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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

The impact of gas-surface reactions on mass spectrometric measurements of atomic nitrogen

The paper presents a simplified model of the ion source chemistry, explains several details of the data reduction method used in obtaining atomic-nitrogen (N) densities from OSS data, and discusses implications of gas-surface reactions for the design of future satellite-borne mass spectrometers. Because of various surface reactions, N appears in three different forms in the ion source, as N, NO, and NO2. Considering the rather small spin modulation of NO and NO2 in the semi-open ionization chamber used in the OSS instrument, it is not surprising that these reaction products have not been previously identified in closed source instruments as a measure of the presence of atomic nitrogen. Warmup and/or outgassing of the ion source are shown to drastically reduce the NO2 concentration, thereby making possible reliable measurement of ambient N densities.

Engebretson, M. J.↗
NASA NTRS1979

Photoabsorption cross sections of CH3F, CHF3, CH3Cl, and CF2Cl2 from 175 to 760 A

The study of fluorinated and chlorinated hydrocarbons is of great interest because of their suspected effect on the ozone layer in the atmosphere. Using synchrotron radiation as a continuum background, the present study measures photoelectrically the photoabsorption cross sections of CH3F, CHF3, CH3Cl, and CF2Cl2 in the 175-760 A (70.8-16.3 eV) region, using a double ionization chamber. The absolute absorption cross sections and a tentative interpretation of the observed discrete structures are presented.

Wu, C. Y. R.↗
NASA NTRS1981

Study of sulfur-containing molecules in the EUV region. I - Photoabsorption cross section of SO2

Using synchrotron radiation as a continuum background, the absorption cross sections of SO2 have been measured using a double ionization chamber. The cross sections range from 10 to a maximum value of 56 Mb in the 175-760 A region. A possible window resonance series was observed and tentatively assigned to a Ryberg series converging to the (6a sub 1) to the -1st ion state. From the fluorescence excitation function the vibrational progressions of the SO2(+) ion states have been measured and found in good agreement with those observed from photoelectron spectroscopy. The same correspondence between peaks in the fragment fluorescence excitation function and the photoelectron spectrum suggests that these ion states of SO2 are dissociative in nature.

Wu, C. Y. R.↗
NASA NTRS1981

The UH-nuclei cosmic ray detector on the third High Energy Astronomy Observatory

The third High Energy Astronomy Observatory satellite (HEAO-3) carries a particle telescope for the detection of highly charged cosmic ray nuclei. These nuclei, which have Z equal to or greater than 28, are much rarer than the lower charged nuclei in the cosmic radiation. As a consequence, this particle telescope was required to have a large collecting area as well as an ability to resolve individual elements. This paper describes the telescope, composed of large area parallel plate ionization chambers, multiwire ion chamber hodoscopes and a Cherenkov radiation detector. The resulting telescope has a total geometry factor of 59,000 sq cm sr and is capable of measuring the charges of nuclei in the range Z = 14-120.

Binns, W. R.↗
NASA NTRS1983

Study of sulfur-containing molecules in the EUV region. III Photoexcitation of CS2

Using synchrotron radiation as a continuum background, the absorption cross section of CS2 has been measured using a double ionization chamber. The cross sections range from four to a maximum value of 65 Mb in the 175-760 A region. Two new Rydberg series X and XI have been identified and apparently converge to the D2Pi state of CS2(+) at 16.943 eV.

Wu, C. Y. R.↗
NASA NTRS1982

Development of cosmic ray techniques

It is pointed out that most advances of cosmic-ray physics have been directly related to the development of observational techniques. A review is presented of the history of the evolution of the techniques and equipment for the study of cosmic-ray physics, taking into account the new scientific advances accompanying each new development related to experimental technology. All of the early observations were performed by means of ionization chambers. These chambers had already been in use for a number of years, when they were first applied to the study of cosmic rays in the early years of this century. However, an application to the low-intensity cosmic radiation required special refinements. Attention is given to the design of suitable electrometers, the development of self-recording instruments, the 'tube counter', the development of the coincidence method, a cosmic-ray 'telescope', a magnetic lens for cosmic rays, an arrangement of Geiger-Mueller counters for the demonstration of secondary radiation, cloud chambers, scintillation counters, and air shower experiments.

