Instrumentation multichannel analyzer

Energy Spectrometry (EDS) uses the photoelectric absorption of the X ray in a semiconductor crystal (silicon or germanium), with proportional conversion of the X-ray energy into charge through inelastic scattering of the photoelectron. The quantity of charge is measured by a sophisticated electronic circuit linked with a computer-based multichannel analyzer to collect the data. The EDS instrument is... 

The second-generation FOCS is shown in Figure 1. It consists of a He-Cd laser excitation source (Omnichrome model 139), a polychronator (Instruments SA model HR-320), an optical multichannel analyzer (either PAR-0MA2 or PAR-0MA3), and a coupler interface of the type described by Hirshfeld et al. (8) which couples the excitation light (4ill. 6 nm) into the optical fiber (Quartz Products QSF 1000) and... 

With analytical methods such as x-ray fluorescence (XRF), proton-induced x-ray emission (PIXE), and instrumental neutron activation analysis (INAA), many metals can be simultaneously analyzed without destroying the sample matrix. Of these, XRF and PEXE have good sensitivity and are frequently used to analyze nickel in environmental samples containing low levels of nickel such as rain, snow, and air (Hansson et al. 1988 Landsberger et al. 1983 Schroeder et al. 1987 Wiersema et al. 1984). The Texas Air Control Board, which uses XRF in its network of air monitors, reported a mean minimum detectable value of 6 ng nickel/m (Wiersema et al. 1984). A detection limit of 30 ng/L was obtained using PIXE with a nonselective preconcentration step (Hansson et al. 1988). In these techniques, the sample (e.g., air particulates collected on a filter) is irradiated with a source of x-ray photons or protons. The excited atoms emit their own characteristic energy spectrum, which is detected with an x-ray detector and multichannel analyzer. INAA and neutron activation analysis (NAA) with prior nickel separation and concentration have poor sensitivity and are rarely used (Schroeder et al. 1987 Stoeppler 1984). 

With single-photon exposure, excitations may decay either through a variety of processes including chain scission and fluorescence (47). We would therefore expect to observe fluorescence from two-photon excitation as well. To observe the fluorescence, we used a Spectra Physics mode locked dye laser system, operating with Rhodamine 560 dye. This was focused onto the polymer film, and the emitted light collected into a spectrometer with a Princeton Instruments Optical Multichannel Analyzer (OMA) attachment. 

Inductively Coupled Plasma. Analyses by ICP were performed on the same dissolutions used for the AA analyses for Cd and Pb. The solutions were diluted as necessary and were then nebulized and introduced into the plasma. Line spectra were collected with a multichannel analyzer and corrections were made for reagent blanks and background shifts. For all analyses, NBS Standard Reference Material 1632 was used for instrument calibration. 

C. The Basic Elements of the Experimental Setup. The basic elements of TRRR experiments are a photolysis source a laser probe source (whose scattered radiation by the photolabile sample contains the vibrational spectra of the photodecomposed sample and its transients) a dispersing instrument (e.g., a spectrometer) and an optical multichannel analyzer (OMA) system used as a detector. 

To acquire this information, the two displaced continuum beams are imaged with a cylindrical and a spherical lens onto different positions along the length of the entrance slit of a low dispersion spectrograph (Instruments SA, model UFS-200). The two resulting parallel dispersed spectra are fully separated from each other at the focal plane, where they are detected by the model 1254 SIT detector head of an EG + G Princeton Applied Research Corporation optical multichannel analyzer system. In conjunction with a model 1216 detector controller and model 1215 console, this detector is programmed with a two dimensional... 

In summary, we have combined state of the art optical multichannel analyzer techniques with well established low repetition rate picosecond laser technology to construct an instrument capable of measuring transient spectra with unprecedented reliability. It is, in its present form, a powerful tool for the investigation of ultrafast processes in biological, chemical, and physical systems. We foresee straightforward extension of the technique to the use of fourth harmonic excitation (at 265 nm) and also a future capability to study gaseous as well as condensed phase samples over a more extended spectral range. 

Spectrex ILI-1000 Particle Counter combines the Prototron with a Particle Profile Attachment (multichannel analyzer). The instrument has been used [118] for examining volcanic ash. AC Fine Dust was used for calibration in eight 5 pm steps, which indicated that accurate data was obtained for sizes above 2 pm. It has also been shown to correlate well with the more tedious filtration and counting method for large volume parenteral liquids [119]. Although semi-transparent containers or liquids reduce the amount of transmitted light flux, the instrument gives valid data for particulates in oil [120]. 

