skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Optimal fine ϕ-slicing for single-photon-counting pixel detectors

Abstract

Fine ϕ-slicing substantially improves scaling statistics and anomalous signal for diffraction data collection with hybrid pixel detectors. The data-collection parameters used in a macromolecular diffraction experiment have a strong impact on data quality. A careful choice of parameters leads to better data and can make the difference between success and failure in phasing attempts, and will also result in a more accurate atomic model. The selection of parameters has to account for the application of the data in various phasing methods or high-resolution refinement. Furthermore, experimental factors such as crystal characteristics, available experiment time and the properties of the X-ray source and detector have to be considered. For many years, CCD detectors have been the prevalent type of detectors used in macromolecular crystallography. Recently, hybrid pixel X-ray detectors that operate in single-photon-counting mode have become available. These detectors have fundamentally different characteristics compared with CCD detectors and different data-collection strategies should be applied. Fine ϕ-slicing is a strategy that is particularly well suited to hybrid pixel detectors because of the fast readout time and the absence of readout noise. A large number of data sets were systematically collected from crystals of four different proteins in order to investigate the benefitmore » of fine ϕ-slicing on data quality with a noise-free detector. The results show that fine ϕ-slicing can substantially improve scaling statistics and anomalous signal provided that the rotation angle is comparable to half the crystal mosaicity.« less

Authors:
; ;  [1]
  1. Swiss Light Source at Paul Scherrer Institut, CH-5232 Villigen (Switzerland)
Publication Date:
OSTI Identifier:
22347905
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Crystallographica. Section D: Biological Crystallography; Journal Volume: 68; Journal Issue: Pt 1; Other Information: PMCID: PMC3245722; PMID: 22194332; PUBLISHER-ID: wd5161; OAI: oai:pubmedcentral.nih.gov:3245722; Copyright (c) Mueller et al. 2012; This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
Denmark
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ATOMS; CHARGE-COUPLED DEVICES; CRYSTALS; DIFFRACTION; HYBRIDIZATION; NOISE; PHOTONS; PROTEINS; RESOLUTION; ROTATION; SCALING; SIGNALS; X-RAY SOURCES

