Demonstration with very-cold neutrons of developments in Fourier time-of-flight Neulinger, Thomas; Bernert, Karina; Fierlinger, Peter ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
September 2024, 2024-09-00, Letnik:
1066
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We demonstrate recent developments in neutron Fourier time-of-flight in an experiment using very-cold neutrons. The implementation of a novel sinusoidal stator design eliminates a systematic effect ...associated with triangular modulation in existing Fourier choppers. Although transmission is inherently higher for triangular modulation, it is demonstrated that only about 3% additional measurement time is needed with sinusoidal modulation to achieve the same statistical uncertainty. In addition, a new neutron-based technique that does not require additional instrumentation is employed to determine the chopper phase offset.
The intensity of single‐crystal Bragg peaks obtained by mapping neutron time‐of‐flight event data into reciprocal space and integrating in various ways is compared. These methods include spherical ...integration with a fixed radius, ellipsoid fitting and integration of the peak intensity, and one‐dimensional peak profile fitting. In comparison to intensities obtained by integrating in real detector histogram space, the data integrated in reciprocal space result in better agreement factors and more accurate atomic parameters. Furthermore, structure refinement using integrated intensities from one‐dimensional profile fitting is demonstrated to be more accurate than simple peak‐minus‐background integration.
•Olive oil phenolic compounds profiling using LC–ESI–TOF MS and GC–APCI–TOF MS.•PCA facilitated visualisation of natural clustering of studied oils.•Reliable PLS-DA models for varietal discrimination ...of studied oils were established.•Potential varietal markers were identified.
Over the last decades, the phenolic compounds from virgin olive oil (VOO) have become the subject of intensive research because of their biological activities and their influence on some of the most relevant attributes of this interesting matrix. Developing metabolic profiling approaches to determine them in monovarietal virgin olive oils could help to gain a deeper insight into olive oil phenolic compounds composition as well as to promote their use for botanical origin tracing purposes. To this end, two approaches were comparatively investigated (LC–ESI–TOF MS and GC–APCI–TOF MS) to evaluate their capacity to properly classify 25 olive oil samples belonging to five different varieties (Arbequina, Cornicabra, Hojiblanca, Frantoio and Picual), using the entire chromatographic phenolic profiles combined to chemometrics (principal component analysis (PCA) and partial least square-discriminant analysis (PLS–DA)). The application of PCA to LC–MS and GC–MS data showed the natural clustering of the samples, seeing that 2 varieties were dominating the models (Arbequina and Frantoio), suppressing any possible discrimination among the other cultivars. Afterwards, PLS–DA was used to build four different efficient predictive models for varietal classification of the samples under study. The varietal markers pointed out by each platform were compared. In general, with the exception of one GC–MS model, all exhibited proper quality parameters. The models constructed by using the LC–MS data demonstrated superior classification ability.
Time-of-flight (ToF) single-photon avalanche diode (SPAD) arrays are an increasingly popular option for 3-D imaging. However, the traditional direct ToF (dToF) and indirect ToF (iToF) SPAD ranging ...pixels still struggle to get accuracies and precisions below the millimeter for short ranges. We propose to adapt the continuous-wave indirect ToF (cw-iToF) method to use eight integrating windows instead of the usual 4. This 8-windows cw-iToF method greatly reduces the nonlinearity error when using a square optical signal, which consequently enables its use at much higher frequencies than if a sine wave was required, while also showing great robustness to an imperfect square wave, unlike pulse indirect ToF (p-iToF). We provide an analysis of the effects of this new method on the accuracy and precision. Then, we present a single-pixel proof of concept implementation of an eight-taps cw-iToF SPAD pixel containing 4 up/down counters in a <inline-formula> <tex-math notation="LaTeX">0.18~\mu </tex-math></inline-formula> m CMOS process. Laser diodes illuminate the target with a 200 MHz square wave. The depth measurement's worst nonlinearity error over a 75 cm range is 1.2 mm, and stays below 1 mm for more than 90% of the measured range. Furthermore, the precision for 100 ms-long frames is as low as 0.35 mm.
A 256 × 256 single-photon avalanche diode (SPAD) sensor integrated into a 3-D-stacked 90-nm 1P4M/40-nm 1P8M process is reported for flash light detection and ranging (LIDAR) or high-speed direct ...time-of-flight (ToF) 3-D imaging. The sensor bottom tier is composed of a 64 × 64 matrix of 36.72-μm pitch modular photon processing units which operate from shared 4 × 4 SPADs at 9.18-μm pitch and 51% fill-factor. A 16 × 14 bit counter array integrates photon counts or events to compress data to 31.4 Mb/s at 30-frame/s readout over 8 I/O operating at 100 MHz. The pixel-parallel multi-event time-to-digital converter (TDC) approach employs a programmable internal or external clock for 0.56-560-ns time bin resolution. In conjunction with a per-pixel correlator, the power is reduced to less than 100 mW in practical daylight ranging scenarios. Examples of ranging and high-speed 3-D ToF applications are given.
