Development and application of photosensitive device systems to studies of biological and organic materials Page: 5 of 27
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Instruments GEN-V controller. This detector performs beautifully and is highly suitable
for a wide variety of diffraction problems in which the input aperture is limited to about 70
mm on the diagonal. The detector will be fully described in a manuscript in preparation.
It is now being routinely used for biomembrane research. This detector is highly suitable
for storage ring applications in which the detector readout time of about 4 seconds is not
limiting, ie, a large fraction of the static diffraction problems encountered. The detector
is not count-rate limited even at the highest available count-rates.
C) Ancillary X-ray Detector Components
Reference: Deckman et al, 1990; manuscripts in preparation; Eikenberry et al, 1991.
Many problems involving intensifiers, fiber-optic components, phosphors, CCDs, and
electronic CCD controllers were investigated over the course of assembling and evaluating
the four CCD detectors described in sections A & B, above; these are discussed in detail
in the papers describing the respective detectors. A few points are worth noting here:
(1) Several phosphor deposition procedures were developed which have improved efficiency
without substantially compromising the detector resolution. The trade-offs between the
use of different phosphors and different deposition procedures were examined in the context
of different experimental needs. (2) Fiber-optic taper technology appears to be such that
very high quality tapers up to 75 mm diameter are available. Beyond that, the vendor
base and the quality of the tapers both become severely limiting.(3) Image intensifiers
and air-path optics are to be avoided, if possible, because of inevitable electron and light
scatter problems, which compromise the ultimate contrast attainable. Image tubes are also
suffering from a decreasing vendor base. (4) High quality CCD control electronics appear
to be an art. Although many different controllers are available, few meet the Btringent noise
limitations required to fully utilize the capabilities of modern CCDs. (5) Trapless CCDs
have only recently become available. This is important because directly coupled fiber-optic
based detectors do not have airpaths suitable for the introduction of the “fat-zero” light
biasing which has traditionally been used to fill traps prior to exposure.
D) Detector Comparisons
Reference: Eikenberry et al, 1992.
A comparative study was performed on the capabilities of CCD detectors, x-ray stor-
age phosphors and x-ray film. The study, performed at Princeton and at CHESS demon-
strate that storage phosphors lack the sensitivity of CCD detectors and have serious sys-
tematic problems (probably mostly due to light scattering in the optical paths of the image
plate reader and in the plates) which compromise low contrast signal detection. In fact, at
very low contrasts (e.g. 5-10%), film is a superior detector to storage phosphors. At higher
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Gruner, S.M. & Reynolds, G.T. Development and application of photosensitive device systems to studies of biological and organic materials, report, May 15, 1992; United States. (https://digital.library.unt.edu/ark:/67531/metadc1072386/m1/5/: accessed May 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.