A Fabry-Perot interferometer/grating monochromator combination for high resolution optical spectroscopy

Optical multichannel analyzer as a scanner for the ultracentrifuge: I. Single beam operation

Effects of magnetic fields with different intensities on laser-induced plasmas were investigated. Plasmas were formed in air by KrF eximer laser ablation of graphite (C), copper (Cu) and lead targets (Pb). Transverse magnetic fields were applied to the plasmas using two permanent magnets. Optical signals from the plasmas were collected both by an ultrafast phototube and an optical multi-channel analyzer (OMA) system. The full width at half maximum (FWHM) of the signals captured by an oscilloscope connected to the phototube were taken as a measure of the plasmas lifetimes. Time-resolved spectra captured by the OMA system were analyzed to observe the decay of specific spectral lines of the ionic forms of C, Cu, and Pb. The results were analyzed to gain an understanding of the relationship between magnetic confinement of laser-induced plasmas and the atomic masses of the substrate materials.Effects of magnetic fields with different intensities on laser-induced plasmas were investigated. Plasmas were formed in air by KrF eximer laser ablation of graphite (C), copper (Cu) and lead targets (Pb). Transverse magnetic fields were applied to the plasmas using two permanent magnets. Optical signals from the plasmas were collected both by an ultrafast phototube and an optical multi-channel analyzer (OMA) system. The full width at half maximum (FWHM) of the signals captured by an oscilloscope connected to the phototube were taken as a measure of the plasmas lifetimes. Time-resolved spectra captured by the OMA system were analyzed to observe the decay of specific spectral lines of the ionic forms of C, Cu, and Pb. The results were analyzed to gain an understanding of the relationship between magnetic confinement of laser-induced plasmas and the atomic masses of the substrate materials.

A microprocessor system and interface for the optical multichannel analyzer (OMA) is described. The interface hardware and software are very simple and easy to implement. The microcomputer is used in conjunction with the OMA in the 2-d (two-dimensional) mode as the data acquisition, analysis and storage system for a 8-ps-resolution transient absorption spectrometer. However, the microcomputer and interface hardware and software are of general use in any application where rapid transfer, processing and storage of spectroscopic information from the OMA are required.

Along with rapid development of semiconductor, photodetector arrays (e.g. CCD) have offered the great promise of compact Optical Multichannel Analyzer (OMA) for spectrum fast measurements in a variety of applications. It deserves to pay attention to frequency response of electronic circuit in OMA, otherwise it will impair the spectrum resolving power of the analyzer. In this paper, we present a detailed frequency analysis of electronic circuit in OMA, and find that the frequency response should be met a severe condition, in which the cutoff frequency is much higher than the output frequency of photodetector arrays, to guarantee the resolution performing well in OMA.

A computer interface for a PARC model 1205A Optical Multichannel Analyzer (OMA) is described. This interface uses the output from the OMA’s internal analog-to-digital converter rather than the usual parallel I/O facility. The ADC output is transmitted from the OMA to the computer over a single 75-Ω coax cable. Since the data obtained from each OMA scan may be stored in the computer memory, extremely versatile processing algorithms may be used, and normal OMA operation is not affected. The software used is also described.

An investigation of the accuracy of Doppler broadened line profile analysis applied to plasma diagnostics

The development of optical multichannel analyzer techniques for UV/VIS spectroscopy is presented. The research focuses on the development of spectroscopic techniques for measuring high resolution spectral lineshape functions from the exciton phosphorescence in H/sub 2/-1,2,4,5-tetrachlorobenzene. It is found that the temperature dependent frequency shifts and widths confirm a theoretical model based on an exchange theory. The exchange of low energy phonon modes which couple with excited state exciton transitions is shown to display the proper temperature dependent behavior. In addition to the techniques for using the optical multichannel analyzer (OMA) to perform low light level target integration, the use of the OMA for capturing spectral information in transient pulsed laser applications is discussed. An OMP data acquisition system developed for real-time signal processng is described. Both hardware and software interfacing considerations for control and data acquisition by a microcomputer are described. The OMA detector is described in terms of the principles behind its photoelectron detection capabilities and its design is compared with other optoelectronic devices.

