scholarly journals PHOTODIODE BASED ON THE EPITAXIAL PHOSPHIDE GALLIUM WITH INCREASED SENSITIVITY AT A WAVELENGTH OF 254 nm

2020 ◽  
Vol 10 (1) ◽  
pp. 36-39
Author(s):  
Yurii Dobrovolsky ◽  
Volodymyr M. Lipka ◽  
Volodymyr V. Strebezhev ◽  
Yurii O. Sorokatyi ◽  
Mykola O. Sorokatyi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Barrier Layer ◽  
Gallium Phosphide ◽  
Dynamic Range ◽  
Spectral Characteristics ◽  
High Sensitivity ◽  
Ion Etching ◽  
Increased Sensitivity ◽  
20 Nm ◽  
The Magnetic Field

The paper shows the results of the development of a photodiode technology based on gallium phosphide structure n+-n-GaP-Au with high sensitivity. It provides the ion etching of the surface of the gallium phosphide before an application of a leading electrode of gold. The barrier layer of a 20 nm thick gold is applied to the substrate in the magnetic field of GaP. When forming the contact with the reverse side of the indium substrate at 600°C, there occurs the annealing of the gold barrier layer. At the maximum of the spectral characteristics obtained by the photodiode, it has a sensitivity of 0.13 A/W, and at a wavelength of 254 nm – about 0.06 A/W. The dynamic range of the photodiode is not less than 107.

Effect of a static magnetic field on the preparation of MnOOH and Mn3O4 by a hydrothermal process

RSC Advances ◽  
2016 ◽  
Vol 6 (25) ◽  
pp. 21037-21042 ◽  
Author(s):  
L. C. Dong ◽  
Y. B. Zhong ◽  
S. Zhe ◽  
T. Y. Zheng ◽  
H. Wang
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Static Magnetic Field ◽  
Hydrothermal Process ◽  
Single Crystalline ◽  
20 Nm ◽  
The Magnetic Field

In this paper, the shape of the samples was changed by the magnetic field. Single-crystalline nanowires (20 nm in diameter and 1 μm in length) of MnOOH were obtained under zero magnetic fields. However, cubic particles of Mn3O4 were formed when a magnetic field was applied.

scholarly journals Temporal evolution of short-lived penumbral microjets

2020 ◽  
Vol 642 ◽  
pp. A128
Author(s):  
A. L. Siu-Tapia ◽  
L. R. Bellot Rubio ◽  
D. Orozco Suárez ◽  
R. Gafeira
Keyword(s):  
Magnetic Field ◽  
Temporal Evolution ◽  
Spectral Characteristics ◽  
Field Approximation ◽  
Weak Field ◽  
Field Vector ◽  
Magnetic Field Vector ◽  
Maximum Brightness ◽  
Time Variations ◽  
The Magnetic Field

Context. Penumbral microjets (PMJs) is the name given to elongated jet-like brightenings observed in the chromosphere above sunspot penumbrae. They are transient events that last from a few seconds to several minutes, and their origin is presumed to be related to magnetic reconnection processes. Previous studies have mainly focused on their morphological and spectral characteristics, and more recently on their spectropolarimetric signals during the maximum brightness stage. Studies addressing the temporal evolution of PMJs have also been carried out, but they are based on spatial and spectral time variations only. Aims. Here we investigate, for the first time, the temporal evolution of the polarization signals produced by short-lived PMJs (lifetimes < 2 min) to infer how the magnetic field vector evolves in the upper photosphere and mid-chromosphere. Methods. We use fast-cadence spectropolarimetric observations of the Ca II 854.2 nm line taken with the CRisp Imaging Spectropolarimeter at the Swedish 1 m Solar Telescope. The weak-field approximation (WFA) is used to estimate the strength and inclination of the magnetic field vector. By separating the Ca II 854.2 nm line into two different wavelength domains to account for the chromospheric origin of the line core and the photospheric contribution to the wings, we infer the height variation of the magnetic field vector. Results. The WFA reveals larger magnetic field changes in the upper photosphere than in the chromosphere during the PMJ maximum brightness stage. In the photosphere, the magnetic field inclination and strength undergo a transient increase for most PMJs, but in 25% of the cases the field strength decreases during the brightening. In the chromosphere, the magnetic field tends to be slightly stronger during the PMJs. Conclusions. The propagation of compressive perturbation fronts followed by a rarefaction phase in the aftershock region may explain the observed behavior of the magnetic field vector. The fact that such behavior varies among the analyzed PMJs could be a consequence of the limited temporal resolution of the observations and the fast-evolving nature of the PMJs.

