Photodiode detectors

Some radiation detectors, i.e., photoemissive detectors (vacuum phototubes or photomultipliers) or semiconductor detectors (photodiodes or phototransistors) directly produce an electrical signal by quantum effects. Their output is strongly dependent on the wavelength of the detected radiation. Thermal detectors, i.e., thermocouples and thermopiles, bolometers, pyroelectric detectors, or pneumatic and photoacoustic detectors record a temperature increase through radiation and convert this into an electrical signal. This is proportional to the flux of the absorbed radiant power, independent of the wavelength. 

Variable-wavelength detector using a deuterium or tungsten lamp with wavelength selection by a monochromator Filter photometer using a deuterium lamp with wavelength selection by filters Scanning ultraviolet (UV) detector Photodiode array detector... 

For purposes of luggedness and simplicity, it is desirtible to replace PMTs by solid-state detectors. Photodiodes provide a high-speed response and wide spectral sensitivity. Avalanche photodiodes even provide an internal gain of about 100-fold. However, the lack of high amplification and the small active area limit their usefulness for high-sensitivity detection. 

Refractive index (RI) detector Ultraviolet (UV) detector Photodiode array detector (DAD)... 

In addition to phototubes, other transducers such as oxygen electrodes, flame ionization detectors, photodiodes, and photomultiplier tubes produce output currents related to concentration or to a physical phenomenon of interest. The current follower is an indispensable circuit for measuring the small currents produced. 

Debye-Bueche function, 178 Debye-Waller factor, 20, 24 densification aerogels, 216 process, 70 silica xerogels sound velocity, 104 thermal treatment effect, 101 density measurement, 191 deposition methods dip-coating, 66 spin, 66 detectors photodiodes, 23 scintillation, 23... 

This is actually the increase of the dark current due to illumination and is a dc value (valid for/= 0 Hz). Here rj denotes the quantum efficiency of the detector, < ) is the incident photon flux density, A is the detector active area. The factor T denotes the photoelectric gain or photogain (the ratio between the number of electrons flowing through the electric circuit and the number of absorbed photons). The fundamental equation of photoconductivity is also valid without changes for the short circuit current of a photovoltaic detector (photodiode operating in photo-conductive mode). In that mode of operation T = 1 in most of the cases. 

The discrepancies can be explained by the fact that sometimes, for laminar velocity measurements done by the constant volume container method at elevated initial pressure, high-speed ScUieren photography was not used the visible flame velocity was found either from the pressure records or from data on the front arrival time to a certain position (flame-ionization detectors, photodiodes). The experiments in [26] and [41] were performed in such a manner. 

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