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Sensitive detection of tunable diode laser absorption by polarization rotation

Description: Results are presented demonstrating that diode laser absorption sensitivity can be increased by using the Faraday or Kerr effect to rotate the polarization of the source so that crossed polarizers can be used to reduce source noise. The Faraday effect is demonstrated using nitrous oxide in a magnetic field, and the Kerr effect is demonstrated using methyl fluoride in an electric field. Some description of how absorption in an external field causes polarization rotation is presented as well as some conclusions on the types of molecules for which this technique is best suited.
Date: January 1, 1985
Creator: Loge, G.W.; Laguna, G.A. & Hartford, A.
Partner: UNT Libraries Government Documents Department

Detection of photon bursts from single 200 eV Mg ions: Progress in photon burst mass spectrometry

Description: Modern atom counting methods, based on advances in laser and accelerator technology, provide a valuable complement to traditional decay counting methods for radioisotope dating and tracer work. Tandem Accelerator Mass Spectrometry (TAMS) has already had a large impact on /sup 14/C dating and is beginning to provide new opportunities with /sup 10/Be and several other isotopes. We report here on progress in the development of a laser-based technique, Photon Burst Mass Spectrometry, which is potentially capable of analyzing many of the elements which are forbidden in TAMS because they do not form negative ions. We are especially interested in the noble gases, which have a variety of potential scientific and environmental applications.
Date: January 1, 1989
Creator: Fairbank, W.M. Jr.; LaBelle, R.D.; Keller, R.A. & Chamberlin, E.P.
Partner: UNT Libraries Government Documents Department

Dual-beam, second-derivative tunable diode-laser infrared spectroscopy applied to trace-gas measurement

Description: A dual beam diode laser spectrometer has been constructed using off-axis reflective optics. The spectrometer can be amplitude modulated for direct absorption measurements or frequency modulated to obtain derivative spectra. The spectrometer has high throughput, is easy to operate and align, provides good dual beam compensation, and has no evidence of the interference effects that have been observed in diode laser spectrometers using refractive optics. Unpurged, using second derivative techniques, the instrument has measured 108 parts-per-million CO (10 cm absorption cell, atmospheric pressure-broadened) with good signal/noise. With the replacement of marginal instrumental components, the signal/noise should be substantially increased. This instrument was developed to monitor the evolution of decomposition gases in sealed containers of small volume at atmospheric pressure.
Date: April 1, 1981
Creator: Tallant, D. R. & Jungst, R. G.
Partner: UNT Libraries Government Documents Department

Quantitative SIMS analysis of decalibrated Chromel versus Alumel thermocouples using indexed sensitivity factors

Description: Secondary ion mass spectrometry (SIMS) is used to determine the failure mode responsible for the large decalibrations observed in sheathed, MgO-insulated Chromel versus Alumel, compacted thermocouple assemblies, exposed to temperatures above 1100/sup 0/C. Thermocouples sheathed in Inconel-600 and type 304 stainless steel were studied in this work. Quantified SIMS data showed that the observed decalibrations were due to significant alterations that took place in the Chromel and Alumel thermoelements. The amount of alteration was different for each thermocouple and was influenced by the particular sheath material used in the thermocouple construction.
Date: January 1, 1979
Creator: Christie, W.H.; Eby, R.E. & Kollie, T.G.
Partner: UNT Libraries Government Documents Department

Process, product, and waste-stream monitoring with fiber optics

Description: Fiber optic technology, motivated by communications and defense applications, has advanced significantly the past ten years. In particular, advances have been made in visible radiation transmission efficiency with concurrent reductions in fiber size, weight, and cost. Researchers at the Lawrence Livermore National Laboratory (LLNL) coupled these advances in fiber optic technology with analytical fluorescence analysis to establish a new technology - remote fiber fluorimetry (RFF). Laser-based RFF offers the potential to measure and monitor from one central and remote laboratory, on-line, and in near real time, trace (ppM) to substantial (g/L) concentrations of selected chemical species in typical process, product, and waste streams. The fluorimeter consists of a fluorescence or Raman spectrometer; unique coupling optics that separates input excitation (laser) radiation from return (fluorescence) radiation; a fiber optic cable; and an optrode - a terminal that interfaces the fiber to the measurement point, which is designed to respond quantitatively to a particular chemical species. At LLNL, research is underway into optrodes that measure pressure, temperature, and pH and those that detect and quantify various actinides, sulfates, inorganic chloride, hydrogen sulfide, aldehydes, and alcohols.
Date: October 10, 1983
Creator: Milanovich, F.P. & Hirschfeld, T.
Partner: UNT Libraries Government Documents Department