scholarly journals Reading M87's DNA: A Double Helix Revealing a Large-scale Helical Magnetic Field

2021 ◽  
Vol 923 (1) ◽  
pp. L5
Author(s):  
Alice Pasetto ◽  
Carlos Carrasco-González ◽  
José L. Gómez ◽  
José-Maria Martí ◽  
Manel Perucho ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Double Helix ◽  
High Sensitivity ◽  
Polarization Degree ◽  
Very Large Array ◽  
Wide Range ◽  
Helical Magnetic Field ◽  
Helical Configuration ◽  
The Magnetic Field

Abstract We present unprecedented high-fidelity radio images of the M87 jet. We analyzed Jansky Very Large Array broadband full-polarization radio data from 4 to 18 GHz. The observations were taken with the most extended configuration (A configuration), which allows the study of the emission of the jet up to kiloparsec scales with a linear resolution of ∼10 pc. The high sensitivity and resolution of our data allow us to resolve the jet width. We confirm a double-helix morphology of the jet material between ∼300 pc and ∼1 kpc. We found a gradient of the polarization degree with a minimum at the projected axis and maxima at the jet edges and a gradient in the Faraday depth with opposite signs at the jet edges. We also found that the behavior of the polarization properties along the wide range of frequencies is consistent with internal Faraday depolarization. All of these characteristics strongly support the presence of a helical magnetic field in the M87 jet up to 1 kpc from the central black hole, although the jet is most likely particle-dominated at these large scales. Therefore, we propose a plausible scenario in which the helical configuration of the magnetic field has been maintained to large scales thanks to the presence of Kelvin–Helmholtz instabilities.

scholarly journals A Feedback Method to Improve the Dynamic Range and the Linearity of Magnetoimpedance Magnetic Sensor

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Dongfeng He
Keyword(s):  
Magnetic Field ◽  
Steel Plate ◽  
Dynamic Range ◽  
Magnetic Sensor ◽  
Magnetic Field Sensor ◽  
Amorphous Wire ◽  
Alloy Plate ◽  
Field Sensor ◽  
Feedback Method ◽  
The Magnetic Field

We developed a high-sensitivity magnetoimpedance magnetic field sensor using a FeCoSiB amorphous wire and a coil wound around it. The amorphous wire had the diameter of 0.1 mm and the length of 5 mm. The magnetic field resolution of about 20 pT/√Hz was achieved. But the dynamic range of the magnetoimpedance magnetic field sensor was only about ±0.7 Gauss, which was not enough for some applications, such as the defect evaluation of steel plate. The linearity of the system was also not good when big magnetic field was applied, which will cause some noise when the system is used in unshielded environment. We developed a feedback method to improve the dynamic range and the linearity of the magnetic field sensor. The operation point of the magnetic field sensor was fixed by sending a feedback current to the coil. Using the feedback method, the dynamic range was improved from ±0.7 Gauss to ±10 Gauss and the linearity was also improved over 100 times better. An eddy current testing system using the magnetic sensor was developed, and the crack defects in steel plate and in 3D-printed titanium alloy plate were evaluated.

Effect of Magnetic Field on the Magnetic Structure of Nanocrystalline Electroplated NiFe Layers

2005 ◽  
Vol 23 ◽  
pp. 167-170
Author(s):  
Xiao Ping Li ◽  
Z.J. Zhao ◽  
T.B. Oh ◽  
H.L. Seet
Keyword(s):  
Magnetic Field ◽  
Magnetic Structure ◽  
High Frequency ◽  
Longitudinal Magnetic Field ◽  
High Sensitivity ◽  
Frequency Range ◽  
Gmi Effect ◽  
Double Peaks ◽  
Field Sensor ◽  
The Magnetic Field

In order to develop high sensitivity micro sensors for bio-magnetic field using NiFe electroplated composite sensing elements, it is important to study how different plating processes can affect the magnetic properties in terms of the chemical composition and magnetic structure of the plated layer. In this study, to study the effect of the magnetic field on the magnetic structure of the electroplated NiFe layers, magnetic controlled plating in which a longitudinal magnetic field ranging from 0 to 400 Oe is applied during nanocrystalline electroplating of permalloy Ni80Fe20 layer of 2 µm thick onto a 20 µm diameter Cu wire. The magnetic structure of the plated layers is studied by investigating the Giant magneto-impedance (GMI) effect of the plated layer. GMI has been measured from a frequency range of 100 kHz to 50 MHz. It is observed that under conventional electroplating without an external magnetic controlling field, the anisotropy of the plated layer is generally circumferential as indicted by the double peaks of the MI curves in testing at high frequency. When a longitudinal magnetic field is applied during electroplating, the plated layer shows single peak MI curves, suggesting that the anisotropy is changed from circumferential to longitudinal. The results also show that the sensitivity and resolution of a magnetic field sensor is improved greatly by changing the anisotropy of the plated layer from circumferential to longitudinal.

