81 research outputs found
Integrated quantitative PIXE analysis and EDX spectroscopy using a laser-driven particle source
Among the existing elemental characterization techniques, Particle Induced
X-ray Emission (PIXE) and Energy Dispersive X-ray (EDX) spectroscopy are two of
the most widely used in different scientific and technological fields. Here we
present the first quantitative laser-driven PIXE and laser-driven EDX
experimental investigation performed at the Centro de L\'aseres Pulsados in
Salamanca. Thanks to their potential for compactness and portability,
laser-driven particle sources are very appealing for materials science
applications, especially for materials analysis techniques. We demonstrate the
possibility to exploit the X-ray signal produced by the co-irradiation with
both electrons and protons to identify the elements in the sample. We show
that, using the proton beam only, we can successfully obtain quantitative
information about the sample structure through laser-driven PIXE analysis.
These results pave the way towards the development of a compact and
multi-functional apparatus for the elemental analysis of materials based on a
laser-driven particle source.Comment: This project has received funding from the European Research Council
(ERC) under the European Union's Horizon 2020 research and innovation
programme (ENSURE grant agreement No. 647554). Submitted to Science Advances
on 20th May 2
Proton stopping measurements at low velocity in warm dense carbon
: Ion stopping in warm dense matter is a process of fundamental importance for the understanding of the properties of dense plasmas, the realization and the interpretation of experiments involving ion-beam-heated warm dense matter samples, and for inertial confinement fusion research. The theoretical description of the ion stopping power in warm dense matter is difficult notably due to electron coupling and degeneracy, and measurements are still largely missing. In particular, the low-velocity stopping range, that features the largest modelling uncertainties, remains virtually unexplored. Here, we report proton energy-loss measurements in warm dense plasma at unprecedented low projectile velocities. Our energy-loss data, combined with a precise target characterization based on plasma-emission measurements using two independent spectroscopy diagnostics, demonstrate a significant deviation of the stopping power from classical models in this regime. In particular, we show that our results are in closest agreement with recent first-principles simulations based on time-dependent density functional theory
Organizing risk: organization and management theory for the risk society
Risk has become a crucial part of organizing, affecting a wide range of organizations in all sectors. We identify, review and integrate diverse literatures relevant to organizing risk, building on an existing framework that describes how risk is organized in three ‘modes’ – prospectively, in real-time, and retrospectively. We then identify three critical issues in the existing literature: its fragmented nature; its neglect of the tensions associated with each of the modes; and its tendency to assume that the meaning of an object in relation to risk is singular and stable. We provide a series of new insights with regard to each of these issues. First, we develop the concept of a risk cycle that shows how organizations engage with all three modes and transition between them over time. Second, we explain why the tensions have been largely ignored and show how studies using a risk work perspective can provide further insights into them. Third, we develop the concept of risk translation to highlight the ways in the meanings of risks can be transformed and to identify the political consequences of such translations. We conclude the paper with a research agenda to elaborate these insights and ideas further
Finance as ‘bizarre bazaar’: using documents as a source of ethnographic knowledge
Markets and finance have long attracted ethnographic interest but the nature of their activity
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opaque,
secretive, and increasingly placeless
–
precludes traditional ethnographic fieldwork. In this paper we
propose documents as an
alternative access point to these organisations as an ethnographic object of
enquiry. Documents do not only present a written record, they also enact relationships and encode
tacit understandings. We develop Geertz’s work on the bazaar by taking an indire
ct route to access
the field site
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Collateral Debt Obligations
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through documents. In reading these documents, we
assume the position of investors who, in the absence of alternative publicly available information, are
dependent on the documentary accounts
made available to them by the sellers. These media act in
ways that are similar to tourist guidebooks, a comparison we use to reframe the exchange as one that
builds upon sociocultural relations rather than the abstract market relationships described by
m
ainstream economists. We propose that these documents are not merely representational artefacts
of the organisation, but serve to establish and maintain social relationships between buyers and
sellers through the management, standardisation and ritualisati
on of information disclosed to the
investor
Microanalysis of carbon isotope composition in organic matter by secondary ion mass spectrometry.
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