ANGULAR DISTRIBUTIONS AND ENERGY SPECTRA OF ELECTRONS ASSOCIATED WITH AURORAL EVENTS

1964 ◽  
Vol 42 (11) ◽  
pp. 2048-2062 ◽  
Author(s):  
I. B. McDiarmid ◽  
E. E. Budzinski
Keyword(s):  
Angular Distributions ◽  
Recombination Coefficient ◽  
Particle Detectors ◽  
Black Brant ◽  
Intensity Measurements ◽  
Intensity Changes ◽  
D Region ◽  
Electron Intensity ◽  
Particle Intensity ◽  
Probe Measurements

A number of Black Brant II rockets containing various charged-particle detectors have been fired during 1963 and 1964 from Fort Churchill, Manitoba. Most of the firings took place at times of auroral events and the rocket instrumentation was designed to study the particles associated with these events.Pitch-angle distributions have been observed for electrons with energies greater than 40 keV, which show varying degrees of isotropy in the pitch-angle range 0° to 90°. In no case has a distribution been observed in which the intensity increased towards small angles. In some cases electron-intensity changes appear to be correlated with changes in spectrum and angular distribution, while in other cases changes in these quantities do not appear to be related.The particle intensity measurements are used along with radio-frequency probe measurements of electron density to infer values for the nighttime recombination coefficient in the D region of the ionosphere.

ROCKET OBSERVATIONS OF ELECTRON PITCH-ANGLE DISTRIBUTIONS DURING AURORAL SUBSTORMS

1967 ◽  
Vol 45 (5) ◽  
pp. 1755-1769 ◽  
Author(s):  
I. B. McDiarmid ◽  
E. E. Budzinski ◽  
B. A. Whalen ◽  
N. Sckopke
Keyword(s):  
Geomagnetic Field ◽  
Pitch Angle ◽  
Angular Distributions ◽  
Intensity Increase ◽  
Ionospheric Current ◽  
Atmospheric Scattering ◽  
Auroral Substorms ◽  
Electron Intensity ◽  
Upward Moving ◽  
Particle Intensity

Electron angular distributions obtained from three rocket flights during auroral substorms are described. Pitch-angle distributions of the incident electrons vary from isotropic to strongly peaked at pitch angles near 90°. Isotropic distributions are sometimes maintained for times at least of the order of minutes with very little change in intensity. When an anisotropic distribution persists for some time, the particle intensity is usually observed to decay.Following an intensity increase the angular distribution generally becomes more isotropic. The degree of isotropy attained following an intensity increase does not appear to depend on the magnitude of the increase but rather on the degree of isotropy before the increase.The intensity of upward moving electrons (pitch angles 90–180°) can in most cases be accounted for by atmospheric scattering and mirroring in the undisturbed geomagnetic field. A few cases are observed in which the electron intensity in the pitch-angle range 90–180° is probably larger than can be accounted for by normal scattering and mirroring. The effect of an ionospheric current on the intensity of upward moving electrons is considered.

Thickness and composition determinations from T.E.M. specimens using both x-ray and backscattered electron data

1984 ◽  
Vol 42 ◽  
pp. 576-577
Author(s):  
M.D. Ball ◽  
H. Lagace ◽  
M.C. Thornton
Keyword(s):  
Electron Microscope ◽  
Atomic Number ◽  
Transmission Electron Microscope ◽  
Convenient Method ◽  
Flow Chart ◽  
X Ray ◽  
Intensity Measurements ◽  
Transmission Electron ◽  
Electron Intensity ◽  
Backscattered Electron

The backscattered electron coefficient η for transmission electron microscope specimens depends on both the atomic number Z and the thickness t. Hence for specimens of known atomic number, the thickness can be determined from backscattered electron coefficient measurements. This work describes a simple and convenient method of estimating the thickness and the corrected composition of areas of uncertain atomic number by combining x-ray microanalysis and backscattered electron intensity measurements.The method is best described in terms of the flow chart shown In Figure 1. Having selected a feature of interest, x-ray microanalysis data is recorded and used to estimate the composition. At this stage thickness corrections for absorption and fluorescence are not performed.

EFFECT OF α-PARTICLE ENERGIES ON CR-39 LINE-SHAPED PARAMETERS USING POSITRON ANNIHILATION TECHNIQUE (PAT)

2007 ◽  
Vol 21 (22) ◽  
pp. 3851-3858 ◽  
Author(s):  
M. A. ABDEL-RAHMAN ◽  
M. ABDEL-RAHMAN ◽  
YAHIA A. LOTFY ◽  
EMAD A. BADAWI ◽  
M. ABO-ELSOUD ◽  
...  
Keyword(s):  
Phase Transition ◽  
Positron Annihilation ◽  
Radiation Effects ◽  
Particle Energy ◽  
X Ray Diffraction ◽  
Particle Detectors ◽  
Valence Electrons ◽  
Type Particle ◽  
Particle Intensity ◽  
Non Destructive

Polyallyl diglycol carbonate "CR-39" is widely used in etched track-type particle detectors. Doppler-broadening positron annihilation (DBPAT) provides direct information about core and valence electrons in CR-39 due to radiation effects. It provides a non-destructive and non-interfering probe having a detecting efficiency. This paper reports the effect of irradiation α-particle intensity emitted from an 241 Am (5.486 MeV) source on the line-shaped S- and W-parameters for the CR-39 samples. The behavior of the line-shaped S- and W-parameters can be related to the different phases. Modification of the CR-39 samples due to irradiation were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The XRD chart reveals a new peak that starts to appear at 2.86 MeV α-particle energy. The appearance of this peak might be related to the phase transition. The phase transition in the CR-39 polycarbonate remains complex.