Non‐oriented cesium sensors for airborne magnetometry and gradiometry

Geophysics ◽  
1984 ◽  
Vol 49 (11) ◽  
pp. 2024-2031 ◽  
Author(s):  
C. D. Hardwick
Keyword(s):  
Magnetic Field ◽  
National Research Council ◽  
Larmor Frequency ◽  
High Sensitivity ◽  
Field Vector ◽  
Error Characteristic ◽  
Optically Pumped ◽  
Optimal Angle ◽  
Multiple Sensor ◽  
The Magnetic Field

Optically pumped magnetometers are characterized by an optimal angle between their optical axes and the direction of the magnetic field they are sensing. Departure from the optimal angle causes a shift in the Larmor frequency with a corresponding error in the scalar value of the magnetic field being measured. To minimize this error, magnetometers are conventionally either mounted in multiple sensor clusters such that the errors tend to cancel, or they are mechanically oriented to maintain the optimal angle with respect to the magnetic field vector. Recent cesium vapor magnetometers using a split‐beam technique have a sufficiently flat error characteristic that they can be flown in a non‐oriented or “strap‐down” configuration. This configuration has advantages with respect to conventional methods in terms of reduced size and weight and of greatly reduced cost. This paper describes two fixed orientations for a particular split‐beam magnetometer and calculates the allowable maneuver envelope for all dip angles from 0 to 90 degrees. It is shown that the residual orientation errors can best be handled by the conventional type of magnetic interference compensation model that must, in any case, be implemented in digital form for high‐sensitivity magnetometry or for any type of gradiometry. The National Aeronautical Establishment (NAE) of the National Research Council of Canada has flown strap‐down magnetometers in a three‐axis gradiometer array in a Convair 580 for several years. Results for the entire normal maneuver envelope of the aircraft, including 30 degree bank turns, have equalled or surpassed those obtained with oriented magnetometers. Several typical maneuver compensation results are presented that gave root‐mean‐square (rms) (one‐sigma) residual errors as low as 0.03 gammas (γ) for total field and 3.5 mgammas/m (mγ/m) for lateral gradient.

Comparison of radio-auroral spectral characteristics at 398 MHz with incoherent scatter measurements of electric field

1980 ◽  
Vol 58 (2) ◽  
pp. 232-246 ◽  
Author(s):  
D. R. Moorcroft
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Phased Array ◽  
Spectral Characteristics ◽  
Line Of Sight ◽  
Doppler Velocity ◽  
Incoherent Scatter ◽  
Phase Velocities ◽  
Stream Drift ◽  
The Magnetic Field

Radio-auroral Doppler measurements obtained with the 398-MHz Homer phased-array radar were compared with simultaneous and coincident measurements of electron density and electric field made by the Chatanika incoherent scatter radar. The results for this post-midnight period of observation are not consistent with a direct relationship between the radio-auroral Doppler velocity and the line of sight component of the electron drift velocity, in contrast to the previous observations at VHF. Instead, the observations are consistent with the hypothesis that the echoes arise from the two-stream/drift-gradient irregularities traveling at their threshold phase velocities, close to the local acoustic velocity, Cs. Some of the Doppler velocities observed are considerably less than Cs, and may indicate propagation away from perpendicular to the magnetic field, possibly resulting from magnetic field line distortion.

scholarly journals An automatic magnetic field stabilizer of high sensitivity

1934 ◽  
Vol 145 (854) ◽  
pp. 250-257 ◽  
Keyword(s):  
Magnetic Field ◽  
High Sensitivity ◽  
Battery Voltage ◽  
Cavendish Laboratory ◽  
Counting Chamber ◽  
Coil Resistance ◽  
Magnet Coil ◽  
The Magnetic Field ◽  
A Current ◽  
Α Particles