Rossi, B.↗
NASA NTRS1985

Contributions to the 19th International Cosmic Ray Conference

Studies of heavy nuclei in cosmic radiation were studied in an attempt to determine source abundances for various elements. Much of the data analyzed was supplied by the High Energy Astronomy Observatory 3 (HEAO 3) and employed the use of ionization chambers and Cherenrov counters.

Source record↗
NASA NTRS1985

Sidereal anisotropy of cosmic rays

The data of the ionization chamber in Yakutsk for 1954 to 1984 are analyzed. A false sidereal variation caused by the second spherical harmonic in cosmic ray distribution was found and it has the amplitude 0.020 plus or minus 0.002%. The sidereal anisotropy with a very small amplitude (not more than 0.005%) was observed to exist.

Kuzmin, A. I.↗
NASA NTRS1985

The influences of the galactic cosmic ray on the atmospheric ozone

The relationship between the yearly variations of cosmic ray intensity and ozone in the atmosphere, and the ozone disturbance initiated by the Forbush decrease of 1965-1976 is analyzed. The data on cosmic ray intensity were selected from the records of the super neutron monitor at Deep River station and the ionization chamber at Beijing station. Ozone data were taken from Resolute (Canada), Bismark (N. Dakota, USA), Kagoshima (Japan), and Kodaikanal (India). The statistical results show that ozone is prominently modulated and disturbed by the 11 year variation and the Forbush decrease in the galactic cosmic ray.

Ye, Z.↗
NASA NTRS1986

Tandem-Mirror Ion Source

Improved ion source produces beam of ions at any kinetic energy from 1 to 1,000 eV, with little spread in energy or angle. Such ion beams useful in studies of surface properties of materials, surface etching, deposition, and development of plasma-diagnostic instrumentation. Tandemmirror ion source uses electrostatic and magnetic fields to keep electrons in ionization chamber and assure uniform output ion beam having low divergence in energy and angle.

Biddle, A.↗
NASA NTRS1986

Radionuclide measurements by accelerator mass spectrometry at Arizona

Over the past years, Tandem Accelerator Mass Spectrometry (TAMS) has become established as an important method for radionuclide analysis. In the Arizona system the accelerator is operated at a thermal voltage of 1.8MV for C-14 analysis, and 1.6 to 2MV for Be-10. Samples are inserted into a cesium sputter ion source in solid form. Negative ions sputtered from the target are accelerated to about 25kV, and the injection magnet selects ions of a particular mass. Ions of the 3+ charge state, having an energy of about 9MeV are selected by an electrostatic deflector, surviving ions pass through two magnets, where only ions of the desired mass-energy product are selected. The final detector is a combination ionization chamber to measure energy loss (and hence, Z), and a silicon surface-barrier detector which measures residual energy. After counting the trace iosotope for a fixed time, the injected ions are switched to the major isotope used for normalization. These ions are deflected into a Faraday cup after the first high-energy magnet. Repeated measurements of the isotope ratio of both sample and standards results in a measurement of the concentration of the radionuclide. Recent improvements in sample preparation for C-14 make preparation of high-beam current graphite targets directly from CO2 feasible. Except for some measurements of standards and backgrounds for Be-10 measurements to date have been on C-14. Although most results have been in archaeology and quaternary geology, studies have been expanded to include cosmogenic C-14 in meteorites. The data obtained so far tend to confirm the antiquity of Antarctic meteorites from the Allan Hills site. Data on three samples of Yamato meteorites gave terrestrial ages of between about 3 and 22 thousand years.

Jull, A. J. T.↗
NASA NTRS1986

Total absorption and photoionization cross sections of water vapor between 100 and 1000 A

Absolute photoabsorption and photoionization cross sections of water vapor are reported at a large number of discrete wavelengths between 100 and 1000 A with an estimate error of + or - 3 percent in regions free from any discrete structure. The double ionization chamber technique utilized is described. Recent calculations are shown to be in reasonable agreement with the present data.

Haddad, G. N.↗
NASA NTRS1986

Absolute solar flux measurement shortward of 575 A

A rare-gas ionization chamber was used to obtain an accurate measurement of the absolute solar EUV flux in the 50- to 575-A region. The instrument, operating in total and near-total absorption, was flown on a solar-pointing sounding rocket on August 16, 1983. For the day of the flight, the solar activity indices were F sub 10.7 = 132.1 and R sub I = 80, and the integrated solar irradiance at the earth, corrected for atmospheric absorption, was found to be 4.31 + or - 0.31 x 10 to the 10th photons sq cm s. Almost exactly a year earlier (August 10, 1982) the same instrument measured an integrated solar flux of 5.71 + or - 0.42 x 10 to the 10th photons/sq cm s during a time of enhanced solar activity (F sub 10.7 = 209.5 and R sub I = 155).

