Originally conceived and developed at the European Synchrotron Radiation Facility (ESRF) as an "area" detector for rapid x-ray imaging studies, the fast readout low noise (FReLoN) detector of the ESRF [J.-C. Labiche, ESRF Newsletter 25, 41 (1996)] has been demonstrated to be a highly versatile and unique detector. Charge coupled device (CCD) cameras at present available on the public market offer either a high dynamic range or a high readout speed. A compromise between signal dynamic range and readout speed is always sought. The parameters of the commercial cameras can sometimes be tuned, in order to better fulfill the needs of specific experiments, but in general these cameras have a poor duty cycle (i.e., the signal integration time is much smaller than the readout time). In order to address scientific problems such as time resolved experiments at the ESRF, a FReLoN camera has been developed by the Instrument Support Group at ESRF. This camera is a low noise CCD camera that combines high dynamic range, high readout speed, accuracy, and improved duty cycle in a single image. In this paper, we show its application in a quasi-one-dimensional sense to dynamic problems in materials science, catalysis, and chemistry that require data acquisition on a time scale of milliseconds or a few tens of milliseconds. It is demonstrated that in this mode the FReLoN can be applied equally to the investigation of rapid changes in long range order (via diffraction) and local order (via energy dispersive extended x-ray absorption fine structure) and in situations of x-ray hardness and flux beyond the capacity of other detectors.

A 2D photon-counting X-ray detector system with 1.4 kHz frame rate and 55 µm spatial resolution has been developed and commissionned on ESRF beamlines. The system called MAXIPIX (Multichip Area X-ray detector based on a photon-counting PIXel array) consists of a detector module implementing up to five MEDIPIX-2 or TIMEPIX photon-counting readout chips, a custom readout interface board and a Linux acquisition workstation. The detector module readout time is 290 microseconds, allowing the system to achieve sustained frame rates of 280 Hz to 1400 Hz depending on the number of connected chips. An effective time resolution of 60 ns was measured using the ESRF pulsed modes and a TIMEPIX module. The system architecture and characteristics are presented, as well as a summary of its applications on ESRF beamlines.

Theoretically core-multishell nanowires under a cross-section of hexagonal geometry should exhibit peculiar confinement effects. Using a hard X-ray nanobeam, here we show experimental evidence for carrier localization phenomena at the hexagon corners by combining synchrotron excited optical luminescence with simultaneous X-ray fluorescence spectroscopy. Applied to single coaxial n-GaN/InGaN multiquantum-well/p-GaN nanowires, our 1 experiment narrows the gap between optical microscopy and high-resolution X-ray imaging, and calls for further studies on the underlying mechanisms of optoelectronic nanodevices.KEYWORDS: core-multishell nanowires, carrier confinement, X-ray nanoprobe, light-emitting diodes, nanodevicesThe controlled growth of core-multishell nanowires allows fundamental investigations of quantum confinement phenomena. 1 So far, sophisticated coaxial band structure engineering has already been used to produce size-dependent effects for advanced light-emitting diodes. 2 Although theory suggests that the carrier distributions exhibit two dimensional confinement in nanowires under a cross-section of hexagonal geometry, 3 its direct observation has never been addressed. Owing to the central role of quantum confinement in limiting carrier dynamics, X-ray excited optical luminescence 4 is accordingly very attractive for imaging single core-multishell nanowires. With the advent of X-ray focusing optics, 5 it has become a challenge to extend the technique into the nanoscale and hard X-ray regime. The emergence of imaging schemes capable of overcoming Abbe's diffraction barrier ( /2NA, where is the wavelength of light and NA is λ λ the numerical aperture of the lens) is crucial for optical microscopy. 6 For example, using parallel-detection mode cathodoluminescence-scanning transmission electron microscopy, Lim dispersive Si drift detector, while the luminescence is detected by a far-field optical system. The collected photons are focused on an optical fibre, which transmits the light to a spectrometer equipped with a linear charge coupled device detector. Besides the depth resolution, which is determined by the incident X-ray photons, the spatial resolution of our approach is governed by the spot size of the incident X-ray beam and the diffusion length of carriers. 11 For a quantum emitter, like a single nanowire or quantum dot, the resolution can be enhanced several times 3 compared with standard optical excitation. In combination with the high brightness of the thirdgeneration synchrotron source, our current diffraction limited X-ray lenses 12 allow for nanoscale lateral and spectral analysis with short acquisition times (typically from 200 ms to 1 s per spectrum).As a proof of concept, we apply this technique to single coaxial p-GaN/InGaN multi-quantumwell/n-GaN/ZnO nanowires grown by metal-organic vapour phase epitaxy. 13 Recent calculations indicate that the modulation of the radial elemental composition within nanoscale hexagonal geometry introduces new complexities that create novel confinemen...

The performance of the high-resolution fast-photon-counting Eiger 500k detector for sub-millisecond X-ray photon correlation spectroscopy measurement is demonstrated.

The ID22 beamline is dedicated to hard X-ray microanalysis allowing the combination of fluorescence, spectroscopy, diffraction and tomography techniques in a wide energy range from 6 to 70 keV. The recent installation of an in-vacuum undulator, a new sample stage and the adaptation of various focusing optics has contributed to a great improvement in the capabilities of the beamline, which is now accessed by a wide user community issued from medical, earth and environmental science, archaeology and material science. Many applications requiring low detection limits for localization/speciation of trace elements together with structural analysis have been developed at the beamline on the (sub)micrometer scale. The possibility of combining simultaneously different analytical probes offers the opportunity of a thorough study of a given sample or scientific problem. This paper presents a review of the recent developments of the beamline and a detailed description of its capabilities through examples from different fields of applications.