The present paper describes a method whereby the field of an electromagnet can be kept constant automatically to at least one part in fifty thousand ( i. e. , to 0⋅2 gauss in 10,000 gauss) for long periods. The method has the great advantage of not merely ensuring that the current through the magnet (or, say, the voltage across the magnet windings) is kept constant, but that the field itself , as measured by a fluxmeter, is kept within one-fifth of a gauss (or less) of some desired value. Thus, it is not necessary to know whether a fluctuation of the field is caused by unsteadiness of the exciting battery voltage, variations of the magnet coil resistance with temperature, etc. ; in all cases, the stabilizer automatically readjusts the exciting current until the field is brought back to its original value. Further, as explained at the end of the paper, the stabilizer can be made to bring about an increase or decrease in the field of a definite number of gauss, and to continue to maintain the field at this new value. Also with very slight modifications, which are so obvious as to require no further explanation, the stabilizer could be made to maintain a current, or a potential difference, constant just as easily as a magnetic field. The method has been applied with success to the annular magnetic field used in the Cavendish Laboratory. The magnet is used for the analysis of α-particle groups. Under the influence of suitable fields of the order of 10,000 gauss, α-particles of various velocities are made to travel in a semicircle of 40 cm. radius, and are focussed on to the slit of a counting chamber. Groups of various velocities are focussed in turn by varying the field, their velocities being determined from the values of the fields. It is extremely important, therefore, to know the field strength with accuracy and to maintain it constant, at each of these values, during the experiment. In some experiments already described this was done manually. An observer watched the spot of light reflected from the mirror of a fluxmeter, the coil of which was connected to a stationary search coil situated in the magnetic field. A change of one-fifth of a gauss in the magnetic field produced a deflection of the fluxmeter spot of about 1 mm., and by suitable adjustment of the field current by means of a mercury rheostat it could be arranged that the spot was kept within half a millimetre of its zero portion. This, however, required one observer to spend his whole time in stabilizing the field during an experiment which might last several hours.

scholarly journals Multipoint observations of compressional Pc5 pulsations in the dayside magnetosphere and corresponding particle signatures

2020 ◽  
Vol 38 (6) ◽  
pp. 1267-1281
Author(s):  
Galina Korotova ◽  
David Sibeck ◽  
Mark Engebretson ◽  
Michael Balikhin ◽  
Scott Thaller ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Shift ◽  
Spectral Characteristics ◽  
Energetic Electron ◽  
Radial Distance ◽  
Frequency Doubling ◽  
Recovery Phase ◽  
Field Lines ◽  
G 13 ◽  
The Magnetic Field

Abstract. We use Van Allen Probes (Radiation Belt Storm Probes A and B, henceforth RBSP-A and RBSP-B) and GOES-13 and GOES-15 (henceforth G-13 and G-15) multipoint magnetic field, electric field, plasma, and energetic particle observations to study the spatial, temporal, and spectral characteristics of compressional Pc5 pulsations observed during the recovery phase of a strong geomagnetic storm on 1 January 2016. From ∼ 19:00 to 23:02 UT, successive magnetospheric compressions enhanced the peak-to-peak amplitudes of Pc5 waves with 4.5–6.0 mHz frequencies from 0–2 to 10–15 nT at both RBSP-A and RBSP-B, particularly in the prenoon magnetosphere. Poloidal Pc4 pulsations with frequencies of ∼ 22–29 mHz were present in the radial Bx component. The frequencies of these Pc4 pulsations diminished with increasing radial distance, as expected for resonant Alfvén waves standing along field lines. The GOES spacecraft observed Pc5 pulsations with similar frequencies to those seen by the RBSP but Pc4 pulsations with lower frequencies. Both RBSP-A and RBSP-B observed frequency doubling in the compressional component of the magnetic field during the Pc5 waves, indicating a meridional sloshing of the equatorial node over a combined range in ZSM from 0.25 to −0.08 Re, suggesting that the amplitude of this meridional oscillation was ∼ 0.16 Re about an equatorial node whose mean position was near ZSM=∼0.08 Re. RBSP-A and RBSP-B HOPE (Helium Oxygen Proton Electron) and MagEIS (Magnetic Electron Ion Spectrometer) observations provide the first evidence for a corresponding frequency doubling in the plasma density and the flux of energetic electrons, respectively. Energetic electron fluxes oscillated out of phase with the magnetic field strength with no phase shift at any energy. In the absence of any significant solar wind trigger or phase shift with energy, we interpret the compressional Pc5 pulsations in terms of the mirror-mode instability.

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