ROCKET MEASUREMENTS IN PROTON AURORA

1967 ◽  
Vol 45 (10) ◽  
pp. 3247-3255 ◽  
Author(s):  
B. A. Whalen ◽  
I. B. McDiarmid ◽  
E. E. Budzinski
Keyword(s):  
Pitch Angle ◽  
Energy Spectra ◽  
Angular Distributions ◽  
Electron Spectra ◽  
Source Mechanisms ◽  
Electron Intensity ◽  
Proton Precipitation ◽  
Rocket Measurements ◽  
Short Time ◽  
Proton Aurora

Proton and electron intensities, energy spectra, and angular distributions derived from a recent rocket flight launched into a 40-rayleigh Hβ aurora are reported. High-intensity proton precipitation (~0.45 erg cm−2 s−1 for protons with energies above 30 keV) was detected throughout the flight above 100 km, whereas the electron intensity was above the limit of detectability for only a short time. The proton and electron spectra and angular distributions in the 20–60 keV energy range were found to be remarkably similar, with angular distributions being isotropic over the pitch-angle range 0–90°, and with e-folding energies of about 12 keV and 18 keV for protons and electrons respectively. The results are interpreted in terms of current magnetospheric models, and are shown to place certain restrictions on the source mechanisms.

Self-Referencing Intensity Measurements Based on Square-Wave Gated Phase-Modulation Fluorimetry

2003 ◽  
Vol 57 (5) ◽  
pp. 532-537 ◽  
Author(s):  
H. M. Rowe ◽  
Sing Po Chan ◽  
J. N. Demas ◽  
B. A. DeGraff
Keyword(s):  
Phase Modulation ◽  
Excitation Source ◽  
Dual Emission ◽  
Signal Ratio ◽  
Square Wave ◽  
Intensity Measurements ◽  
Digital Integration ◽  
Pyridinedicarboxylic Acid ◽  
Intensity Changes ◽  
Good Agreement

An adaptation of square-wave gated phase-modulation (GPM) fluorimetry allows for self-referenced intensity measurements without the complexity of dual excitation or dual emission wavelengths. This AC technique utilizes square-wave excitation, gated detection, a reference emitter, and a sensor molecule. The theory and experimental data demonstrating the effectiveness and advantages of the adapted GPM scheme are presented. One component must have an extremely short lifetime relative to the other. Both components are affected identically by changes in intensity of the excitation source, but the sensor intensity also depends on the concentration of the analyte. The fluctuations of the excitation source and any optical transmission changes are eliminated by ratioing the sensor emission to the reference emission. As the concentration of the analyte changes, the corresponding sensor intensity changes can be quantified through several schemes including digitization of the signal and digital integration or AC methods. To measure pH, digital methods are used with Na3[Tb(dpa)3] (dpa = 2,6-pyridinedicarboxylic acid) as the long-lived reference molecule and fluorescein as the short-lived sensor molecule. Measurements from the adapted GPM scheme are directly compared to conventional ratiometric measurements. Good agreement between the data collection methods is demonstrated through the apparent pKa. For the adapted GPM measurements, conventional measurements, and a global fit the apparent pKa values agree within less than 2%. A key element of the adapted GPM method is its insensitivity to fluctuations in the source intensity. For a roughly 8-fold change in the excitation intensity, the signal ratio changes by less than 3%.

The Effect of Surface Roughness in Polymers on X-Ray Fluorescence Intensity Measurements

1967 ◽  
Vol 11 ◽  
pp. 177-184
Author(s):  
J. Gianelos ◽  
C. E. Wilkes
Keyword(s):  
Surface Roughness ◽  
Matrix Effects ◽  
Rough Surfaces ◽  
Target Material ◽  
Wire Mesh ◽  
Coarse Mesh ◽  
X Ray ◽  
Intensity Measurements ◽  
Intensity Changes ◽  
Effect Of Surface

AbstractWe sought to determine how seriously surface roughness affects X-ray intensity measurements in polymers. Fourteen elements ranging from lead to silicon were added singly to fourteen batches of trans-1,4-polyisoprene. Smooth pressings of each batch were made, and intensity readings were taken (I0). Reproducibly rough surfaces were made from these by molding a square wire-mesh pattern into them, with the use of Tyler standard sieve screens. The amount of roughness was controlled by using screens of very fine to very coarse mesh. We studied the change in the X-ray intensity of the rough surfaces versus the smooth [(I/I0) × 100] with respect to: (1) the degree of roughness, (2) concentration of the added element, (3) emitted wavelength of the added element, (4) X-ray tube target material, and (5) correction for matrix effects on the intensity. We found that, at wavelengths emitted below 1 Å, intensity differences are small, regardless of which factors were varied. At wavelengths emitted above 1 Å, however, we found large differences. The intensity changes are highly dependent on roughness. Also, they become greater at the longer emitted wavelengths and with increasing concentration of added elements. Beginning with Ti Kα, losses are much higher with the use of chromium primary radiation than with tungsten. A technique of milling polyethylene into polymers with rough surfaces to provide a smooth surface is discussed.

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