Time-of-flight (ToF) sensors using light pulses or continuous waves allow accurate distance measurements. Three-dimensional imagers can be based on an array of timing or time-gated integration ...pixels. Single-photon avalanche diodes (SPADs) have been increasingly chosen as the pixel's photodetector device to develop fast, long-range ToF sensors. Solid-state ToF cameras are replacing other alternatives, showing attractive characteristics and bringing up new potential applications. This paper presents the technical evolution of SPAD ToF 3D imaging sensors, and provides insight into their development over the last few decades. Starting with the first SPAD imagers reported in the early 2000's, various direct and indirect arrays up to present day state-of-the-art prototypes are referenced. The existing methods, options and possible implementations are described, addressing their advantages and drawbacks, and showing the progress yet to be made. The performance of the different presented approaches are given and compared.
BILBY is a recently constructed and commissioned time‐of‐flight small‐angle neutron scattering instrument, operated by the Australian Centre for Neutron Scattering at the Australian Nuclear Science ...and Technology Organisation (ANSTO). BILBY provides a wide accessible q range (q ≃ 1.0 × 10−3 Å−1 to ∼1.8 Å−1) and variable wavelength resolution (Δλ/λ ≃ 3–30%) to complement the other small‐angle and ultra‐small‐angle neutron scattering capabilities available at ANSTO. Since its construction, BILBY has been used to study samples from a wide range of scientific disciplines, including biology, chemistry, physics and materials science. This article describes the BILBY design and components, and shows data collected from a number of reference samples.
A description is presented of the instrument design and performance of BILBY, the new time‐of‐flight small‐angle neutron scattering instrument located at the Australian Nuclear Science and Technology Organisation.
Rapid identification of the causative microorganism is important for appropriate antimicrobial therapy of bloodstream infections. Bacteria from positive blood culture (BC) bottles are not readily ...available for identification by matrix-assisted laser desorption ionization—time of flight mass spectrometry (MALDI-TOF MS). Lysis and centrifugation procedures suggested for direct MALDI-TOF MS from positive BCs without previous culture are associated with additional hands-on processing time and costs. Here, we describe an alternative approach applying MALDI-TOF MS from bacterial cultures incubated very briefly on solid medium. After plating of positive BC broth on Columbia blood agar (n = 165), MALDI-TOF MS was performed after 1.5, 2, 3, 4, 5, 6, 7, 8, 12 and (for control) 24 h of incubation until reliable identification to the species level was achieved (score ≥2.0). Mean incubation time needed to achieve species-level identification was 5.9 and 2.0 h for Gram-positive aerobic cocci (GPC, n = 86) and Gram-negative aerobic rods (GNR, n = 42), respectively. Short agar cultures with incubation times ≤2, ≤4, ≤6, ≤8 and ≤12 h yielded species identification in 1.2%, 18.6%, 64.0%, 96.5%, 98.8% of GPC, and in 76.2%, 95.2%, 97.6%, 97.6%, 97.6% of GNR, respectively. Control species identification at 24 h was achieved in 100% of GPC and 97.6% of GNR. Ethanol/formic acid protein extraction performed for an additional 34 GPC isolates cultivated from positive BCs showed further reduction in time to species identification (3.1 h). MALDI-TOF MS using biomass subsequent to very short-term incubation on solid medium allows very early and reliable bacterial identification from positive BCs without additional time and cost expenditure.
The CORELLI instrument at Oak Ridge National Laboratory is a statistical chopper spectrometer designed and optimized to probe complex disorder in crystalline materials through diffuse scattering ...experiments. On CORELLI, the high efficiency of white‐beam Laue diffraction combined with elastic discrimination have enabled an unprecedented data collection rate to obtain both the total and the elastic‐only scattering over a large volume of reciprocal space from a single measurement. To achieve this, CORELLI is equipped with a statistical chopper to modulate the incoming neutron beam quasi‐randomly, and then the cross‐correlation method is applied to reconstruct the elastic component from the scattering data. Details of the implementation of the cross‐correlation method on CORELLI are given and its performance is discussed.
With implementation of the cross‐correlation technique at the short‐pulse Spallation Neutron Source (SNS), Oak Ridge, Tennessee, USA, CORELLI obtains both the total scattering and the elastic‐only scattering simultaneously from a single measurement with an unprecedented data collection rate.
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