CCD X-ray detectors

The most recent generation of CCD X-ray detectors enable laboratory structure determination on crystals of dimensions of 100 pm and in favorable cases smaller still. The use of synchrotron radiation may permit crystals of a few tens of microns in size to be studied. Typical intensity data collection time is usually of the order of a few hours (shorter for high flux synchrotron sources), but, with some compromise in precision, structure determination can be accomplished in some instances using data collection of less than an hour. 

Several other principles have been used to build X-ray detectors. For instance, ID detectors have been realized by diode arrays. 2D detectors have been realized by conversion of X-rays to visible light, photon amplification, and a television camera (VIDICON). CCD detectors have outperformed both diode arrays and the VIDI-CON. 

Pokric, M., et al. (2002). Large area high-resolution CCD-based X-ray detector for macromolecular crystallography. Nucl. Instrum. Meth. A. 477,166-171. 

The simplest X-ray detector, and for years the workhorse of detectors, is X-ray-sensitive film, but film has been almost completely replaced by image plates and CCD detectors, which are described in more detail later. Various types of cameras (next section) can direct reflections to detectors in useful arrangements, allowing precise determination of indices and intensities for thousands of reflections from a single image. 

Tate, M. W., Eikenberry, E. F., Barna, S. L., Wall, M. E., Lowrance, J. L., and Gruner, S. M. (1995). A large-format high-resolution area X-ray-detector based on a fiberoptically bonded charge-coupled-device (CCD). /. Appl. Crystallogr. 28, 196—205. 

The CCDs for the direct measurement of the antiprotonic X-rays were installed in the second bore hole of the cyclotron trap close to the stop volume. Thus, a few per mille of the full solid angle were covered. The relative efficiency and the in-beam resolution function were obtained in a separate measurement from the saturated X-ray transitions in pN. Two different types of CCDs were used (i) MOS CCDs with a typical depletion depth of about 30 pm [22,23] and (ii) the prototype of a high-rate X-ray detector based on a fully depleted (290 pm) pn-CCD [24],... 

Fig. 2. Set-up of cyclotron trap, crystal spectrometer, and CCD detectors in LEAR, experiment PS207. For the pH measurement, the two-arm crystal spectrometer was equipped in total with 3 spherically-bent quartz crystals each reflecting to a separate X-ray detector. Further CCD detectors installed in the second bore hole of the cyclotron trap were used for direct measurements of antiprotonic X-rays...

Alongside improvements in synchrotron sources, X-ray detectors have improved enormously. Up to the early 1990s X-ray film was the detector of choice at synchrotrons because of its high spatial resolution, despite its poor efficiency and low dynamic range. Imaging plate and charge coupled device (CCD) detectors swept film aside in the early-to-mid 1990s. 

CCD s have found some limited applications as X-ray detectors... 

Luminometers are instruments used to measure chemiluminescence and electrochemUuminescence. The basic components are (1) the sample cell housed in a light-tight chamber, (2) the mjection system to add reagents to the sample cell, and (3) the detector. The detector is usually a photomultiplier tube. However, a CCD, x-ray film, or pho-... 

Currently under development are the next generation x-ray detectors such as the pixel-array, amorphous silicon, and solid state detectors. These detectors offer a larger active area, lower background, faster readout, and higher dynamic range than the current CCD or IP systems. 

The CCD is a semi-conductor detector. It can be used as an X-ray detector (for reviews see Allinson (1982), Milch et al (1982) and Allin-son (1989)) either by direct illumination of the X-rays onto the silicon or by conversion of the X-rays in a phosphor to visible light which is then incident onto the silicon. The previous section dealt with phosphor coupled systems based on television cameras. The CCD can replace the television camera. This is the basis of the system being developed by Strauss et al (1987) and Westbrook (1988) see figure 5.25. An alternative is to use direct illumination onto a so-called deep depletion CCD. CCD... 

The position-sensitive detector registers the diffraction pattern of the sample by moving around the sample. The detector is usually a scintillation counter or more recently an array of X-ray detectors (CCD), which allows more data to be collected simultaneously. 

J.D. Cox, D.S. Langford, D.W. Williams Electronic intraoral dental imaging system employing a direct sensing CCD array. In X-ray Detector Physics and Applications II, ed. by V.J. Orphan, SPIE 2009 (1993)... 

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