Cu (5.1 min). Instrumental radioassay was performed with a similar nuclear counting system as for the airborne gunshot residues (Ref 17) described above with the addition of a programmable computer coupled to the multichannel analyzer for data processing. Using these procedures, it was possible to detect Ba levels above 2 x 10 g/cm and Sb levels above 1.5 x 10" g/cm of floor surface... 

A large number of routine clinical chemistry laboratories perform analyses with multichannel analyzers of both the continuous-flow and the direct-sample type. Various types of spectrophotometric reference materials have been recommended to validate the photometric accuracy and linearity, wavelength accuracy or stray light radiation of photometric systems used for clinical analyses. In this respect, much has been done in the national area. The problem we are facing now concerns the required reference materials to be used for the validation of the concentration accuracy of this instrumentation, so widely used in clinical chemistry laboratories. 

Another non-photographic instrument for GED studies was build by Schafer and coworkers at the University of Arkansas in 1984 [24]. In this machine the scattered electrons are detected by a fluorescent screen, which is optically coupled to a custom multichannel analyzer. Later several improvements were introduced into the original design [25-27] and the possibility of using real-time GED as a detector in gas chromatography was demonstrated [28]. Some recent studies of SF [29] and Sep6 [30] show the application of this procedure. 

We employ method B to study effects of this type. In this mode, our apparatus yields relative high-resolution fluorescence spectra at different time windows after excitation of the sample by the 355 nm pulse. The spectra are acquired by the upconversion method. The upconverted fluorescence spectrum is recorded simultaneously at all monitored wavelengths by an optical multichannel analyzer. It is constructed from a poly-chromator (HR320 Instruments SA) and an intensified silicon photodiode array detector (Princeton Applied Research Model 1412). The detector is interfaced to our Cromemco computer. 

Continuous-flow instruments may also be single-channel (batch) instruments that analyze a continuous series of samples sequentially for a single analyte (Figure 23.4). Or they may be multichannel instruments in which the samples are split at one or more points downstream into separate streams for different analyte analyses, or separate ahquots of samples may be taken with separate streams in parallel. 

The measurements were performed with an usual setup for siuface-enhanced Raman spectroscopy The Raman spectra were measured with a Spex 1406 spectrometer, the samples were illmninated with a Spectroscopy Instruments argon ion laser (A = 514 nm, 30 mW) and the spectra were detected by a Princeton Instruments optical multichannel analyzer imder computer control. All experiments were performed in an electrochemical cell containing an inert platinum working electrode mechanically... 

To measure an energy spectrum of a radioactive source means to record the pulse-height distribution produced by the particles emitted from the source, which is achieved with the use of an instrument called the multichannel analyzer (MCA). Multichannel analyzers are used in either of two different modes the pulse-height analysis (PHA) mode or the multichannel scaling (MCS) mode. 

Figure 12.25 (a) Ge detector with its cryostat and multichannel analyzer (reproduced from Instruments for Research and Applied Sciences by permission of EG G ORTEC, Oak Ridge, Tennessee). (b) Portable Ge detector system with its cryostat and multichannel analyzer (courtesy of Canberra Nuclear). 

In activation analysis advantage is taken of the fact that the decay properties such as the half-life and the mode and energy of radioactive decay of a particular nuclide serve to identify uniquely that nuclide. The analysis is achieved by the formation of radioactivity through irradiation of the sample either by neutrons or charged particles. Neutron irradiation is by far the more common technique, and hence this method is often referred to as neutron activation analysis, NAA. A major advantage in activation analysis is that it can be used for the simultaneous determination of a number of elements and complex samples. If the counting analysis of the sample is conducted with a Ge-detector and a multichannel analyzer, as many as a dozen or more elements can be measured quantitatively and simultaneously (instrumental NAA, or INAA). 

A significant improvement to LS instrumentation was summing the pulses from each PMT for an output proportional to the total intensity of the scintillation event. This design for an LS system with pulse coincidence detection and summation (Fig. 8.5) has remained basically unchanged over the last forty years. More recently, instrument vendors have replaced a traditional three-channel system with a multichannel analyzer (MCA) and software for spectral analysis. 

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