J. Marchal

Fast X-ray powder diffraction on I11 at Diamond.

The commissioning and performance characterization of a position-sensitive detector designed for fast X-ray powder diffraction experiments on beamline I11 at Diamond Light Source are described. The detecting elements comprise 18 detector-readout modules of MYTHEN-II silicon strip technology tiled to provide 90° coverage in 2θ. The modules are located in a rigid housing custom designed at Diamond with control of the device fully integrated into the beamline data acquisition environment. The detector is mounted on the I11 three-circle powder diffractometer to provide an intrinsic resolution of Δ2θ approximately equal to 0.004°. The results of commissioning and performance measurements using reference samples (Si and AgI) are presented, along with new results from scientific experiments selected to demonstrate the suitability of this facility for powder diffraction experiments where conventional angle scanning is too slow to capture rapid structural changes. The real-time dehydrogenation of MgH(2), a potential hydrogen storage compound, is investigated along with ultrafast high-throughput measurements to determine the crystallite quality of different samples of the metastable carbonate phase vaterite (CaCO(3)) precipitated and stabilized in the presence of amino acid molecules in a biomimetic synthesis process.

Detector Developments at DESY

With the increased brilliance of state-of-the-art synchrotron radiation sources and the advent of free-electron lasers (FELs) enabling revolutionary science with EUV to X-ray photons comes an urgent need for suitable photon imaging detectors. Requirements include high frame rates, very large dynamic range, single-photon sensitivity with low probability of false positives and (multi)-megapixels. At DESY, one ongoing development project - in collaboration with RAL/STFC, Elettra Sincrotrone Trieste, Diamond, and Pohang Accelerator Laboratory - is the CMOS-based soft X-ray imager PERCIVAL. PERCIVAL is a monolithic active-pixel sensor back-thinned to access its primary energy range of 250 eV to 1 keV with target efficiencies above 90%. According to preliminary specifications, the roughly 10 cm × 10 cm, 3.5k × 3.7k monolithic sensor will operate at frame rates up to 120 Hz (commensurate with most FELs) and use multiple gains within 27 µm pixels to measure 1 to ∼100000 (500 eV) simultaneously arriving photons. DESY is also leading the development of the AGIPD, a high-speed detector based on hybrid pixel technology intended for use at the European XFEL. This system is being developed in collaboration with PSI, University of Hamburg, and University of Bonn. The AGIPD allows single-pulse imaging at 4.5 MHz frame rate into a 352-frame buffer, with a dynamic range allowing single-photon detection and detection of more than 10000 photons at 12.4 keV in the same image. Modules of 65k pixels each are configured to make up (multi)megapixel cameras. This review describes the AGIPD and the PERCIVAL concepts and systems, including some recent results and a summary of their current status. It also gives a short overview over other FEL-relevant developments where the Photon Science Detector Group at DESY is involved.

PERCIVAL: The design and characterisation of a CMOS image sensor for direct detection of low-energy X-rays

Free-Electron Lasers and Synchrotrons are rapidly increasing in brilliance. This has led a requirement of large dynamic range and high frame rate sensors that is now being fulfilled by the PERCVIAL CMOS imager for direct X-ray detection developed at Rutherford Appleton Laboratory. Utilising a lateral overflow pixel and back-side illumination, PERCIVAL simultaneously achieves low-noise single-photon detection and high full well up to 107 e-, all while maintaining a frame rate of 120Hz. PERCIVAL is currently in test structure stage, and will be produced in 2 Mpixel and 13 Mpixel “waferscale” variants in 2015.

