Fast Detector System Research Articles

Room-temperature macromolecular serial crystallography using synchrotron radiation.

A new approach for collecting data from many hundreds of thousands of microcrystals using X-ray pulses from a free-electron laser has recently been developed. Referred to as serial crystallography, diffraction patterns are recorded at a constant rate as a suspension of protein crystals flows across the path of an X-ray beam. Events that by chance contain single-crystal diffraction patterns are retained, then indexed and merged to form a three-dimensional set of reflection intensities for structure determination. This approach relies upon several innovations: an intense X-ray beam; a fast detector system; a means to rapidly flow a suspension of crystals across the X-ray beam; and the computational infrastructure to process the large volume of data. Originally conceived for radiation-damage-free measurements with ultrafast X-ray pulses, the same methods can be employed with synchrotron radiation. As in powder diffraction, the averaging of thousands of observations per Bragg peak may improve the ratio of signal to noise of low-dose exposures. Here, it is shown that this paradigm can be implemented for room-temperature data collection using synchrotron radiation and exposure times of less than 3 ms. Using lysozyme microcrystals as a model system, over 40 000 single-crystal diffraction patterns were obtained and merged to produce a structural model that could be refined to 2.1 Å resolution. The resulting electron density is in excellent agreement with that obtained using standard X-ray data collection techniques. With further improvements the method is well suited for even shorter exposures at future and upgraded synchrotron radiation facilities that may deliver beams with 1000 times higher brightness than they currently produce.

A high-throughput x-ray microtomography system at the Advanced Photon Source

A third-generation synchrotron radiation source provides enough brilliance to acquire complete tomographic data sets at 100 nm or better resolution in a few minutes. To take advantage of such high-brilliance sources at the Advanced Photon Source, we have constructed a pipelined data acquisition and reconstruction system that combines a fast detector system, high-speed data networks, and massively parallel computers to rapidly acquire the projection data and perform the reconstruction and rendering calculations. With the current setup, a data set can be obtained and reconstructed in tens of minutes. A specialized visualization computer makes rendered three-dimensional (3D) images available to the beamline users minutes after the data acquisition is completed. This system is capable of examining a large number of samples at sub-μm 3D resolution or studying the full 3D structure of a dynamically evolving sample on a 10 min temporal scale. In the near future, we expect to increase the spatial resolution to below 100 nm by using zone-plate x-ray focusing optics and to improve the time resolution by the use of a broadband x-ray monochromator and a faster detector system.

Time-resolved X-ray scattering using a high-intensity multilayer monochromator

A wide-bandpass monochromator and fast detector system at the new IBM/MIT beamline X-20C at the National Synchrotron Light Source allow the collection of X-ray scattering patterns within milliseconds. The monochromator incorporates artificial multilayers rather than crystals, and provides a flux of 1 × 10 13 photons/s at 6 keV with an energy resolution of ΔE E = 1.1 × 10 −2 fwhm. The detector system is based on a linear photodiode array. Using this beamline, we have carried out in situ time-resolved X-ray scattering studies of the initial kinetics of crystallization, phase separation, and ordering at time scales orders of magnitude faster than previously possible for such nonrepetitive processes.

A fast detector system with cooled NaI-scintillators

Detector systems with cooled non-thallium-activated NaI-crystals allow to improve the time resolution in γγ-coincidence experiments. Such a system has been developed and yielded typical time resolutions a factor of 2.5 better than conventional NaI(Tl)-systems. Two examples for possible applications are given.

High definition radiography of cast turbine blades as a method of detecting and evaluating the incidence of microporosity

An X-radiographic method is described which employs an image enlargement technique to measure microporosity. Using an extremely small focal spot, the Harwell E12 High Definition X-ray Unit is able to detect individual pores as small as 0.03 mm. A testing speed of 1000 blades per week is achieved using a fast detector system instead of conventional fine grained X-ray film.