Based on the inherent molecular structure characteristics of the OH radicals, the energy level distribution, the transition frequency and Einstein spontaneous emission transition probability are systematically analyzed and numerically studied. Meanwhile, combined with the spectra experiments, the natural broadening, collision broadening, Doppler broadening and instrumental broadening effects on spectral line shape are analyzed. The dependence of the spectral profile on the rotational temperature, the vibrational temperature, and the spectral function are numerically explored in certain ranges. The corresponding numerical results are also discussed for the emission spectra thermometry, which provides a theoretical basis for the emission thermometry. In experimental, the emission spectra of OH (A2Σ+→X2Πr) system of the hydrogen flames are recorded by the optical multi-channel analyzer and studied. By the fitting of the experimental spectra to the numerically calculated spectra, the corresponding rotational and vibrational temperatures of the hydrogen flames are determined, respectively.

The authors describe the hardware and software they have realized to control an optical multichannel analyzer (OMA) by a standard 16-bit microcomputer. The hardware consists of an interface card plugged into the microcomputer and connected to the OMA system. The software gives complete control over the OMA and adds powerful functions to the system, like various graphic representations of spectra taken by the OMA, storage of spectra on floppy disks, direct computation on the spectra, and a complete control of spectroscopy experiments.

The development of a special optical multichannel analyzer (OMA) has been finished in the frames of a COPERNICUS project. The aim of our present work is to recall the attention to some of the unique benefits of 2D CCD detector matrices in OMAs in contrast to the usual line detectors. We demonstrate the relatively simple hardware and software reconfiguration possibilities of our new OMA system to achieve the establishment of a problem oriented, neural network evaluated, low cost multichannel analyzer.

Zeeman splitting of spectral lines from hydrogen and impurities in the JET Tokamak plasma has been observed in the visible region of the spectrum. An Optical Multichannel Analyser (OMA) coupled to a 1 m Czerny-Turner instrument is used to record several spectral lines simultaneously many times during a discharge. Tangential viewing optics enhance the influence of Zeeman splitting, especially when the impurities are located where the magnetic field is aligned along the viewing chord. To date, splitting of Halpha (6563 AA), CII (6578 AA and 6583 AA), CrI (4289 AA, 4274 AA and 4254 AA) and CIII (4794 AA, 4810 AA and 4819 AA) has been detected. The location of the impurities is determined from the magnitude of the splitting and the known toroidal field distribution. The effects of the magnetic field on the line profiles are best observed during the plasma initiation and termination phases where, for example, a large plasma incursion can result in the injection of impurities from the inner wall. The technique is of particular importance in determining the source of impurities (e.g. from the inside wall or the limiter at the outer periphery). The observations also highlight the importance of taking Zeeman splitting into account when making Doppler shift or broadening measurements in the visible spectrum.

UV laser induced fluorescence of unirradiated and irradiated low density polyethylene

A 16-bit microcomputer has been coupled to an optical multichannel analyser (OMA). This paper describes the hardware interface which has been developed so as to permit the transfer of spectra in both directions, from the OMA into the RAM extension memory of the microprocessing system, and back from there into either one memory of the OMA. A few elementary circuit modifications of the OMA itself are required to allow that back transfer, and are also described. A brief outline of the software is given. The adjunction of the microcomputer to the OMA makes it possible to operate this instrument in a new mode: real time with optical integration and nevertheless without any baseline.

A novel method to combine a microscope and an optical multichannel analyzer (OMA) into a microspectrophotometer (MSP) system is presented. In this system, an optical fiber was mounted into the image plane of the microscope both to collect light from the microscope and transmit it to the OMA for spectral analysis, as well as to conduct light in the reverse direction into the microscope for alignment purposes. The system is easy to construct, is simple to use, and has a higher spectral resolution than conventional MSPs without increasing the acquisition time. Its sensitivity depends on the photodetector used in the OMA. For the two application examples presented, (1) absorbance spectrum measurements of cytoplasm and nuclear areas of Papanicolaou-stained cervical cells and (2) autofluorescence spectrum measurements of different locations of unstained and unfixed skin tissue sections, this system was found to possess adequate sensitivity.

Association of a 16-bit microprocessor with an optical multichannel analyzer