A COMPTON-ELECTRON γ-SPECTROMETER WITH TWO-DIRECTIONAL FOCUSING

1960 ◽  
Vol 38 (6) ◽  
pp. 720-750 ◽  
Author(s):  
G. E. Lee-Whiting
Keyword(s):  
Magnetic Field ◽  
Line Width ◽  
Cylindrical Symmetry ◽  
Maximum Efficiency ◽  
Electron Spectrometer ◽  
Γ Rays ◽  
Γ Ray ◽  
Compton Electron ◽  
Γ Spectrometer ◽  
The Magnetic Field

Improvements in the design of one type of Compton-electron spectrometer for γ-rays are proposed. The design requires a magnetic field of cylindrical symmetry and of slow radial variation, a simply curved radiator, and a system of apertures. Electrons are accepted only if they are ejected from the radiator with small components of momentum in two orthogonal directions perpendicular to the incident γ-ray. Since the magnetic field can also be used to measure the momentum of the selected electrons, the instrument can function as a γ-ray spectrometer. Higher-order aberrations are discussed, and a method of calculating the values of the various spectrometer parameters corresponding to maximum efficiency is given. Calculations of the intrinsic line-width, caused by the motion of the electron within the atom before collision with the photon, are carried out.

THE LOW-TEMPERATURE ORDERED STATE OF CERIUM MAGNESIUM NITRATE AND ITS INFLUENCE ON NUCLEAR ORIENTATION

1964 ◽  
Vol 42 (8) ◽  
pp. 1469-1480 ◽  
Author(s):  
J. M. Daniels ◽  
J. Felsteiner
Keyword(s):  
Magnetic Field ◽  
Nuclear Orientation ◽  
Dipole Interaction ◽  
Magnesium Nitrate ◽  
Divalent Ions ◽  
Antiferromagnetic Ordering ◽  
Γ Rays ◽  
Γ Ray ◽  
The Magnetic Field ◽  
Ordered State

The method of Luttinger and Tisza for minimizing the dipole–dipole interaction energy is applied to cerium magnesium nitrate, and an antiferromagnetic ordering of the cerium spins at 0 °K is found. Using this configuration, the magnetic field at the divalent ions is calculated. Next, the anisotropy of γ rays from Co60 aligned in this salt is calculated for temperatures below 0.003 °K. Qualitative agreement is found between these calculations and measurements of γ-ray anisotropy reported in the literature.

scholarly journals A lower limit to the magnetic field in the Crab Nebula from cosmic γ-ray experiments at 1011 eV

1970 ◽  
Vol 37 ◽  
pp. 250-256
Author(s):  
G. G. Fazio ◽  
H. F. Helmken ◽  
G. H. Rieke ◽  
T. C. Weekes
Keyword(s):  
Magnetic Field ◽  
Lower Limit ◽  
Crab Nebula ◽  
High Energy ◽  
Secondary Products ◽  
High Energy Electrons ◽  
Γ Rays ◽  
Γ Ray ◽  
The Crab Nebula ◽  
The Magnetic Field

The 10-m optical reflector at Mt. Hopkins, Arizona, has been used to search for cosmic γ-Rays by the detection of atmospheric Čerenkov radiation from energetic particle showers. Approximately 100 drift scans of the Crab Nebula during 1968–69 have yielded no positive evidence of a γ-Ray flux. The upper limit to the flux at 1.7 × 1011 eV is 2.0 × 10−10 photons/cm2 sec. Assuming γ-Rays of this energy are produced by Compton scattering, a lower limit on the average magnetic field in the Crab Nebula is 1.5 × 10−4 gauss. This experiment also verifies previous evidence that the high-energy electrons in the Crab Nebula are not the secondary products of high-energy proton interactions but must have been accelerated from lower energies.

THE MEASUREMENT OF ENERGIES AND INTENSITIES OF γ-RAYS WITH A PAIR SPECTROMETER

1953 ◽  
Vol 31 (4) ◽  
pp. 537-576 ◽  
Author(s):  
B. B. Kinsey ◽  
G. A. Bartholomew
Keyword(s):  
Magnetic Field ◽  
Good Method ◽  
Counting Efficiency ◽  
Coincidence Spectrum ◽  
Slit Width ◽  
Experimental Point ◽  
Γ Rays ◽  
Γ Ray ◽  
The Magnetic Field ◽  
Good Agreement

