Detector size

The results in Table 12 are considered very conservative by the North American Rockwell authors, since they were not obtained under optimum conditions. Such conditions must take into account the.type of luggage, conveyor belt speed, detector size, type of signal process-... 

Jackson, C., Computer simulation study of multi-detector size-exclusion chromatography of branched molecular mass distributions, /. Chromatogr. A, 662,... 

Jackson, C. and Barth, H. G., Concerns regarding the practice of multiple detector size-exclusion chromatography, in Chromatographic Characterization of Polymers, Hyphenated and Multidimensional Techniques, Provder, T., Barth, H. G., and Urban, M. W., Eds., American Chemical Society, Washington, D.C., 1995. chap. 5. 

The pulse height can be computed if the capacitance, detector characteristics, and radiation are known. The capacitance is normally about 10 4 farads. The number of ionizing events may be calculated if the detector size and specific ionization, or range of the charged particle, are known. The only variable is the gas amplification factor that is dependent on applied voltage. 

Any chamber map will be a function of its resolution. The resolution, in turn, is a function of the detector size and the number of points sampled. It is not unusual, as will be shown, for chamber maps of the same lamp design, to have two different mapping patterns. 

Concerns Regarding the Practice of Multiple Detector Size-Exclusion Chromatography... 

Many types of plastic scintillators are commercially available and find applications in fast timing, charged particle or neutron detection, as well as in cases where the rugged nature of the plastic (compared to Nal), or very large detector sizes, are appropriate. Sub-nanosecond rise times are achieved with plastic detectors coupled to fast photomultiplier tubes, and these assemblies are ideal for fast timing work. 

Either the user or the manufacturer must choose these parameters according to other requirements such as detector size, //, physical size, and so forth. It is common practice to splice several spectral segments to cover a wider spectral range, as will be discussed in Section 8.6. 

The imaging area for transmission and reflection measurements is consistent with the detector size (3.9 x 3.9mm ). For ATR-measurements, the imaging area is 3.9 X 5.5 mm because of the illumination geometry [37]. 

Detector size One factor that greatly affects the spatial resolution is the intrinsic resolution of the scintillation detectors used in the PET scanner. For multidetector PET scanners, the intrinsic resolution (Rf) is related to the detector size d. R, is normally given by d/2 on the scanner axis at midposition between the two detectors and by d at the face of either detector. Thus it is best at the center of the FOV and deteriorates toward the edge of the FOV. For a 6-mm detector, the Ri value is mm at the center of the FOV and 6mm toward the edge of the FOV. For continuous single detectors, however, the intrinsic resolution depends on the number of photons detected, not on the size of the detector, and is determined by the full width at half maximum of the photopeak. 

If the detector size is 8 mm, what is the expected approximate spatial resolution for 18F-FDG PET images at the center of the FOV ... 

It is instructive to rederive Eq. 8.7, not by using Eq. 8.4, but by a method that gives more insight into the relationship between detector size and source-detector distance. 

Effect of density and size of detector material. The efficiency of a detector will increase if the probability of an interaction between the incident radiation and the material of which the detector is made increases. That probability increases with detector size. But larger size is of limited usefulness because the background increases proportionally with the size of the detector, and because in some cases it is practically impossible to make large detectors. (Semiconductor detectors are a prime example.)... 

Photons and neutrons traversing a medium show an exponential attenuation (see Chap. 4), which means that there is always a nonzero probability for a photon or a neutron to traverse any thickness of material without an interaction. As a result of this property, detectors for photons or neutrons have efficiency less than 100 percent regardless of detector size and energy of the particle. 

The magnitude of the Compton continuum is also affected by the size of the detector (Fig. 12.2). The larger the detector is, the greater the probability of a second Compton interaction. If the detector size could become infinite, the Compton continuum would disappear. 

The efficiency increases with crystal size. The user should be aware, however, that when the detector volume increases, the background counting rate increases too. In fact, the background is roughly proportional to the crystal volume, while the efficiency increases with size at a slower than linear rate. Thus, there may be a practical upper limit to a useful detector size for a given experiment. 

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