrument TAIKAN at MLF/J-PARC

Large-scale scientific facility at China Advanced Research Reactor for neutron scattering

As a complementary role to X-rays, neutrons provide a unique, non-destructive method. Neutron scattering techniques have been widely applied to the determination of the structural details and the dynamics of atomic arrangements in materials and matters. Large-scale scientific facility of neutron scattering has played an important role in basic research and industry. This paper reviews the outstanding characteristics of neutron probe, the development status of neutron scattering facilities abroad, and especially the progress of the first phase of Neutron Scattering Project at China Advanced Research Reactor (CARR). By now, ten instruments, including a High Resolution Powder Diffractometer (HRPD), a High Intensity Powder Diffractometer (HIPD), a Residual Stress Diffractometer (RSD), a texture diffractometer (TD), a four circle diffractometer (FC), two Triple Axis Spectrometers (TAS), a reflectometer (RF), a Small Angle Neutron Scattering instrument (SANS) and a High Frame-rate Neutron Imaging Test Station (HFNIT) have been constructed in cooperation with Peking University, Institute of Chemistry of Chinese Academy of Sciences (CAS), Institute of Physics of CAS, Juelich Center in Germany and the partner from Sweden. The construction of them has been completed and they are under commissioning. CARR has run more than 200 hours for adjusting and optimizing the instruments and some promising experimental results have been attained. As one of the most powerful high-flux reactor neutron sources in the world, CARR will ensure the development and application of neutron scattering in China.