Ogawa, H. S.↗
NASA NTRS1986

XUV radiometric standards at NBS

The far-UV and XUV detector calibration services at NBS, the properties of the detectors, and the spectrometer calibration facilities at the Synchrotron Ultraviolet Radiation Facility (SURF II) at NBS are described. The method used to calibrate the quantum efficiency of windowless photodiode detectors in the ionization chamber, and the facilities for calibrating photodiodes at various wavelengths are discussed. The cathode and anode of the windowless photodiodes and their operation are examined. Consideration is given to the calculation of spectral irradiance from SURF II; the two stations of the spectrometer facility; the large spectrometer calibration chamber; and sources of error in flux determinations for SURF II.

Ott, W. R.↗
NASA NTRS1996

Analysis of Supercritical-Extracted Chelated Metal Ions From Mixed Organic-Inorganic Samples

Organic and inorganic contaminants of an environmental sample are analyzed by the same GC-MS instrument by adding an oxidizing agent to the sample to oxidize metal or metal compounds to form metal ions. The metal ions are converted to chelate complexes and the chelate complexes are extracted into a supercritical fluid such as CO2. The metal chelate extract after flowing through a restrictor tube is directly injected into the ionization chamber of a mass spectrometer, preferably containing a refractory metal filament such as rhenium to fragment the complex to release metal ions which are detected. This provides a fast, economical method for the analysis of metal contaminants in a sample and can be automated. An organic extract of the sample in conventional or supercritical fluid solvents can be detected in the same mass spectrometer, preferably after separation in a supercritical fluid chromatograph.

Sinha, Mahadeva P.↗
NASA NTRS1994

(abstract) A Miniature, High-Sensitivity, Electron-Tunneling Accelerometer

A prototype low-noise accelerometer has been fabricated with an electron-tunneling transducer. By measuring the tunneling current between an electrode on the proof mass and a feedback-controlled monitor electrode, very small accelerations can be detected with high responsivity. This particular prototype (10x10x1.5 mm) was designed for underwater acoustic measurement from a few hertz to 1 kHz. The measured responsivity below the fundamental device resonance at 100 Hz is roughly 1500 volts per m/s(sup 2) with a measured noise spectral density of 10(sup -6) m/s(sup 2) per root hertz or less between 30 and 300 Hz. The noise floor is controlled primarily by 1/f noise in the tunneling current although the noise floor reaches the theoretical molecular-agitation limit at 100 hertz. The responsivity and directivity of the device were measured in a standard gradient-hydrophone calibrator; the noise floor was determined in a vacuum-ionization chamber assembled from commercial off-the-shelf components; and the detailed dynamics of the proof-mass motion were examined using a heterodyne laser interferometer that was scanned across the surface and synchronously detected with respect to the excitation.

accelerometer electron tunneling acoustic measurem↗
DOE OSTI2024

MEASUREMENT OF THE NEUTRON FLUENCE-RATES IN THE ADVANCED TEST REACTOR

The axial neutron fluence-rate distribution at the Advanced Test Reactor (ATR) is determined using a combination of pure nickel and cobalt-aluminium alloy dosimeter wires. Most irradiation programs at ATR need to know the fast neutron fluence-rate surrounding their experiment to correlate post-irradiation examination results with neutron dose. The activated dosimeter wires, which extend beyond the full fuelled region of the reactor core, are highly radioactive following the full cycle in ATR and must therefore be measured in the ATR canal. The system that is employed for these measurements is mechanical scanning mechanism is used to scan the activated wires across the face of a columnated shield and a NaI detector. This detector is not sufficiently calibrated to provide absolute activity measurements, therefore, the count-rate is recorded and normalized to the highest activity for that wire. Then, an approximately 3-mm long portion of the wire is removed from the highest activity region in the wire. The wires are then transferred, and an absolute activity measurement is made using a calibrated ionization chamber. These measurements are combined with corrections for decay, neutron energy spectrum, burnup, dosimeter composition, reactor power fluctuations, and reactor outages to determine the average axial neutron fluence-rate at various locations within ATR during the cycle.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