The performance of a pair spectrometer of the Walker and McDaniel type is discussed from both a theoretical and an experimental point of view. It is shown that the energy of the γ-ray may be measured to a first approximation by the product of the distance between the inner edges of the slits which define the coincidence counters and the highest value of the magnetic field at which coincidences are found. A more accurate value of the energy of the γ-ray may be obtained by adding a small correction, called the "toe" correction, to the result so obtained. The magnitude of this correction is dependent on the γ-ray energy and on the width of the slits and is obtained from calculations of the shape of the coincidence peak based on the Bethe–Heitler formula. The correction depends very little on the length of the slits or on the thickness of the radiator. The relation between the calculated correction and the slit width has been examined experimentally. It is shown that the ultimate accuracy in energy measurement depends on the homogeneity of the magnetic field and on the error involved in the calculated toe correction. The latter error can be minimized by using very narrow slits and may be eliminated by plotting the value of magnetic field at the upper limit of the coincidence spectrum against the slit width and extrapolating the curve so obtained to zero slit width. The uncertainty in the magnetic field of the present instrument introduces a possible systematic error of about 0.05%. Measured values of the energies of a number of neutron capture γ-rays are compared with the values derived from the energy balance in (d, p) reactions. The results are in good agreement (within 0.1%).The relative counting efficiency as a function of energy is calculated theoretically and found to be in good agreement with experiment from 2.75 to 7.4 Mev. Above 7.4 Mev. no good method of checking the theoretical efficiency has been found. The absolute value of the counting efficiency at 2.75 and 7.38 Mev. has been measured by an ionization chamber method and is found to be in rough agreement with theoretical estimates.

scholarly journals Non-damping oscillations at flaring loops

2018 ◽  
Vol 617 ◽  
pp. A86 ◽  
Author(s):  
D. Li ◽  
D. Yuan ◽  
Y. N. Su ◽  
Q. M. Zhang ◽  
W. Su ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Line Width ◽  
Line Emission ◽  
Flux Rope ◽  
Doppler Velocity ◽  
Narrow Slit ◽  
Plasma Properties ◽  
Spectral Window ◽  
Peak Intensity ◽  
The Magnetic Field

Context. Quasi-periodic oscillations are usually detected as spatial displacements of coronal loops in imaging observations or as periodic shifts of line properties (i.e., Doppler velocity, line width and intensity) in spectroscopic observations. They are often applied for remote diagnostics of magnetic fields and plasma properties on the Sun. Aims. We combine the imaging and spectroscopic measurements of available space missions, and investigate the properties of non-damping oscillations at flaring loops. Methods. We used the Interface Region Imaging Spectrograph (IRIS) to measure the spectrum over a narrow slit. The double-component Gaussian fitting method was used to extract the line profile of Fe XXI 1354.08 Å at the “O I” spectral window. The quasi-periodicity of loop oscillations were identified in the Fourier and wavelet spectra. Results. A periodicity at about 40 s is detected in the line properties of Fe XXI 1354.08 Å, hard X-ray emissions in GOES 1−8 Å derivative, and Fermi 26−50 keV. The Doppler velocity and line width oscillate in phase, while a phase shift of about π/2 is detected between the Doppler velocity and peak intensity. The amplitudes of Doppler velocity and line width oscillation are about 2.2 km s−1 and 1.9 km s−1, respectively, while peak intensity oscillates with amplitude at about 3.6% of the background emission. Meanwhile, a quasi-period of about 155 s is identified in the Doppler velocity and peak intensity of the Fe XXI 1354.08 Å line emission, and AIA 131 Å intensity. Conclusions. The oscillations at about 40 s are not damped significantly during the observation; this might be linked to the global kink modes of flaring loops. The periodicity at about 155 s is most likely a signature of recurring downflows after chromospheric evaporation along flaring loops. The magnetic field strengths of the flaring loops are estimated to be about 120−170 G using the magnetohydrodynamic seismology diagnostics, which are consistent with the magnetic field modeling results using the flux rope insertion method.

scholarly journals On the Predictive Power of the Minimum Energy Condition

1993 ◽  
Vol 157 ◽  
pp. 413-414
Author(s):  
Martin Pohl
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Predictive Power ◽  
Spiral Galaxies ◽  
Minimum Energy ◽  
Energy Condition ◽  
Cosmic Ray ◽  
Γ Ray ◽  
Minimum Energy Method ◽  
The Magnetic Field

We reexamine the minimum energy method to determine the magnetic field strength in spiral galaxies from the cosmic ray standpoint of view. It is shown that for example in M51 the estimated field strength is about a factor of 2 lower than obtained with the standard method. As a by-product the corresponding γ-ray flux from the galaxies can be calculated, which will allow further improvement of the method provided reliable γ-ray spectra are at hand.

