Resolution scanning multichannel

Figure 1, Top High time-resolution data [scan, multichannel scaling (MCS) mode] recorded by the on-hoard bioluminescence detector in the Gulf of Alaska. The signal intensity has been attenuated with a neutral-density 3 filter (1000 X attenuation) inserted between the viewing chamber window and face of the photocathode of the PMT.

Optical emision spectra nowadays are simply measured using a fiber optic cable that directs the plasma light to a monochromator, which is coupled to a photodetector. By rotating the prism in the monochromator a wavelength scan of the emitted light can be obtained. Alternatively, an optical multichannel analyzer can be used to record (parts of) an emission spectrum simultaneously, allowing for much faster acquisition. A spectrometer resolution of about 0.1 nm is needed to identify species. 

Large molecules exacerbate this problem, increasing the length of the mass scale. Further, for high resolution measurements the fraction of the mass scale measured at any time must be much smaller. For MS/MS these scanning problems are increased exponentially, as measurement of MS-II spectra can be necessary for a multiplicity of primary ion species separated by MS-I (6). Multichannel detection is an obvious solution to this problem. Array... 

Recent advances in solid state detectors have led to more efficient laser Raman spectrometers. These spectrometers are based on multichannel detectors (MCD) and are at least an order of magnitude faster than the systems based on PMT detector. However, at present these systems do not match the resolution capabilities of the scanning systems. The Spex Triplemate 1877 A is a new generation instrument which can be fitted with an intensified diode array consisting of 1024 elements. Figure 4.6.3 shows spectra obtained with these two types of detectors. 

There are different types of spectrometers with detector arrays. Due to the limited number (256, 512 or 1024) of available detector elements compared to the number of resolvable spectral elements, the spectrometers permit either low resolution over the entire spectral range, or high re.solution within a limited range. Alternatively, the technique described by Knoll et al. (1990) may be used They employed scanning a multichannel instrument, which combines the merits of the scanning technique with those of the multichannel technique. 

This investigation is based on data of the Advanced Very High Resolution Radiometer operated on the weather satellite series of the National Oceanic and Atmospheric Administration of the United States of America. The first instrument was launched in 1978. Three versions of the multichannel scanning radiometer were operated at 13 satellites and measured in 5-6 channels in the visible, near-infrared and thermal infrared spectral range, as defined in Table 9.1. 

Why does multichannel PDA detection exhibit such improved signal to noise over single channel pmt detection A major factor is clearly that the signal averaging intergration time of each of 170 resolution elements in the PDA case is the full acquisition time, i.e., 60 seconds, while the acquisition time for the PMT experiments is a small fraction, 1/20, of the total acquisition time due to the necessity of scanning for single channel detection. 

Spectrometer 1 is based on a linear self-scanned image sensor, capable of providing a 10 ms per spectrum, scan time. This spectrometer was borne by the S-310-8 rocket, which was launched from Kagoshima Space Center (131°04 45"E, 31°15 00"N) at 17 47 JST (Japan Standard time, 135°E) on February 2, 1980. The spectrometer, that measured the NIR absorption of atmospheric constituents such as and H 0, was according to our knowledge the first rocket-borne multichannel spectrometer capable of measuring spectra with an altitude resolution better than 2 km. 

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