Atomic absorption spectrometer readout and data reduction using the LSI-11 microcomputer

Description: Some common instruments found in the chemistry laboratory have analog chart recorder output as their primary data readout media. Data reduction from this medium is slow and relatively inaccurate. This paper describes how to interface a single LSI-11 microcomputer to PERKIN-ELMER models 603 and 303 Atomic Absorption Spectrophotometers.
Date: November 27, 1978
Creator: Allen, M.J. & Wikkerink, R.W.
Partner: UNT Libraries Government Documents Department

Laser post-ionization secondary neutral mass spectroscopy

Description: Three different instruments using laser ionization techniques will be described. Results from the SARISA instrument with a demonstrated figure of merit of .05 (atoms detected/atoms sputtered) for resonance ionization; detection of Fe at the sub-part-per-billion level in ultrapure Si; and features of the instrument such as energy and angle refocusing time-of-flight (EARTOF) mass spectrometer and multiplexing for simultaneous detection of secondary ions and neutrals. 12 refs., 3 figs.
Date: January 1, 1987
Creator: Gruen, D.M.; Pellin, M.J.; Calaway, W.F. & Young, C.E.
Partner: UNT Libraries Government Documents Department

Simultaneous mass detection for direct inlet mass spectrometry

Description: The evolution of analytical techniques for application in trace analysis has led to interest in practical methods for real-time monitoring. Direct inlet mass spectrometry (DIMS) has been the subject of considerable activity in recent years. A DIMS instrument is described which consists of an inlet system designed to permit particles entrained in the inlet air stream to strike a hot, oxidized rhenium filament which serves as a surface ionization source. A mass analyzer and detection system then permits identification of the elemental composition of particulates which strike the filament.
Date: May 1, 1979
Creator: Gordon, R.L.
Partner: UNT Libraries Government Documents Department

Ultra-high-vacuum double-axis goniometer for use with an electron spectrometer

Description: A double-axis goniometer designed for moving and indexing an electon spectrometer for angle-resolved photoemission studies is described. A feature of the design is that the two rotations operate independently and either can be carried out with the analyzer at any position. The goniometer is designed to be installed in a 14'' spool piece which makes it possible to add it to an existing 14'' uhv system.
Date: January 1, 1981
Creator: Shleifer, M. & Williams, G.P.
Partner: UNT Libraries Government Documents Department

Two dimensional CCD (charged coupled device) arrays as parallel detectors in electron energy loss and x-ray wavelength dispersive spectroscopy

Description: Parallel detection systems for spectroscopy have generally been based upon linear detector arrays. Replacing the linear arrays with two dimensional systems yields more complicated devices; however, there are corresponding benefits which can be realized for both x-ray and electron energy loss spectroscopy. The operational design of these systems, as well as preliminary results from the construction of such a device used for electron spectroscopy, are presented. 10 refs., 8 figs.
Date: August 1, 1988
Creator: Zaluzec, N.J.
Partner: UNT Libraries Government Documents Department

Photoelectron spectrometer for high-resolution angular resolved studies

Description: We report on a new electron spectrometer system designed for use on storage-ring light sources. The system features a large (76 cm dia. x 92 cm long) triply magnetically shielded vacuum chamber and two 10.2 cm mean radius hemispherical electron-energy analyzers. One of the analyzers is fixed and the other is rotatable through about 150/sup 0/. The chamber is pumped by a cryopump and a turbomolecular pump combination so as to enable experiments with a variety of gases under different conditions. The light detection includes both a direct beam monitor and polarization analyzer. The electron detection is accomplished with either a continuous-channel electron multiplier or with multichannel arrays used as area detectors.
Date: January 1, 1982
Creator: Parr, A.C.; Southworth, S.H.; Dehmer, J.L. & Holland, D.M.P.
Partner: UNT Libraries Government Documents Department

Normal emission photoelectron diffraction: a new technique for determining surface structure

Description: One technique, photoelectron diffraction (PhD) is characterized. It has some promise in surmounting some of the problems of LEED. In PhD, the differential (angle-resolved) photoemission cross-section of a core level localized on an adsorbate atom is measured as a function of some final state parameter. The photoemission final state consists of two components, one of which propagates directly to the detector and another which scatters off the surface and then propagates to the detector. These are added coherently, and interference between the two manifests itself as cross-section oscillations which are sensitive to the local structure around the absorbing atom. We have shown that PhD deals effectively with two- and probably also three-dimensionally disordered systems. Its non-damaging and localized, atom-specific nature gives PhD a good deal of promise in dealing with molecular overlayer systems. It is concluded that while PhD will never replace LEED, it may provide useful, complementary and possibly also more accurate surface structural information.
Date: May 1, 1980
Creator: Kevan, S.D.
Partner: UNT Libraries Government Documents Department