Optimization of magnetic hat for quartz flexible accelerometer

Sensor Review ◽  
2016 ◽  
Vol 36 (1) ◽  
pp. 71-76 ◽  
Author(s):  
Cuo Wang ◽  
Xingfei Li ◽  
Ke Kou ◽  
Chunguo Long
Keyword(s):  
Magnetic Field ◽  
Field Distribution ◽  
Cylindrical Symmetry ◽  
Air Gap ◽  
Magnetic Sensors ◽  
Magnetic Field Distribution ◽  
Navigation Systems ◽  
Pole Piece ◽  
Content Type ◽  
The Magnetic Field

Purpose – This study aims to ameliorate the strength and uniformity of the magnetic field in the air-gap of quartz flexible accelerometers. Quartz flexible accelerometers (QFAs), a type of magneto-electric inertial sensors, have wide applications in inertial navigation systems, and their precision, linearity and stability performance are largely determined by the magnetic field in operation air-gap. To enhance the strength and uniformity of the magnetic field in the air-gap, a magnetic hat structure has been proposed to replace the traditional magnetic pole piece which tends to produce stratiform magnetic field distribution. Design/methodology/approach – Three-dimensional analysis in ANSYS workbench helps to exhibit magnetic field distribution for the structures with a pole piece and a magnetic hat, and under the hypothesis of cylindrical symmetry, two-dimensional finite element optimization by ANSYS APDL gives an optimal set of dimensions of the magnetic hat. Findings – Three structures of the QFA with a pole piece, a non-optimized magnetic hat and an optimized magnetic hat are compared by the simulation in ANSYS Maxwell and experiments measuring the electromagnetic rebalance force. The results show that the optimized hat can supply stronger and more uniform magnetic field, which is reflected by larger and more linear rebalance force. Originality/value – To the authors ' knowledge, the magnetic hat and its dimension optimization have rarely been reported, and they can find significant applications in designing QFAs or other similar magnetic sensors.

Considerations of the effect of space-charge in the magnetron

1940 ◽  
Vol 36 (1) ◽  
pp. 94-100 ◽  
Author(s):  
E. B. Moullin
Keyword(s):  
Magnetic Field ◽  
Space Charge ◽  
Cylindrical Symmetry ◽  
Potential Difference ◽  
Anode Current ◽  
Pronounced Decrease ◽  
Field Parallel ◽  
Image Position ◽  
The Magnetic Field

When a diode thermionic tube, having cylindrical symmetry, is placed in a magnetic field parallel to its axis it is commonly called a magnetron. If there is a given potential difference between the anode and cathode of the tube, and if the magnetic field is steadily increased, a sharp and pronounced decrease of anode current occurs when the field reaches a certain value. It is easy to show that, if electrons leave without velocity from a cathode of radius b, they will just graze a concentric anode of radius a at potential V when the magnetic field H has the value given by

The magnetic field at chromium nuclei in iron and nickel

1976 ◽  
Vol 54 (8) ◽  
pp. 827-829 ◽  
Author(s):  
S. A. Wender ◽  
L. Keszthelyi ◽  
J. A. Cameron
Keyword(s):  
Magnetic Field ◽  
Angular Distribution ◽  
Magnetic Fields ◽  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Γ Rays ◽  
The Magnetic Field

The integral rotation of the angular distribution of γ rays from the 749 keV level of 51 Cr excited by the (α,n) reaction in Ti5Fe95 and Ti5Ni95 targets has been used to measure the hyperfine magnetic fields at Cr nuclei in these alloys at liquid nitrogen temperature. The values are[Formula: see text]

CYLINDRICAL TM-MODES IN A HOMOGENEOUS SELF-FOCUSING DIELECTRIC

1996 ◽  
Vol 06 (07) ◽  
pp. 977-1008 ◽  
Author(s):  
C.A. STUART
Keyword(s):  
Magnetic Field ◽  
Variational Principle ◽  
Dielectric Response ◽  
Extreme Values ◽  
Homogeneous Medium ◽  
Cylindrical Symmetry ◽  
Trapped Modes ◽  
Self Focusing ◽  
Light Beams ◽  
The Magnetic Field

This paper deals with the mathematical analysis of self-trapped light beams in a homogeneous medium which has a self-focusing dielectric response. We consider modes where the electromagnetic fields have a cylindrical symmetry and the magnetic field is transverse to the direction of propagation. The main results establish a range of wavelengths for which such guided modes exist. The behavior of the power of the beam as the wavelength approaches its extreme values is also determined. The existence of self-trapped modes is established using a variational principle. Bounds on the wavelength and the power are obtained directly from the associated quasilinear eigenvalue problem.

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