About EPJ

The European Physical Journal (EPJ) is a series of peer-reviewed journals covering the whole spectrum of physics and related interdisciplinary subjects. EPJ is committed to high scientific quality in publishing and is indexed in all main citation databases.


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EPJ AP Highlight - Slowing dynamics of a supersonic beam

2D imaging of the slowed Ar* supersonic beam for a final velocity vF = 61 m/s. From this image, one can easily extract the beam divergence and the coherence radius with respect to the position and size of the effective source.

The present investigation of the slowing dynamics of a supersonic atom beam by a counter-propagating resonant laser light, in other words the dynamics of atoms in a so-called “Zeeman slower”, is characterized by two special features which are: (i) a close coupling between simulations and experiments using a nozzle beam of metastable argon atoms, (ii) the use in the simulations of a Monte-Carlo (MC) scheme aimed at analysing step by step (i.e. subsequent cycles of absorption-emission) the slowing process and describing in a realistic way atom random walks due to the spontaneous emission. It allows us to get calculated 2D images and radial profiles of the slowed beam, in good agreement with experiment. Other important characteristics as angular aperture, velocity spreads, coherence radius (not easy to be measured experimentally), etc. also result from the simulation. Since the 3D atomic motion within the laser field is considered, border effects can be studied, while they were not directly accessible in a simple radiative force model. It is finally shown that the experimental characteristics of the slowed beam are reproduced by the calculated ones, assuming a point- like source. In general a laser beam is an efficient tool to manipulate the atomic motion and its interaction with atoms can be accurately characterized by means of the present MC-code. Actually any configuration combining resonant light and atoms is relevant (provided that the semi-classical approximation is valid), in particular the use of a “pushing” laser to generate a slow atomic beam from a magneto-optical trap is a technique which has been successfully tested with metastable argon atoms. Here again the MC-code has been able to accurately predict the characteristics of the generated beam.


EPJ D Highlight - Bringing the chaos in light sources under control

Experimental reconstruction of the phase portrait of the quantum dot light emitting diode using the embedding technique.

Study investigates how best to stabilise the output of quantum dot LEDs

Noise is an issue in optical telecommunications. And findings means of controlling noise is key to physicists investigating light-emitting diodes or lasers. Now, an Italo-Iraqi team has worked on a particular type of light source, called the quantum dot light-emitting diode (QDLED). In a study published in EPJ D, Kais Al Namee from the National Institute of Optics, in Florence, Italy and colleagues, demonstrate that modulating bias current of the QDLED could lead to countering the noise. This, in turn, leads to stabilising such light sources, making them better suited for optical telecommunications.


EPJ Plus Focus Point - 3He replacement in neutron detection: Current status and perspectives

One of the most important issues that the neutron community is currently facing is related to the lack of 3He for detection purposes. This problem has triggered an interesting and stimulating research and development activity worldwide, with the aim of finding effective and cheap solutions for 3He replacement. With the advent of new materials, advanced electronics and more powerful real time computing tools it has now become possible to investigate novel designs of neutron detectors to be used in various fields of research and technology, and to address the needs of more sophisticated applications.

The aim of this issue is to present an up-to-date, although not exhaustive, review on the R&D activities on 3He-free neutron detectors, with the aim of generating further discussions and activities on the subject, stimulate synergies between groups with different expertise, and show examples of existing neutron sources where new detectors and techniques can be tested and validated. This EPJ Plus Focus Point addresses all aspects related to the design of an innovative 3He-free neutron detector, from the development of new detection concepts and active material, to fast front-end electronics and acquisition systems, to the availability of neutron beams of suitable energy for detector characterization.


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University of Twente, Netherlands
6-8 October 2015