scholarly journals Field-Strength Depression of Emitters Dispersed from a Point Source into a Cylindrical Volume

2021 ◽  
Vol 09 (04) ◽  
pp. 545-555
Author(s):  
Palmer G. Steward
Keyword(s):  
Field Strength ◽  
Point Source ◽  
Cylindrical Volume

FOCUSING OF CHARGED PARTICLES IN A CYLINDRICALLY SYMMETRIC MAGNETIC FIELD PROPORTIONAL TO r−1

1963 ◽  
Vol 41 (3) ◽  
pp. 496-532 ◽  
Author(s):  
G. E. Lee-Whiting
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Point Source ◽  
Charged Particles ◽  
Source Area ◽  
Cylindrically Symmetric ◽  
Finite Source ◽  
Flat Type ◽  
Wide Range ◽  
Finite Aperture

The aberrations associated with skew trajectories lying near the midplane of a "flat"-type β spectrometer with a magnetic field falling off as r−1 have been surveyed over wide ranges of values of the field strength at the source and of the angle of emission; Lafoucrière (1950) showed that such a field possesses a perfect focus for midplanar orbits. A field strength has been found for which the aberrations corresponding to finite aperture are exceedingly small; with a point source it would be possible to get transmissions of 2.3% and 6.0% at resolutions of 0.01% and 0.1% respectively. The defocusing resulting from finite source-height has been studied for this particular value of the field strength and has been found to be large; the resulting permissible source-area is so small that the luminosity of the instrument is inferior to that of a π√2 spectrometer.Methods of producing fields varying as r−1 over a wide range of r have been investigated; both iron pole-pieces and iron-free coils have been considered.

Height and Angle Characteristics of Point Source Transmitting Power of Wireless Avionics Intra-Communication Systems Based on FDTD Analysis

2021 ◽  
Vol 35 (11) ◽  
pp. 1274-1275
Author(s):  
Shunichi Futatsumori ◽  
Kazuyuki Morioka ◽  
Takashi Hikage ◽  
Tetsuya Sekiguchi ◽  
Manabu Yamamoto ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Point Source ◽  
Communication Systems ◽  
Large Scale ◽  
Three Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Radiated Power

The equivalent isotopically radiated power (EIRP) of a wireless avionics intra-communication (WAIC) system is limited to 6 dBm/MHz at the geometrical center of the aircraft, to avoid interference with aircraft radio altimeters, which are operated at the same frequency band between 4,200–4,400 MHz. In this paper, the height and angle characteristics of the point source EIRP of a WAIC system are analyzed based on the large scale FDTD analysis. Firstly, the strength of the electric field (E-field) around the three-dimensional model of Airbus A320-200 is analyzed. Then, the point source EIRP is calculated based on the analyzed E-field strength. Finally, the height and angle characteristics are analyzed to estimate the electromagnetic field characteristics of the aircraft.

scholarly journals Improvement of the Point Spread Function by Collimators’ New Configuration in Nuclear Medicine

2021 ◽  
Author(s):  
Mansour Ashoor ◽  
Abdollah Khorshidi
Keyword(s):  
Nuclear Medicine ◽  
Point Source ◽  
Point Spread Function ◽  
Parametric Method ◽  
Delta Function ◽  
Mcnpx Code ◽  
Point Spread ◽  
Spread Function ◽  
Cylindrical Volume ◽  
Theoretical Results

Abstract Objective: The collimators in which the various geometrical configurations have been suggested to optimize the sensitivity and resolution have a key role in acquiring the qualified images in nuclear medicine towards a better recognition of some diseases. Methods: In this study, a new configuration as a geometrical combination of the conical, cylindrical and spherical (CCS) volumes for parallel hole collimators which is assessed by using the volumetric-parametric method has been introduced to improve point spread function (PSF) being the collimators response on the radioactive point source. It has been simulated by the MCNPX code at the various energies values of the point source along with the traditional collimator in which included the cylindrical volume only. Results: The PSF will transmogrify from a delta function to a distribution which can correlate with a Gaussian distribution, while the scattered gamma rays were increased. The simulation results have indicated that the PSF in the CCS configuration is narrower than that of the cylindrical one at all the energies, leading the improvement of the resolution. Also, the theoretical results are agreement with the simulated ones. The more the energy value of the source, the more broaden the PSF will be due the more penetration strength. The narrower the PSF, the better the qualified image will be. Conclusion: This method may be employed to determine the accurate attenuation coefficient of absorbers as well.

On the Configuration of the Magnetic Field of β CrB

1976 ◽  
Vol 32 ◽  
pp. 613-622
Author(s):  
I.A. Aslanov ◽  
Yu.S. Rustamov
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Radial Velocity ◽  
Magnetic Field Strength ◽  
Complex Shape ◽  
Rotation Period ◽  
Field Variation ◽  
Magnetic Field Variation ◽  
Secular Variations ◽  
The Magnetic Field

SummaryMeasurements of the radial velocities and magnetic field strength of β CrB were carried out. It is shown that there is a variability with the rotation period different for various elements. The curve of the magnetic field variation measured from lines of 5 different elements: FeI, CrI, CrII, TiII, ScII and CaI has a complex shape specific for each element. This may be due to the presence of magnetic spots on the stellar surface. A comparison with the radial velocity curves suggests the presence of a least 4 spots of Ti and Cr coinciding with magnetic spots. A change of the magnetic field with optical depth is shown. The curve of the Heffvariation with the rotation period is given. A possibility of secular variations of the magnetic field is shown.

