Signal detectors photomultipliers

There are two ways to collect FLIM data freqnency-domain or time-domain data acqnisition (Alcala et al. 1985 Jameson et al. 1984). Briefly, in freqnency domain FLIM, the fluorescence lifetime is determined by its different phase relative to a freqnency modulated excitation signal nsing a fast Fourier transform algorithm. This method requires a frequency synthesizer phase-locked to the repetition freqnency of the laser to drive an RF power amplifier that modulates the amplification of the detector photomultiplier at the master frequency plus an additional cross-correlation freqnency. In contrast, time-domain FLIM directly measures t using a photon connting PMT and card. 

Scintillators are also used in the detectors of CT scanners. Here an electronic detector, the photomultiplier tube, is used to produce an electrical signal from the visible and ultraviolet light photons. These imaging systems typically need fast scintillators with a high efficiency. 

Direct-reading polychromators (Figure 3b) have a number of exit slits and photomultiplier tube detectors, which allows one to view emission from many lines simultaneously. More than 40 elements can be determined in less than one minute. The choice of emission lines in the polychromator must be made before the instrument is purchased. The polychromator can be used to monitor transient signals (if the appropriate electronics and software are available) because unlike slew-scan systems it can be set stably to the peak emission wavelength. Background emission cannot be measured simultaneously at a wavelength close to the line for each element of interest. For maximum speed and flexibility both a direct-reading polychromator and a slew-scan monochromator can be used to view emission from the plasma simultaneously. 

A sealed-tube neutron generator, utilizing the deuterium-tritium reaction is the source of fast (14 MeV) neutrons, and a 8 x 3 1 Nal scintillation detector, with three optically coupled photomultipliers, is used to measure the >ray signal... 

When measuring a signal, one records the magnitude of the output or the response of a measurement device as a function of an independent variable. For instance, in chromatography the signal of a Flame Ionization Detector (FID) is measured as a function of time. In spectrometry the signal of a photomultiplier or diode array is measured as a function of the wavelength. In a potentiometric titration the current of an electrode is measured as a function of the added volume of titrant. 

The recognition of the importance of MP in maintaining the health of the retina has led to the development of a number of methods for determining its concentration in situ. These methods, necessarily noninvasive, are routinely employed in dietary supplementation studies with lutein or zeaxanthin to monitor the uptake of the carotenoids into the retina. Every method exploits the optical properties of lutein and zeaxanthin, specifically their absorbance at visible wavelengths. The detection of a light signal, modified by the carotenoids, is accomplished either by the retinal photoreceptors themselves (psychophysical methods) or by a physical detector such as a photomultiplier,... 

Our first chapter in this set [4] was an overview the next six examined the effects of noise when the noise was due to constant detector noise, and the last one on the list is the first of the chapters dealing with the effects of noise when the noise is due to detectors, such as photomultipliers, that are shot-noise-limited, so that the detector noise is Poisson-distributed and therefore the standard deviation of the noise equals the square root of the signal level. We continue along this line in the same manner we did previously by finding the proper expression to describe the relative error of the absorbance, which by virtue of Beer s law also describes the relative error of the concentration as determined by the spectrometric readings, and from that determine the... 

The secondary electrons emitted from the sample are attracted to the detector by the collector screen. Once near the detector, the secondary electrons are accelerated into the scintillator by a positive potential maintained on the scintillator. Visible light is produced by the reaction of the secondary electrons with the scintillator material. The emitted light is detected by a photomultiplier tube, which is optically coupled to the scintillator via a light pipe. The PMT signal is then transferred to the grid of a cathode ray tube (CRT). Data collection... 

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