Fast GPU-based spot extraction for energy-dispersive X-ray Laue diffraction

Abstract

This paper describes a novel method for fast online analysis of X-ray Laue spots taken by means of an energy-dispersive X-ray 2D detector. Current pnCCD detectors typically operate at some 100 Hz (up to a maximum of 400 Hz) and have a resolution of 384 × 384 pixels, future devices head for even higher pixel counts and frame rates.The proposed online data analysis is based on a computer utilizing multiple Graphics Processing Units (GPUs), which allow for fast and parallel data processing. Our multi-GPU based algorithm is compliant with the rules of stream-based data processing, for which GPUs are optimized. The paper's main contribution is therefore an alternative algorithm for the determination of spot positions and energies over the full sequence of pnCCD data frames. Furthermore, an improved background suppression algorithm is presented.The resulting system is able to process data at the maximum acquisition rate of 400 Hz. We present a detailed analysis of the spot positions and energies deduced from a prior (single-core) CPU-based and the novel GPU-based data processing, showing that the parallel computed results using the GPU implementation are at least of the same quality as prior CPU-based results. Furthermore, the GPU-based algorithm is able to speed up the data processing by a factor of 7 (in comparison to single-core CPU-based algorithm) which effectively makes the detector system more suitable for online data processing.

Application of a pnCCD for energy-dispersive Laue diffraction with ultra-hard X-rays

“…The background of air-scattered photons superimposed on the diffraction signals of the sample is relatively homogeneous across the image, whereas in the direct vicinity of the beam stop a larger background level was measured. Ninety-two Laue spots of GaAs could be identified by applying the sequential CPU-based algorithm for spot localization described by Alghabi et al (2014). Despite the beam cross section of 100 Â 100 mm the collected Bragg peaks covered areas with a minimum size of 5 Â 5 pixels in the plane of detection.…”

“…Recently, the spatial and energetic profiles of individual Bragg peaks generated by a deformed Cu crystal were resolved to identify dislocations inside the sample (Abboud et al, 2014). In future applications, energy-dispersive Laue diffraction will be supported by GPUbased software tools for fast online data analysis in near real time (Alghabi et al, 2014).…”

Fast GPU-based absolute intensity determination for energy-dispersive X-ray Laue diffraction

“…Areas such as medical physics [7,8], high-energy physics [9][10][11] and lattice quantum chromodynamics [12,13] have also witnessed increasing use of GPUs for acceleration of scientific computing. Recently, a GPU data processing scheme was successfully applied to accelerate the extraction of the Laue spots' positions and energies from a pnCCD data set for energy-dispersive Laue diffraction of hen egg-white lysozyme, resulting in a 7 times faster processing time [14][15][16].…”

“…Following the discussion above, we have applied the procedure described in section 3 to a number of spots and analysed the results using the fitting error. The spots we have used in this experiment are those computed by the GPU algorithm in [14] from a raw data set of 100000 pnCCD frames (N = 100000) generated during an energy-dispersive X-ray Laue diffraction experiment. The experiment is carried out at room temperature with no cooling and the pnCCD image plane is perpendicular to the incident beam.…”

“…Since the procedure relies on the knowledge of Miller indices (see section 3.3) we have used only a subset of those spots which are correctly indexed with adequate accuracy during unit cell calculation and spot indexation (see figure 1). The subset we have chosen comprises 284 spots which were indexed by a tolerance of 20% (see table 2 in [14]). Also, the parameters E min , E max , E max_bg and δ in section 3 are set to 8.5 keV, 81.9 keV, 30 keV and 2 for all the spots, respectively.…”