scholarly journals Bidirectional, Analog Current Source Benchmarked with Gray Molasses-Assisted Stray Magnetic Field Compensation

2021 ◽  
Vol 11 (21) ◽  
pp. 10474
Author(s):  
Jakub Dobosz ◽  
Mateusz Bocheński ◽  
Mariusz Semczuk
Keyword(s):  
Magnetic Field ◽  
Laser Cooling ◽  
Current Source ◽  
Three Dimensional ◽  
Electrical Current ◽  
Ultracold Atom ◽  
Experimental Chamber ◽  
Flexible Control ◽  
Alkali Atoms ◽  
Doppler Cooling

In ultracold-atom and ion experiments, flexible control of the direction and amplitude of a uniform magnetic field is necessary. It is achieved almost exclusively by controlling the current flowing through coils surrounding the experimental chamber. Here, we present the design and characterization of a modular, analog electronic circuit that enables three-dimensional control of a magnetic field via the amplitude and direction of a current flowing through three perpendicular pairs of coils. Each pair is controlled by one module, and we are able to continuously change the current flowing thorough the coils in the ±4 A range using analog waveforms such that smooth crossing through zero as the current’s direction changes is possible. With the electrical current stability at the 10−5 level, the designed circuit enables state-of-the-art ultracold experiments. As a benchmark, we use the circuit to compensate stray magnetic fields that hinder efficient sub-Doppler cooling of alkali atoms in gray molasses. We demonstrate how such compensation can be achieved without actually measuring the stray fields present, thus speeding up the process of optimization of various laser cooling stages.

Modeling and Designing an Intelligent Controller using Bond Graph for a Satellite Controlled by Magnetic Actuators

2012 ◽  
Vol 2 (1) ◽  
pp. 72-90 ◽  
Author(s):  
Majid Habibi ◽  
Alireza B. Novinzadeh
Keyword(s):  
Magnetic Field ◽  
Three Dimensional ◽  
Electrical Current ◽  
Bond Graph ◽  
Control Logic ◽  
State Equations ◽  
Magnetic Actuators ◽  
Advantages And Disadvantages ◽  
Aerospace Technology ◽  
Short Time

Satellite state control has always been an important topic in aerospace technology. Because it is required that when the satellite is stationary in orbit, it would be directed to a special object and this task should be performed in a situation where there isn’t access to the satellite. This task is performed using various technologies and one of these is the use of magnetic actuators. Magnetic actuators use mechanical torque that is resulted by interaction of electrical current of coils in the satellite and the earth’s magnetic field. The satellite is subjected to such disturbance torques, thus corrupting the direction of the satellite. This method has its advantages and disadvantages. Its drawback is that the magnetic torque is produced only perpendicular to the direction of the magnetic field and the axis of the coil. This paper models a satellite having magnetic actuators using bond graph, and finds out its state equations, and then constructs the control logic that is needed for its control. A model of three dimensional attitude maneuvers and magnetic systems using bond graph is described. The actuators are tuned using the method of particle swarm optimization (PSO). It is observed that using this method a small satellite reaches to the desired angle in a short time and becomes stationary.

Current Source Design for 3D Magnetic Field Simulation

2013 ◽  
Vol 760-762 ◽  
pp. 1354-1359
Author(s):  
Zhi Li ◽  
Shu Bao Pan
Keyword(s):  
Magnetic Field ◽  
Design Principle ◽  
Current Source ◽  
Three Dimensional ◽  
Calibration Method ◽  
Constant Current ◽  
Constant Current Source ◽  
Precision Error ◽  
Magnetic Field Simulation ◽  
A Current

This paper designs a current source which is used for simulating the three dimensional magnetic field. Gives the circuit schematic, Analyzes the design principle of the circuit and puts forward the calibration method of software which is suitable for the operation in microprocessor and improves the output accuracy of the constant current source. Actual test shows that the output of the constant current source is 0.1mA-500mA and the precision error is less than 0.03% of full scale. It has been used in the degaussing device testing and maintenance. The performance is stable and reliable achieves good results.

scholarly journals Sub-Doppler laser cooling of $^{39}$K via the 4S$\to$5P transition

2019 ◽  
Vol 6 (4) ◽  
Author(s):  
Govind Unnikrishnan ◽  
Michael Gröbner ◽  
Hanns-Christoph Nägerl
Keyword(s):  
Magnetic Field ◽  
Phase Space ◽  
Laser Cooling ◽  
Vibrational Level ◽  
Optical Lattice ◽  
Optical Pumping ◽  
Phase Space Density ◽  
Peak Density ◽  
Alkali Atoms ◽  
Spin Polarized

We demonstrate sub-Doppler laser cooling of ^{39}39K using degenerate Raman sideband cooling via the 4S_{1/2} \rightarrow1/2→5P_{1/2}1/2 transition at 404.8 nm. By using an optical lattice in combination with a magnetic field and optical pumping beams, we obtain a spin-polarized sample of up to 5.6 \times 10^{7}5.6×107 atoms cooled down to a sub-Doppler temperature of 4 \upmuμK, reaching a peak density of 3.9 \times 10^{9}3.9×109 atoms/cm^{3}3, a phase-space density greater than 10^{-5}10−5, and an average vibrational level of \langle \nu \rangle=0.6⟨ν⟩=0.6 in the lattice. This work opens up the possibility of implementing a single-site imaging scheme in a far-detuned optical lattice utilizing shorter wavelength transitions in alkali atoms, thus allowing improved spatial resolution.

