Neutron data acquisition

R., Williams, G. J. B., NEXDAS. Neutron and X-ray Data Acquisition System, unpublished work (1976). 

Three-dimensional H20 (liquid) Relatively high resolution technique ( - -T00-150 xm), applicable to typical fuel cell designs Need a powerful neutron source, extremely long data acquisition time (up to hours) limits data to steady-state... 

It is also interesting to note that the limitations of most neutron systems lie not in the neutron source(s) but rather in the (gamma ray) detectors and subsequent data acquisition system. The obvious need is for development of detectors with higher rate capability and improved energy resolution. All modern digital data processing techniques have allowed significant improvement in the performance of conventional scintillation detectors with respect to rate and pileup rejection. 

P.K. Van Staagen, T.G. Miller, B.C. Gibson and R.A. Krauss, High speed data acquisition for contraband identification using neutron transmission, AIP Conf. Proc., 392(pt. 2) (1997) 853-856. 

As will become apparent in the later chapters, the statistical nature of the conclusions is such that the present amount of data in the crystallographic data base is inadequate. We find ourselves presenting results that show well-defined trends, but in doing so, have come to realize that we need a tenfold increase in the information from X-ray and neutron crystallography before the conclusions drawn can become really definitive. This tenfold increase in structural data will surely come within the next decade, and will be useful only if the publication, data storage, and retrieval mechanisms keep pace with the accelerating rate of data acquisition. 

Kossiakoff (1985) pointed out that the most useful attribute of neutron diffraction studies of proteins (compared with X-ray diffraction) is their ability to locate hydrogen (or deuterium) experimentally. Recent advances in apparatus and data acquisition mean that this method will become increasingly valuable in the study of a-lactalbumin and lysozyme, especially in the location of water molecules and the dynamics of these proteins. An example of a recent application is that by Lehmann et al. (1985). 

In addition to the human labor problems created by chemical separation and ultra-clean environments, both neutron activation and thermal Ionization mass spectrometry require unique equipment that Is not available to most research groups. Because of these factors progress In trace metal analysis has been slow and practical data acquisition from large populations Is essentially non-existent ... 

Four main aspects are addressed in turn (i) neutron sources and reflectometer operation (ii) choice of substrate, substrate preparation, and characterization (iii) cell design and assembly and (iv) data acquisition and analysis. 

Other recently developed methods have also become available for adsorption studies. The availability of synchrotrons as excellent x-ray sources allows x-ray studies at liquid interfaces (Mohwald et al. 1990, Meunier Lee 1991, Daillant et al. 1991). The same applies for small angle neutron scattering (SANS, based on the different scattering cross section of hydrogen and deuterium). The use of SANS for dynamic studies of structures in membranes and at interfaces has been shown by different authors (Grundy et al. 1988, Bayerl et al. 1990, Vaknin et al. 1991). The method is characterised by a fast data acquisition and should allow dynamic investigations at freshly formed surfaces, as discussed by several authors (Blake, Howe, Penfold, private communication). 

Although not all of the experiments needed to determine residual stresses have been completed, some useful data has been gathered. As temperature increased, the diffraction peaks shifted to lower two theta values, indicating an increase in d-spacing correlating to thermal expansion of the composite material.(Figure 5) Once analysis of the powder samples is complete, the inherent thermal expansion of each phase can be calculated, which will allow the strains to be determined for each phase in the composite material. The diffraction patterns from the experiments also provided evidence that the use of B to produce the parts made neutron diffraction possible. The patterns were visible within the first few minutes of data acquisition, which indicated the excellent scattering from the material. 

The applications of neutron diffraction in coordination chemistry may be divided into two categories, single crystal and polycrystalline studies. This distinction arises because of the very different methods required in each case for both the data acquisition and its subsequent analysis. 

As NRA has grown from accelerator-based nuclear physics and expanded after the invention of solid-state detectors (the surface barrier Si detector for the detection of particles and Ge(Li) detectors for the detection of y rays), its instrumentation is very much similar to those used in particle and y-ray nuclear spectroscopy. The PIXE method also started to use an existing instrumentation, the Si(Li) X-ray detectors, nearly a decade later. Consequently, this review will refer to the previous O Sects. 33.1 and O 33.2 on PIXE and RBS concerning the acceleration and the formation of energetic ion beams, the internal and external sample chambers, scanning particle microprobe facilities, particle detection, and data acquisition. It will only deal with the characteristic features of the detection of ions and y rays produced in nuclear reactions. Neutrons are also produced in these reactions, but in practice they are rarely used for NRA. Because of space limitations, that technique (Bird and Williams 1989) will not be discussed. 

The acceptance criteria for the resolution of GSI I.D.5 (3) for internals vibration monitoring are provided in ANSI/ASME OM-5-1981, (Reference 2). This standard provides non-mandatory recommendations on the use of ex-core neutron detector signals for monitoring of core barrel axial preload loss. This standard also documents a program containing baseline, surveillance and diagnostic phases and provides recommendations for data acquisition frequency and analysis. 

For the low-k tests, the NTG was modified by (a) reducing the reference keff, (b) upgrading the data acquisition system, (c) changing the mode of component assay from incremental to continuous,..and (d) replacing the extended neutron source with a compact source. 

I.The first option consists of Tyree detectors (see option two below) integrated directly into a commercially available data acquisition system made by Eberline Corp. of Santa Fe, New Mexico. This option operates in a digital mode by detecting individual neutrons, transmitting pulses over a twisted shielded pair to the Eberiine data acquisition module (DAM), which then interfaces with the central control terminal ((2T-1). The CT-1 contains two microprocessors. The DAM and (2T-1 units cany out the data... 

A high resolution and high throughput gamma ray spectrometer with a Ge detector is required. A computer based multi-channel analyzer (MCA) with software to control data acquisition and to analyze spectra is also required. The detector assembly must be well shielded to minimize neutron activation of the detector itself and to reduce the background components. 

By means of neutron reflectivity [57] and neutron scattering [58] one can determine density profiles of adsorbed polymer layers, but the data acquisition time is usually of the order of hoius and therefore not very suitable for studying the dynamics of polymer layers. 

The objectives of various projects under the CRP varied from on-line monitoring and display of reactor status to detailed thermal hydraulic and neutronic analysis. The research work included the development of hardware and software for PC-controlled data acquisition systems, and analysis and processing of reactor data. Although a wide range of subjects was covered, the CRP could not cover all the desired topics. 

NIST Cold Neutron Research Facility. NG3 and NG7 30-meter SANS Instruments Data Acquisition Manual, January 1999. 

The demonstration that stars are capable of such nuclear fertihty is based upon a combination of knowledge from what appear to be widely separated areas of physics. One of these concerns the internal structure of stars, telling us the temperature and pressure at different depths. The other concerns the probabilities at different energies of all the possible reactions between various nuclei, and between those nuclei and protons or neutrons. In the latter case, the acquisition of the relevant data was greatly accelerated by the Second World War. The beauty of nuclear astrophysics rests upon the success of this marriage and the complementarity of the two disciplines it brings together. The nuclear butterfly has returned to its stellar chrysalis. 

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