Spectrum analyzer

About: Spectrum analyzer is a(n) research topic. Over the lifetime, 12217 publication(s) have been published within this topic receiving 101851 citation(s).

Experimental Test of Bell's Inequalities Using Time- Varying Analyzers

Abstract: Correlations of linear polarizations of pairs of photons have been measured with time-varying analyzers. The analyzer in each leg of the apparatus is an acousto-optical switch followed by two linear polarizers. The switches operate at incommensurate frequencies near 50 MHz. Each analyzer amounts to a polarizer which jumps between two orientations in a time short compared with the photon transit time. The results are in good agreement with quantum mechanical predictions but violate Bell's inequalities by 5 standard deviations.

Mass cytometry: technique for real time single cell multitarget immunoassay based on inductively coupled plasma time-of-flight mass spectrometry.

Abstract: A novel instrument for real time analysis of individual biological cells or other microparticles is described. The instrument is based on inductively coupled plasma time-of-flight mass spectrometry and comprises a three-aperture plasma−vacuum interface, a dc quadrupole turning optics for decoupling ions from neutral components, an rf quadrupole ion guide discriminating against low-mass dominant plasma ions, a point-to-parallel focusing dc quadrupole doublet, an orthogonal acceleration reflectron analyzer, a discrete dynode fast ion detector, and an 8-bit 1 GHz digitizer. A high spectrum generation frequency of 76.8 kHz provides capability for collecting multiple spectra from each particle-induced transient ion cloud, typically of 200−300 μs duration. It is shown that the transients can be resolved and characterized individually at a peak frequency of 1100 particles per second. Design considerations and optimization data are presented. The figures of merit of the instrument are measured under standard indu...

Laser frequency stabilization by polarization spectroscopy of a reflecting reference cavity

Abstract: We propose a new scheme for locking the frequency of a laser to a resonant reference cavity A linear polarizer or Brewster plate is placed inside the reference cavity, so that the reflected light acquires a frequency-dependent elliptical polarization A simple polarization analyzer detects dispersion shaped resonances which can provide the error signal for electronic frequency stabilization without any need for modulation techniques

Electrical low pressure impactor

Abstract: Electrical detection is used for the first time to achieve real-time operation of a low pressure cascade impactor. An instrument is developed using Berner type multijet low pressure impactor stages with minimum modification. The cut-sizes of the seven channel system range from 0.030 to 1.0 μm. A multichannel electrometer is constructed using low cost monolithic electrometer operational amplifiers. The zero-check technique is applied to achieve a lowest detectable current of 10 fA, less than a tenth of the input bias current of the operational amplifiers. The time resolution is 1 min in the lock-in mode and 1 s in the high concentration mode. The sensitivity and size resolution of the instrument are comparable to the corresponding values of the Electrical Aerosol Analyzer. The feasibility of the instrument in measuring submicron number size distribution has been tested by comparison measurements with a differential mobility analyzer. The results show quantitative agreement.

Delayed extraction matrix‐assisted laser desorption time‐of‐flight mass spectrometry

Abstract: A new delayed extraction matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometer system is described which provides dramatically improved performance over that obtained with identical TOF analyzers operated with constant electrical fields In this system the ions formed by MALDI are produced in a weak electrical field, and subsequently extracted by application of a high voltage pulse after a predetermined time delay Three parameters can be independently adjusted to optimize the performance These include the field magnitude and direction during and immediately following ion production, the magnitude of the extraction field, and the time delay between the laser pulse and application of the extraction field Theoretical equations are presented which guide the selection of these parameters to optimize the performance Results are presented from three TOF analyzers of similar design, but ranging in size from a 13 m linear analyzer to a 64 m reflector In all cases delayed extraction provides substantially improved resolution over that obtained from static operation In the smallest linear analyzer resolution of M/ΔM (full width at half maximum) of 4000 is demonstrated for angiotensin I, and with the largest reflecting analyzer, the isotope peaks of bovine insulin are resolved nearly to baseline With larger proteins, the isotopic peaks are not resolved, but resolution approaching the width of the isotopic envelope is obtained Resolution improvement is demonstrated for proteins up to 30 kDa In addition to improved resolution, delayed extraction is shown to improve the quality of MALDI mass spectra by suppressing matrix background, reducing chemical noise, and minimizing the effect of laser intensity on performance