Computer programs in BASIC language for atomic absorption flame spectroscopy. Part 1. Operating instructions. [Semiautomatic, random, and bracket codes]

Description: These instructions describe how to use three BASIC language programs to process data from atomic absorption spectrophotometers operated in the flame mode. These programs will also control an automatic sampler if desired. The instructions cover loading the programs, responding to computer prompts, choosing among various options for processing the data, operating the automatic sampler, and producing reports. How the programs differ is also explained. Examples of computer/operator dialogue are presented for typical cases.
Date: September 30, 1977
Creator: Boyle, W.G. Jr.
Partner: UNT Libraries Government Documents Department

Computer automation of continuous-flow analyzers for trace constituents in water. Volume 4. Description of program segments. Part 3. TAASTART

Description: This report describes TAASTART, the third program in the series of programs necessary in automating the Technicon AutoAnalyzer. Included is a flow chart that illustrates the program logic and a description of each section and subroutine. In addition, all arrays, variables and strings are listed and defined, and a sample program listing with a complete list of symbols and references is provided.
Date: January 18, 1979
Creator: Crawford, R.W.
Partner: UNT Libraries Government Documents Department

Empirical technique to measure x-ray production and detection efficiencies in the analytical electron microscope

Description: In the present work, a technique is proposed to experimentally measure the effective x-ray production and detection efficiency in pure element standards. This technique supplements and in some cases is preferable to the multi-element standard technique. Measurements of effective x-ray production and detection efficiencies are expected to be preferable to the standardless technique in cases where pure element samples can be prepared since the most uncertain parameters in the standardless technique are measured in the proposed technique.
Date: January 1, 1985
Creator: King, W.E.
Partner: UNT Libraries Government Documents Department

Nanosecond fluorescence spectroscopy

Description: This article is a summary of a short course lecture given in conjunction with the 1984 Nuclear Science Symposium. Measuring systems for nanosecond fluorescence spectroscopy using single-photon counting techniques are presented. These involve systems based on relaxation-type spark gap light pulser and synchronously pumped mode-locked dye lasers. Furthermore, typical characteristics and optimization of operating conditions of the critical components responsible for the system time resolution are discussed. A short comparison of the most important deconvolution methods for numerical analysis of experimental data is given particularly with respect to the signal-to-noise ratio of the fluorescence signal. 22 refs., 8 figs.
Date: March 1, 1985
Creator: Leskovar, B.
Partner: UNT Libraries Government Documents Department

Automated atomic absorption spectrophotometer, utilizing a programmable desk calculator

Description: A commercial, double-beam atomic absorption spectrophotometer has been interfaced with a sample changer and a Hewlett-Packard 9810A calculator to yield a completely automated analysis system. The interface electronics can be easily constructed and should be adaptable to any double-beam atomic absorption instrument. The calculator is easily programmed and can be used for general laboratory purposes when not operating the instrument. The automated system has been shown to perform very satisfactorily when operated unattended to analyze a large number of samples. Performance statistics agree well with a manually operated instrument.
Date: March 28, 1977
Creator: Futrell, T. L. & Morrow, R. W.
Partner: UNT Libraries Government Documents Department

Finite Element Analysis of the Distortion of a Crystal Monochromator From Synchrotron Radiation Thermal Loading

Description: The first crystal of the Brown-Hower x-ray monochromator of the LBL-EXXON 54 pole wiggler beamline at Stanford Synchrotron Radiation Laboratory (SSRL) is subjected to intense synchrotron radiation. To provide an accurate thermal/structural analysis of the existing monochromator design, a finite element analysis (FEA) was performed. A very high and extremely localized heat flux is incident on the Si (220) crystal. The crystal, which possesses pronouncedly temperature-dependent orthotropic properties, in combination with the localized heat load, make the analysis ideally suited for finite element techniques. Characterization of the incident synchrotron radiation is discussed, followed by a review of the techniques employed in modeling the monochromator and its thermal/structural boundary conditions. The results of the finite element analysis, three-dimensional temperature distributions, surface displacements and slopes, and stresses, in the area of interest, are presented. Lastly, the effects these results have on monochromator output flux and resolution are examined.
Date: October 1985
Creator: Edwards, W. R.; Hoyer, E. H. & Thompson, A. C.
Partner: UNT Libraries Government Documents Department