Computational Modeling For Magnetic-Sensor-Based Three-Dimensional Visualization Of Microcracks

2001 ◽  
Vol 674 ◽  
Author(s):  
Leonid Muratov ◽  
David Lederman ◽  
Bernard R. Cooper
Keyword(s):  
Magnetic Field ◽  
Three Dimensional ◽  
Magnetic Tunnel Junction ◽  
Phase Segregation ◽  
Surface Region ◽  
Electrical Current ◽  
Element Analysis ◽  
Near Surface ◽  
Fast Recognition ◽  
The Magnetic Field

ABSTRACTThe presence of cracks, phase segregation, or even submicron-sized grain boundaries creates a disruption of the magnetic field response to an externally applied electrical current running through the material. These effects can be detected through the magnetic field leakage in the external near-surface region. Using a computer model of an array of magnetic tunnel junction detectors, magnetic “signatures” of various faults and/or material borders and domains have been calculated using finite element analysis and portrayed by icons. We have considered a number of typical cracks and flaws, of different dimensions and orientations, within the bulk of the component. The database of “signatures” thus generated allows fast recognition of faults and generation of their images in real time. Significant efforts have been made to provide an adequate three-dimensional visualization of the shape and distribution of microcracks, the magnetic field lines, and delineation of the position of the faults in relation to the surface.

Multiple characteristics of three‐dimensional radiative Cross fluid with velocity slip and inclined magnetic field over a stretching sheet

Heat Transfer ◽  
2021 ◽  
Author(s):  
Hafiz Abdul Wahab ◽  
Syed Zahir Hussain Shah ◽  
Assad Ayub ◽  
Zulqurnain Sabir ◽  
Muhammad Bilal ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Stretching Sheet ◽  
Three Dimensional ◽  
Velocity Slip ◽  
Inclined Magnetic Field ◽  
Multiple Characteristics

Magneto convective flow of casson nanofluid due to Stefan blowing in the presence of bio-active mixers

2021 ◽  
pp. 239779142110166
Author(s):  
Venkatesh Puneeth ◽  
Sarpabhushana Manjunatha ◽  
Bijjanal Jayanna Gireesha ◽  
Rama Subba Reddy Gorla
Keyword(s):  
Magnetic Field ◽  
Brownian Motion ◽  
Convective Flow ◽  
Three Dimensional ◽  
Induced Magnetic Field ◽  
Density Profiles ◽  
Casson Nanofluid ◽  
And Brownian Motion ◽  
Similarity Transformations ◽  
The Mathematical Model

The induced magnetic field for three-dimensional bio-convective flow of Casson nanofluid containing gyrotactic microorganisms along a vertical stretching sheet is investigated. The movement of these microorganisms cause bioconvection and they act as bio-active mixers that help in stabilising the nanoparticles in the suspension. The two forces, Thermophoresis and Brownian motion are incorporated in the Mathematical model along with Stefan blowing. The resulting model is transformed to ordinary differential equations using similarity transformations and are solved using [Formula: see text] method. The Velocity, Induced Magnetic field, Temperature, Concentration of Nanoparticles, and Motile density profiles are interpreted graphically. It is observed that the Casson parameter decreases the flow velocity and enhances the temperature, concentration, and motile density profiles and also it is noticed that the blowing enhances the nanofluid profiles whereas, suction diminishes the nanofluid profiles. On the other hand, it is perceived that the rate of heat conduction is enhanced with Thermophoresis and Brownian motion.

scholarly journals The on-axis magnetic well and Mercier's criterion for arbitrary stellarator geometries

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
P. Kim ◽  
R. Jorge ◽  
W. Dorland
Keyword(s):  
Magnetic Field ◽  
Original Work ◽  
Three Dimensional ◽  
Radial Distance ◽  
Analytical Form ◽  
One Dimensional ◽  
Modern Notation ◽  
Magnetic Well ◽  
First Time ◽  
Dimensional Integral

A simplified analytical form of the on-axis magnetic well and Mercier's criterion for interchange instabilities for arbitrary three-dimensional magnetic field geometries is derived. For this purpose, a near-axis expansion based on a direct coordinate approach is used by expressing the toroidal magnetic flux in terms of powers of the radial distance to the magnetic axis. For the first time, the magnetic well and Mercier's criterion are then written as a one-dimensional integral with respect to the axis arclength. When compared with the original work of Mercier, the derivation here is presented using modern notation and in a more streamlined manner that highlights essential steps. Finally, these expressions are verified numerically using several quasisymmetric and non-quasisymmetric stellarator configurations including Wendelstein 7-X.

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