Combined inversion of land and marine electrical resistivity tomography for submarine groundwater discharge and saltwater intrusion characterization

Electrical resistivity tomography (ERT) is particularly suited for the characterization of saltwater intrusion and submarine freshwater discharge, given its sensitivity to the electrical conductivity of pore water. A comprehensive survey might combine land ERT collected during low tide and marine ERT acquired with lower sensitivity due to the presence of a seawater layer, most often, inverted separately. In this contribution, we propose a new methodology to jointly invert land and marine ERT acquired along a same profile, bringing them to a common situation at high tide. We first estimate the electrical resistivity distribution under the land profile. Then, we compute a corrected data set for land ERT, simulating a data set collected with the same level of water as the marine ERT. Finally, both land and marine ERT data sets are inverted jointly. We show that the approach allows to better image the freshwater/saltwater distribution across the shoreline

NIR User Manual

Radiation detectors are used in nuclear security in an attempt to intercept illicit trafficking of radioactive or nuclear materials. In this field, several types of detectors are used to detect the presence of a source, to measure the exposure rate to men, to locate and to identify it. To test the performance of such detectors, many exposures with a radioactive source are required (typically 60), and the exposures need to be repeated with sources with different gamma-energies, and with neutron-emitting sources. For some tests, combinations of sources are used. IRMM and ITU jointly designed and built an instrument, named "NIR" that can expose a radioactive source for a defined amount of time. The instrument consists of a source holder, mounted on an electrically controlled cylinder. The cylinder pushes the source holder out of a radiation shield, and retracts the holder after the exposure time has elapsed. Unique about this instrument is the fact that it does not contain a fixed source. Instead, the user can choose any source available and mount it in the source holder. The motion of the source holder is very precisely controlled using a servo motor. It will always come to the same position, following the same motion profile. The instrument can be controlled from a distance using software running on a computer, thereby reducing exposure to operators, as compared to manually executed exposures. The instrument allows to test of several radiation detectors at the same time. The high speed of operation and precision results in a reduced total test time and an increased confidence in the test result. This document is the user manual of the instrument NIR, it contains the original instructions for transport, installation and operation.JRC.D.5-Nuclear physic

Determining the optimal focusing parameter in sparse promoting inversions of EMI surveys

If the magnetic field caused by a magnetic dipole is measured, the electrical conductivity of the subsurface can be determined by solving the inverse problem. For this problem a form of regularisation is required as the forward model is badly conditioned. Commonly, Tikhonov regularisation is used which adds the $\ell_2$-norm of the model parameters to the objective function. As a result, a smooth conductivity profile is preferred and these types of inversions are very stable. However, it can cause problems when the true profile has discontinuities causing oscillations in the obtained model parameters. To circumvent this problem, $\ell_0$-approximating norms can be used to allow discontinuous model parameters. Two of these norms are considered in this paper, the Minimum Gradient Support and the Cauchy norm. However, both norms contain a parameter which transforms the function from the $\ell_2$- to the $\ell_0$-norm. To find the optimal value of this parameter, a new method is suggested. It is based on the $L$-curve method and finds a good balance between a continuous and discontinuous profile. The method is tested on synthetic data and is able to produce a conductivity profile similar to the true profile. Furthermore, the strategy is applied to newly acquired real-life measurements and the obtained profiles are in agreement with the results of other surveys at the same location. Finally, despite the fact that the Cauchy norm is only occasionally used to the best of our knowledge, we find that it performs at least as good as the Minimum Gradient Support norm

Use of a CAEN digitiser for nuclear safeguards and security applications with a scintillator detector

The performance of a CAEN DT5751 digitiser for nuclear safeguards and security applications is discussed. The pulse shape processing firmware embedded in the digitiser was tested with a EJ-309 liquid scintillator, exposed to gamma and neutron radiation from radioactive sources and from a Van de Graaff and cyclotron-based accelerator. Software modules were developed for data acquisition and online analysis, and for more advanced off-line processing of data acquired in list mode. The potential use of a scintillator coupled to the digitiser for the detection of both gamma-rays and neutrons has been demonstrated.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Smart Search in Newspaper Archives Using Topic Maps

The OmniPaper project has implemented three information retrieval prototypes in the area of electronic news publishing. One prototype uses SOAP as communication protocol between the central system and a number of distributed news archives. The second prototype uses an RDF metadata database, enabling direct metadata queries to the central system. Finally the Topic Map prototype uses query expansion and semantic linking for smart metadata search. The Topic Map prototype enhances thesearch experience by implementing a knowledge layer that combines the semantic content of a lexical database, consisting of concepts and keywords, with a metadata-set of newspaper articles. The linking between both is currently implemented at the level of keywords but will be developed at the level of concepts in the final prototype. The knowledge layer has been designed from a Topic Map point of view, although the XTM syntax has not been used to avoid performance issues. The consortium’s adopted view on information publishing and retrieval considers querying and navigation as two very related actions that can both be captured under the name “search for relevant information”. Navigation forces the user to followpredefined paths whereas querying enables the user to look freely for a suitable starting point. The query and navigation functionality is provided through a web engine and is build on top of the information structure of the knowledge layer

List-mode data acquisition based on digital electronics - State-of-the-art report

This report deals with digital radiation detection systems employing list-mode data collection, which improves data analysis capabilities. Future data acquisition systems shall also ultimately enable the movement of detection data from first responders electronically to analysis centres rather than the costly and time consuming process of moving experts and/or samples. This new technology is especially useful in crisis events, when time and resources are sparse and increased analysis capacity is required. In order to utilise the opportunities opened by these new technologies, the systems have to be interoperable, so that the data from each type of detector can easily be analysed by different analysis centres. Successful interoperability of the systems requires that European and/or international standards are devised for the digitised data format. The basis of such a format is a list of registered events detailing an estimate of the energy of the detected radiation, along with an accurate time-stamp for recorded events (and optionally other parameters describing each event).JRC.G.5-Security technology assessmen