Helium-to-neon modification for a DuPont 120SSA or 24-120 leak detector

Description: When helium leak detecting is hindered by a system or atmosphere saturated with helium, leak checking can be continued by modifying the DuPont 120SSA/24-120 Mass Spectrometer Leak Detector to detect neon. Although DuPont markets a three gas leak detector (helium, neon and argon), the DuPont 120SSA/24-120 is convertible to neon by simply changing the magnet and retuning for neon peak. The sensitivity is 2 x 10/sup -9/ Atm/cc/sec/division neon. If an increase in sensitivity is desired, throttle diffusion pump with valve or install choke. Modification procedures and tuning procedures are described. (WHK)
Date: August 26, 1982
Creator: Juravic, F.
Partner: UNT Libraries Government Documents Department

Computer programs in BASIC language for atomic absorption flame spectroscopy. Part 2. Documentation. [SEMIAUTOMATIC, RANDOM, and BRACKET codes]

Description: There are three computer programs, written in the BASIC language, used for taking data from an atomic absorption spectrophotometer operating in the flame mode. The programs are divided into logical sections, and these have been flow-charted. The general features, the structure, the order of subroutines and functions, and the storage of data are discussed. In addition, variables are listed and defined, and a complete listing of each program with a symbol occurrence table is provided.
Date: October 28, 1977
Creator: Boyle, W.G. Jr.
Partner: UNT Libraries Government Documents Department

Laser-based secondary neutral mass spectroscopy: Useful yield and sensitivity

Description: A variety of problems exist in order to optimally apply resonance ionization spectroscopy (RIS) to the detection of sputtered neutral atoms, however. Several of these problems and their solutions are examined in this paper. First, the possible useful yields obtainable and the dependence of useful yield on various laser parameters for this type of sputtered neutral mass spectrometer (SNMS) are considered. Second, the choice of a mass spectrometer and its effect on the instrumental useful yield is explored in light of the unique ionization region for laser based SNMS. Finally a brief description of noise sources and their effect on the instrumental sensitivity is discussed. 33 refs., 12 figs.
Date: January 1, 1986
Creator: Young, C.E.; Pellin, M.J.; Calaway, W.F.; Joergensen, B.; Schweitzer, E.L. & Gruen, D.M.
Partner: UNT Libraries Government Documents Department

Filament power regulator for thermal ionization mass spectrometry

Description: A device has been developed that will control the filament temperature in a thermal ionization mass spectrometer. The arrangement is superior to past methods to control this critical parameter. The operating principle lies in the feature of filament power control as contrasted with the formerly used voltage or current controls. Reproducibility and stability of ion beams showed great improvement. The mass spectrometer was developed to analyze for parts-per-billion concentrations of uranium in water samples.
Date: September 15, 1977
Creator: Rogers, E. R. & Ferguson, J. R.
Partner: UNT Libraries Government Documents Department

Instruction manual for a microwave ammonia monitor

Description: The microwave ammonia monitor is a self contained (the vacuum pump is external) microwave rotational spectrometer that selectively detects and monitors ammonia vapor in air. A solid-state oscillator is used as the microwave source and a microwave cavity made from waveguide provides a chamber for the sample analysis. The air sample is continuously flowed through the waveguide cavity so that changes in the trace concentration of ammonia in air can be determined. The principle of operation of the microwave ammonia monitor is based on the absorption of microwave radiation by a vibration-rotation quantum transition of the ammonia molecule. Ammonia absorbs microwave radiation in a very narrow frequency range with its peak at 23,870.18 MHz. The microwave source is electronically controlled to oscillate only at this frequency and to provide a very stable output power. Thus, even a very small amount of microwave power that is absorbed by the ammonia gas is detectable and no other gas in the air sample is known to absorb any microwave radiation within the frequency output band of the oscillator. The specifications, operation, and maintenance procedures are described. Also a parts list and engineering drawings are included. (WHK)
Date: June 13, 1977
Creator: Hrubesh, Lawrence W.
Partner: UNT Libraries Government Documents Department

Thermal-emission mass spectrometer for rapid and accurate determination of uranium isotopes

Description: A 60-degree (..pi../3-radian) magnetic-sector, 6-inch (152.4-mm) mass spectrometer has been designed and built for uranium isotopic analyses. The instrument uses a Nier-type geometry and has several improvements, both optically and electrically, which make it rapid and precise. Instrument control is good and the analytical results for uranium isotopes are excellent.
Date: August 31, 1978
Creator: McBryde, W.T.; Rogers, E.R. & Ferguson, J.R.
Partner: UNT Libraries Government Documents Department