Improvements in the electron probe forming capabilities and x-ray hole counts in the Philips TEM

1983 ◽  
Vol 41 ◽  
pp. 376-377
Author(s):  
Richard L. McConville
Keyword(s):  
Field Strength ◽  
Electron Probe ◽  
Spherical Aberration ◽  
Focal Length ◽  
Objective Lens ◽  
Parallel Beam ◽  
Tilt Axis ◽  
X Ray ◽  
Small Probe ◽  
Specimen Height

A second generation twin lens has been developed. This symmetrical lens with a wider bore, yet superior values of chromatic and spherical aberration for a given focal length, retains both eucentric ± 60° tilt movement and 20°x ray detector take-off angle at 90° to the tilt axis. Adjust able tilt axis height, as well as specimen height, now ensures almost invariant objective lens strengths for both TEM (parallel beam conditions) and STEM or nano probe (focused small probe) modes.These modes are selected through use of an auxiliary lens situ ated above the objective. When this lens is on the specimen is illuminated with a parallel beam of electrons, and when it is off the specimen is illuminated with a focused probe of dimensions governed by the excitation of the condenser 1 lens. Thus TEM/STEM operation is controlled by a lens which is independent of the objective lens field strength.

A photoelectron microscope study of surfaces

1989 ◽  
Vol 47 ◽  
pp. 10-11
Author(s):  
W. Engel ◽  
M. Kordesch ◽  
A. M. Bradshaw ◽  
E. Zeitler
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Field Strength ◽  
Uv Light ◽  
Physical Property ◽  
Photon Flux ◽  
Mercury Lamp ◽  
Object Surface ◽  
The Sixties ◽  
Physical Features

Photoelectron microscopy is as old as electron microscopy itself. Electrons liberated from the object surface by photons are utilized to form an image that is a map of the object's emissivity. This physical property is a function of many parameters, some depending on the physical features of the objects and others on the conditions of the instrument rendering the image.The electron-optical situation is tricky, since the lateral resolution increases with the electric field strength at the object's surface. This, in turn, leads to small distances between the electrodes, restricting the photon flux that should be high for the sake of resolution.The electron-optical development came to fruition in the sixties. Figure 1a shows a typical photoelectron image of a polycrystalline tantalum sample irradiated by the UV light of a high-pressure mercury lamp.

XRMF applications of a monolithic, polycapillary, focusing x-ray optic

1996 ◽  
Vol 54 ◽  
pp. 240-241
Author(s):  
D. A. Carpenter ◽  
Ning Gao ◽  
G. J. Havrilla
Keyword(s):  
Trace Elements ◽  
Point Source ◽  
Focal Spot ◽  
Fluorescence Analysis ◽  
X Rays ◽  
Focal Distance ◽  
Spot Diameter ◽  
X Ray ◽  
Focal Spot Diameter

A monolithic, polycapillary, x-ray optic was adapted to a laboratory-based x-ray microprobe to evaluate the potential of the optic for x-ray micro fluorescence analysis. The polycapillary was capable of collecting x-rays over a 6 degree angle from a point source and focusing them to a spot approximately 40 µm diameter. The high intensities expected from this capillary should be useful for determining and mapping minor to trace elements in materials. Fig. 1 shows a sketch of the capillary with important dimensions.The microprobe had previously been used with straight and with tapered monocapillaries. Alignment of the monocapillaries with the focal spot was accomplished by electromagnetically scanning the focal spot over the beveled anode. With the polycapillary it was also necessary to manually adjust the distance between the focal spot and the polycapillary.The focal distance and focal spot diameter of the polycapillary were determined from a series of edge scans.

Performance Evaluation of a Novel Type of Low-Energy Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 354-355
Author(s):  
Bertholdand Senftinger ◽  
Helmut Liebl
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Field Strength ◽  
Numerical Aperture ◽  
Low Energy ◽  
Energy Electron ◽  
High Resolution Imaging ◽  
Lens System ◽  
Resolution Imaging ◽  
Low Energy Electron

During the last few years the investigation of clean and adsorbate-covered solid surfaces as well as thin-film growth and molecular dynamics have given rise to a constant demand for high-resolution imaging microscopy with reflected and diffracted low energy electrons as well as photo-electrons. A recent successful implementation of a UHV low-energy electron microscope by Bauer and Telieps encouraged us to construct such a low energy electron microscope (LEEM) for high-resolution imaging incorporating several novel design features, which is described more detailed elsewhere.The constraint of high field strength at the surface required to keep the aberrations caused by the accelerating field small and high UV photon intensity to get an improved signal-to-noise ratio for photoemission led to the design of a tetrode emission lens system capable of also focusing the UV light at the surface through an integrated Schwarzschild-type objective. Fig. 1 shows an axial section of the emission lens in the LEEM with sample (28) and part of the sample holder (29). The integrated mirror objective (50a, 50b) is used for visual in situ microscopic observation of the sample as well as for UV illumination. The electron optical components and the sample with accelerating field followed by an einzel lens form a tetrode system. In order to keep the field strength high, the sample is separated from the first element of the einzel lens by only 1.6 mm. With a numerical aperture of 0.5 for the Schwarzschild objective the orifice in the first element of the einzel lens has to be about 3.0 mm in diameter. Considering the much smaller distance to the sample one can expect intense distortions of the accelerating field in front of the sample. Because the achievable lateral resolution depends mainly on the quality of the first imaging step, careful investigation of the aberrations caused by the emission lens system had to be done in order to avoid sacrificing high lateral resolution for larger numerical aperture.

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