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Helmholtz coil

1. Helmholtz Coil Structure and Functionality: – Helmholtz coil pair comprises two identical circular magnetic coils. – Coils are symmetrically placed along a common axis […]

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1. Helmholtz Coil Structure and Functionality:

– Helmholtz coil pair comprises two identical circular magnetic coils.
– Coils are symmetrically placed along a common axis with a separation equal to the coil’s radius.
– Each coil carries an equal electric current in the same direction.
– Anti-Helmholtz coil creates a region of nearly uniform magnetic field gradient.
– Helmholtz coils consist of wire turns.
– Equations for magnetic field induction along the axis and distance-dependent field calculation.
– Field strength formulas for multi-turn coils and calculations at different points in the pair.
– Similar structure to solenoids, used for testing composite materials to low-frequency magnetic fields.

2. Time-Varying Magnetic Fields and Applications:

– Many applications necessitate time-varying magnetic fields.
– Applications include scientific experiments and biomedical studies.
– AC Helmholtz coil driver is used to generate time-varying fields.
– Required fields can be pulse or continuous sinewave with a frequency range from near DC to megahertz.

3. Helmholtz Coil Driver and High-Frequency Resonance:

– Equation to calculate coil current for a desired magnetic field.
– Use of function generator and high-current waveform amplifier driver.
– Calculation of required Helmholtz coil driver amplifier voltage.
– Parameters involved in calculating the amplifier voltage.
– Importance of driver voltage and current for generating magnetic fields.
– Challenges of generating high-frequency magnetic fields.
– Series resonant circuit and capacitor addition for high-frequency resonance.

4. Comparison with Halbach Arrays and Magnetism:

– Differentiation between Helmholtz coils and Halbach arrays.
– Helmholtz coils trap charged particles with their diverging field lines.
– Reversing a coil creates a cusp trap for charged particles.
– Halbach arrays serve different purposes in magnetism.

5. Research and Publications:

– Edward Ramsden’s book focuses on Hall-effect sensors, theory, and applications.
– Ramsden’s work is a valuable resource with the ISBN 978-0-75067934-3.
– Helmholtz coils’ role in generating high-frequency magnetic fields and resonance.
– ASACUSA MUSASHI group’s research on Helmholtz coil fields and significant contributions to understanding them.

Helmholtz coil (Wikipedia)

A Helmholtz coil is a device for producing a region of nearly uniform magnetic field, named after the German physicist Hermann von Helmholtz. It consists of two electromagnets on the same axis, carrying an equal electric current in the same direction. Besides creating magnetic fields, Helmholtz coils are also used in scientific apparatus to cancel external magnetic fields, such as the Earth's magnetic field.

A Helmholtz coil
Helmholtz coil schematic drawing

When the pair of two electromagnetics of a Helmholtz coil carry an equal electric current in the opposite direction, it is known as anti-Helmholtz coil, which creates a region of nearly uniform magnetic field gradient, and is used for creating magnetic traps for atomic physics experiments.

A beam of cathode rays in a vacuum tube bent into a circle by a Helmholtz coil
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