Photomultiplier, solid-state

Detector Photomultiplier Solid state, charge transfer device... 

Por IR-Raman experiments, a mid-IR pump pulse from an OPA and a visible Raman probe pulse are used. The Raman probe is generated either by frequency doubling a solid-state laser which pumps the OPA [16], or by a two-colour OPA [39]. Transient anti-Stokes emission is detected with a monocliromator and photomultiplier [39], or a spectrograph and optical multichannel analyser [40]. 

Some properties of the detectors most commonly used for transmission experiments are summarized in Table 3.2. Alternative counters are scintillation detectors based on Nal or plastic material that is attached to a photomultiplier, and solid-state detectors using silicon- or germanium-diodes. 

R. W. Engstrom, Photomultiplier Handbook, RCA Solid State Division, Lancaster, Pennsylvania 17604 (1980). 

In this final section, we summarize the operation and characteristics of the principal vacuum tube and solid state detectors that are available for red/near-IR fluorescence studies. These include conventional photomultipliers, microchannel plate versions, streak cameras, and various types of photodiodes. Detector applicability to both steady-state and time-resolved studies will be considered. However, emphasis will be placed on photon counting capabilities as this provides the ultimate sensitivity in steady-state fluorescence measurements as well as permitting lifetime studies. 

There can be little doubt there is still much progress to be made in the application of solid-state detectors to the study of near-IR fluorescence. However, solid-state photomultipliers capable of replacing the conventional photomultiplier tube in mainstream fluorescence applications would still seem to be a long way away. 

Current instrumentation usually uses a diffraction grating as the dispersive element and a photomultiplier as the detector, although solid-state detectors are becoming more widespread. 

The availability of solid-state detectors (such as the charge-coupled detector, CCD) makes it possible to acquire simultaneously significant portions of the spectra or even the entire rich spectra obtained by ICP-OES in the UV-Vis region, thus providing a large amount of data. The commercial availability of ICP-OES instruments with these multichannel detectors has significantly renewed interest in this technique. However, some limitations, such as the degradation of the spectral resolution compared with photomultiplier-based dispersive systems, still remain. 

Other solid-state applications of silicon carbide include its use as an electroluminescent diode for use in sound recording equipment and photomultipliers and controllers. It has been studied as a reflective surface for lasers. By combining its excellent thermal conductivity and high electrical resistance, silicon carbide has also found application as an insulating material for integrated circuit substrates. 

A photomultiplier tube is a sensitive detector of visible and ultraviolet radiation photons cause electrons to be ejected from a metallic cathode. The signal is amplified at each successive dynode on which the photoelectrons impinge. Photodiode arrays and charge coupled devices are solid-state detectors in which photons create electrons and holes in semiconductor materials. Coupled to a polychromator, these devices can record all wavelengths of a spectrum simultaneously, with resolution limited by the number and spacing of detector elements. Common infrared detectors include thermocouples, ferroelectric materials, and photoconductive and photovoltaic devices. 

Figure 1 Block diagram of the solid-state dedicated CD spectrophotometer (J-800KCM). P polarizer M photoelastic modulator (PEM) S sample and rotation stage LI, L2 lenses A analyzer (Glan-Tayler) D photomultiplier (R376) MINI 12P sample stage controller lock-in ampl JASCO lock-in amp2 Stanford SRS 830 Recorder SEKO-NIC SS-250F PC personal computer.

Scintillation counters usually consist of a sodium iodide crystal doped with 1% thallium. The incident X-ray photons cause the crystal to fluoresce producing a flash of light for every photon absorbed. The size of the light pulse is proportional to the energy of the photon and is measured by a photomultiplier. A deficiency associated with scintillation counters is that they do not provide as good energy resolution as proportional or solid state detectors. 

The performance of the photomultiplier (representative of a very fast responding sensor even in terms of modern solid state devices) is shown in the lower curves and its performance is in complete contrast to that of the cadmium sulfide cell. The time constant, determined again from the slope of the log curve, was found to be only 40 milliseconds. Such a response time is generally acceptable for most GC and LC separations. Nevertheless in both fast GC and fast LC solutes can be eluted in less than 100 milliseconds in which case an... 

The basic components of spectrophotometers are a light source, wavelength selector, absorption cell (cuvette), and photodetector. Colorimeters or absorptiometers commonly use nondispersive wavelength selection (a filter with bandwidth 4 -40 nm) and solid state or simple phototube detectors, while spectrophotometers employ a prism or grating monochromator (with bandwidth down to 0.2 nm) and a photomultiplier. Colorimeters are inexpensive and most appropriate for repetitive measurements of absorption at a fixed wavelength. The more expensive spectrophotometer can also fulfill this function, but its main purpose, by virtue of its accurate and variable wavelength control, is the measurement of absorption spectra. 

Photographic emulsions and photoelectric detection devices can be used as detectors for electromagnetic radiation between 150 and 800 nm. Among the photoelectric devices, photomultipliers are the most important but new solid state devices have become a useful alternative. 

For the precise and quick measurement of radiant intensities but also of ion currents photoelectric techniques are used almost exclusively. The measurements can easily be automated. The detectors used are photomultipliers, electron multipliers, photodiode array detectors, camera systems and other solid state detectors. 

Mitchell G W, Hastings J W. A stable, inexpensive, solid-state photomultiplier photometer. Anal Biochem 1971 39 243-50. 

Optical spectroscopy ranging from Raman through Atomic is under considerable pressure to replace the "tried and true" photomultiplier tube (PMT) with multichannel devices. Two classes of solid state devices, the Charge Coupled Device (CCD) and the Charge Injection Device (CID), hold great promise for meeting this need. Operating modes of these devices are reviewed. Characteristics pertinent to analytical spectroscopy are presented. 

There arc several important differences between solid-state detectors, such as photodiodes, and vacuum devices, such as photomultipliers. These are highlighted in Table 1, from which it can be concluded that the choice between the two really depends on the type of analysis one wishes to carry out. Large, high-sensitivity instruments designed for the clinical laboratory invariably employ photomultipliers for detection. Recent innovations in photomultiplier design include the use of... 

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