Large-area detector

Figure 21 Artist s depiction of a system for imaging scattered X-rays. A fixed collimator slit and a rotating collimator slit produce a scanning pencil beam. A transmission detector monitors the transmitted beam, whereas large-area detectors respond to forward-scattered and backscattered X-rays emanating from the bag.

Currently, there exist several other long-duration balloon detectors that will address this question with new observational results, including ATIC [23] and CREAM [24], However, it is clear that the full potential of direct measurements must be exploited with a large-area detector in space flight of several years duration. 

A good value for a large-area detector in a cosmic-ray experiment, which measures hadrons with energies up to beyond 10 TeY. 

A more detailed comparison of the ADXD and EDXD techniques must take into account many different parameters. The EDXD technique using conventional 2 kW X-ray tubes and a conical slit system permits, for instance, kinetic studies with time resolutions of a few minutes on simple samples under pressure, whereas the ADXD technique is several orders of magnitude slower even with a position-sensitive detector. On the other hand, the resolution of possible overlapping lines, especially with the large-area detector used with the conical slit system, is much poorer in the EDXD than in the ADXD technique. 

Figure 15 suggests that SPR sensors with large area detectors such as PDA or 2D array CCD can potentially achieve a better resolution compared to systems using linear CCD detectors. This comparison is related to the fact that more light is measured with large area detectors in the same period of time, which results in the reduction of the shot noise. 

Nondescanned detection splits off the fluorescence tight directly behind the microscope lens and directs it to a large-area detector. Consequently, acceptable light collection efficiency is obtained even for deep layers of highly scattering samples. Two-photon imaging with nondescanned detection can be used to image tissue layers several 100 pm (in extreme cases 1 mm) deep [85, 278, 344, 462, 534]. 

An additional push can be expected from new technical developments in TCSPC itself. The largest potential is probably in the development of new detectors. The introduction of direct (wide-field) imaging techniques is clearly hampered by the limited availability of position-sensitive detectors. In addition the selection of multianode PMTs is still very limited, especially for NIR-sensitive versions. Large-area detectors with 64 or more channels may result in considerable improvements in DOT techniques. Single photon APDs with improved timing stability are urgently required for single-molecule spectroscopy and time-resolved microscopy. 

The central source is efficient for large-area detectors such as NaI(Tl) detectors, where extremely high activity is not required. The source and its shield shadow the central area of the detector, slightly reducing its detection efficiency. The side source geometry is effective for medium- to large-area detectors when the source area is comparable to the detector area. 

A second major advantage of photoemissive devices is the ease with which uniform, large-area detector surfaces can be fabricated. Such surfaces, while important for simple photomultipliers, are a prerequisite for successful imaging devices, including both direct-view intensifiers and image tubes with scanned electron beam readout [5.3]. 

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