Citation Formats

Mueller, Marcus, E-mail: marcus.mueller@dectris.com, Wang, Meitian, and Schulze-Briese, Clemens. Optimal fine ϕ-slicing for single-photon-counting pixel detectors. Denmark: N. p., 2012. Web. doi:10.1107/S0907444911049833.
Mueller, Marcus, E-mail: marcus.mueller@dectris.com, Wang, Meitian, & Schulze-Briese, Clemens. Optimal fine ϕ-slicing for single-photon-counting pixel detectors. Denmark. doi:10.1107/S0907444911049833.
Mueller, Marcus, E-mail: marcus.mueller@dectris.com, Wang, Meitian, and Schulze-Briese, Clemens. 2012. "Optimal fine ϕ-slicing for single-photon-counting pixel detectors". Denmark. doi:10.1107/S0907444911049833.
@article{osti_22347905,
title = {Optimal fine ϕ-slicing for single-photon-counting pixel detectors},
author = {Mueller, Marcus, E-mail: marcus.mueller@dectris.com and Wang, Meitian and Schulze-Briese, Clemens},
abstractNote = {Fine ϕ-slicing substantially improves scaling statistics and anomalous signal for diffraction data collection with hybrid pixel detectors. The data-collection parameters used in a macromolecular diffraction experiment have a strong impact on data quality. A careful choice of parameters leads to better data and can make the difference between success and failure in phasing attempts, and will also result in a more accurate atomic model. The selection of parameters has to account for the application of the data in various phasing methods or high-resolution refinement. Furthermore, experimental factors such as crystal characteristics, available experiment time and the properties of the X-ray source and detector have to be considered. For many years, CCD detectors have been the prevalent type of detectors used in macromolecular crystallography. Recently, hybrid pixel X-ray detectors that operate in single-photon-counting mode have become available. These detectors have fundamentally different characteristics compared with CCD detectors and different data-collection strategies should be applied. Fine ϕ-slicing is a strategy that is particularly well suited to hybrid pixel detectors because of the fast readout time and the absence of readout noise. A large number of data sets were systematically collected from crystals of four different proteins in order to investigate the benefit of fine ϕ-slicing on data quality with a noise-free detector. The results show that fine ϕ-slicing can substantially improve scaling statistics and anomalous signal provided that the rotation angle is comparable to half the crystal mosaicity.},
doi = {10.1107/S0907444911049833},
journal = {Acta Crystallographica. Section D: Biological Crystallography},
number = Pt 1,
volume = 68,
place = {Denmark},
year = 2012,
month = 1
}
  • The authors report on the imaging capabilities of a mammographic system demonstrator based on GaAs pixel detectors operating in single photon counting (SPC) mode. The system imaging performances have been assessed by means of the transfer functions: The modulation transfer function (MTF), the normalized noise power spectrum, and the detective quantum efficiency (DQE) have been measured following the guidelines of the IEC 62220-1-2 protocol. The transfer function analysis has shown the high spatial resolution capabilities of the GaAs detectors. The MTF calculated at the Nyquist frequency (2.94 cycles/mm) is indeed 60%. The DQE, measured with a standard mammographic beam setupmore » (Mo/Mo, 28 kVp, with 4 mm Al added filter) and calculated at zero frequency, is 46%. Aiming to further improve the system's image quality, the authors investigate the DQE limiting factors and show that they are mainly related to system engineering. For example, the authors show that optimization of the image equalization procedure increases the DQE(0) up to 74%, which is better than the DQE(0) of most clinical mammographic systems. The authors show how the high detection efficiency of GaAs detectors and the noise discrimination associated with the SPC technology allow optimizing the image quality in mammography. In conclusion, the authors propose technological solutions to exploit to the utmost the potentiality of GaAs detectors coupled to SPC electronics.« less
  • Purpose: Detectors with hexagonal pixels require resampling to square pixels for distortion-free display of acquired images. In this work, the presampling modulation transfer function (MTF) of a hexagonal pixel array photon-counting CdTe detector for region-of-interest fluoroscopy was measured and the optimal square pixel size for resampling was determined. Methods: A 0.65mm thick CdTe Schottky sensor capable of concurrently acquiring up to 3 energy-windowed images was operated in a single energy-window mode to include ≥10 KeV photons. The detector had hexagonal pixels with apothem of 30 microns resulting in pixel spacing of 60 and 51.96 microns along the two orthogonal directions.more » Images of a tungsten edge test device acquired under IEC RQA5 conditions were double Hough transformed to identify the edge and numerically differentiated. The presampling MTF was determined from the finely sampled line spread function that accounted for the hexagonal sampling. The optimal square pixel size was determined in two ways; the square pixel size for which the aperture function evaluated at the Nyquist frequencies along the two orthogonal directions matched that from the hexagonal pixel aperture functions, and the square pixel size for which the mean absolute difference between the square and hexagonal aperture functions was minimized over all frequencies up to the Nyquist limit. Results: Evaluation of the aperture functions over the entire frequency range resulted in square pixel size of 53 microns with less than 2% difference from the hexagonal pixel. Evaluation of the aperture functions at Nyquist frequencies alone resulted in 54 microns square pixels. For the photon-counting CdTe detector and after resampling to 53 microns square pixels using quadratic interpolation, the presampling MTF at Nyquist frequency of 9.434 cycles/mm along the two directions were 0.501 and 0.507. Conclusion: Hexagonal pixel array photon-counting CdTe detector after resampling to square pixels provides high-resolution imaging suitable for fluoroscopy.« less
  • We demonstrate a scalable readout scheme for an infrared single-photon pulse-position camera consisting of WSi superconducting nanowire single-photon detectors. For an N × N array, only 2 × N wires are required to obtain the position of a detection event. As a proof-of-principle, we show results from a 2 × 2 array.
  • A single Photon Counting pixel detector readout Chip (PCC) has been derived from previous work in the CERN RD19 collaboration for particle physics tracking devices, recently developed for high energy physics experiments. The readout chip is a 64 x 64 matrix of identical 170 {micro}m x 170 {micro}m cells. It is to be bump-bonded to an equally segmented 1 cm{sup 2} matrix of semiconductor sensors, e.g. Si or GaAs. Each readout cell comprises a preamplifier, a discriminator and a 15-bit counter. The input noise is 170 e{sup {minus}} rms. At the lowest nominal threshold of 1,400 e{sup {minus}} (5.1 keVmore » in Si) the cells exhibit a threshold distribution with a spread before adjustment of 350 e{sup {minus}} rms. Each cell has a 5-bit register which allows masking, test-enable and 3-bit individual threshold adjust. After adjustment the threshold spread is reduced to 80 e{sup {minus}} rms. Absolute calibration of the electrically measured equivalent charge can be done once the readout chip is bump-bonded to a detector.« less
  • Medipix3 is a single photon-counting pixel readout chip whose new front-end architecture aims to eliminate the spectral distortion produced by charge diffusion in highly segmented semiconductor detectors. The chip requires area and power-efficient reconfigurable digital counters and shift registers that can be integrated with other photon-processing analog and digital circuits within the 55 {mu}mx55 {mu}m pixel area. This work proposes a configurable-depth, programmable mode digital counter for use in Medipix3.