A compact and portable X-ray beam position monitor using Medipix3

The present work reports on the design and implementation of a novel portable X-ray beam diagnostics (XBPM) device. The device is transparent to the X-ray beam and provides real-time measurements of beam position, intensity, and size. The measurement principle is based on a pinhole camera which records scattered radiation from a Kapton foil which is placed in the beam path. The use of hybrid detectors (Medipix3) that feature a virtually noiseless readout system with capability of single photon detection and energy resolving power enables the diagnostics with a better resolution and higher sensitivity compared to the use of traditional indirect X-ray detection schemes. We describe the detailed system design, which consists of a vacuum compatible focal plane sensor array, a sensor conditioning and readout board and a heterogeneous data processing unit, which also acts as a network server that handles network communications with clients. The readout protocol for the Medipix3 sensor is implemented using field programmable gate array (FPGA) logic resulting in a versatile and scalable system that is capable of performing advanced functions such as data compression techniques and feature extraction. For the system performance measurements, we equipped the instrument with a single Medipix3 die, bump bonded to a Si sensor, rather than four for which it was designed. Without data compression, it is capable of acquiring magnified images and profiles of synchrotron X-ray beams at a transfer rate through Ethernet of 27 frames/s for one Medipix3 die.

Performance of the Lancelot Beam Position Monitor at the Diamond Light Source

The Lancelot beam position and profile monitor records the scattered radiation off a thin, low-density foil, which passes through a pinhole perpendicular to the path of the beam and is detected by a Medipix3RX sensor. This arrangement does not expose the detector to the direct beam at synchrotrons and results in a negligible drop in flux downstream of the module. It allows for magnified images of the beam to be acquired in real time with high signal-to-noise ratios, enabling measurements of tiny displacements in the position of the centroid of approximately 1 μm. It also provides a means for independently measuring the photon energy of the incident monoenergetic photon beam. A constant frame rate of up to 245 Hz is achieved. The results of measurements with two Lancelot detectors installed in different environments at the Diamond Light Source are presented and their performance is discussed.

Experimental characterization of the PERCIVAL soft X-ray detector

Considerable interest has been manifested for the use of high-brilliance X-ray synchrotron sources and X-ray Free-Electron Lasers for the investigation of samples.

In situ micro-focused X-ray beam characterization with a lensless camera using a hybrid pixel detector

Position and size measurements of a micro-focused X-ray beam, using an X-ray beam imaging device based on a lensless camera that collects radiation scattered from a thin foil placed in the path of the beam at an oblique angle, are reported.

PERCIVAL soft X-ray imager

Our goal is to provide the scientific community with a large (10cm × 10cm) pixellated detector featuring a large dynamic range (1-105 photons), good spatial resolution (27μm), good Quantum Efficiency (QE) in the low energy range (250eV-1keV), variable readout speed (up to 120 frames/s), i.e. with characteristics compatible with user needs at todays of low-energy Free Electron Lasers (FEL) and synchrotron sources.

Medipix3 array high performance read-out board for synchrotron research

The Medipix3 ASIC is one of the most advanced chip that is presently available to build photon counting area detectors. The capabilities of the chip include adjacent pixels charge summing circuitry to sort out the distortion due to charge sharing, simultaneous counting and read‐out that enables frames to be acquired without dead time, the colour mode of operation that enables up to eight energy bands to be acquired. In order to fully exploit the capabilities of the Medipix3 chip in synchrotron research, a high performance electronic board capable of driving large arrays of chips is necessary. We propose a parallel read‐out board of Medipix3 chip arrays with a scalable architecture that allows driving the Medipix3 chip in all of its modes of operation. The board functions include the control of the chip arrays, data formatting and data compression, the management of the communications with the data storage devices, and operation in various trigger modes. In addition to this the board will have some “intelligence” embedded. This will add some very important features to the final detector such as pattern recognition, capability of variable frame duration as a function of the photon flux, feedback to other equipment and real time calculations of data relevant to experiments such as the autocorrelation function.The Medipix3 ASIC is one of the most advanced chip that is presently available to build photon counting area detectors. The capabilities of the chip include adjacent pixels charge summing circuitry to sort out the distortion due to charge sharing, simultaneous counting and read‐out that enables frames to be acquired without dead time, the colour mode of operation that enables up to eight energy bands to be acquired. In order to fully exploit the capabilities of the Medipix3 chip in synchrotron research, a high performance electronic board capable of driving large arrays of chips is necessary. We propose a parallel read‐out board of Medipix3 chip arrays with a scalable architecture that allows driving the Medipix3 chip in all of its modes of operation. The board functions include the control of the chip arrays, data formatting and data compression, the management of the communications with the data storage devices, and operation in various trigger modes. In addition to this the board will have some “intell...