ISSN:
1365-2478
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Geosciences
,
Physics
Notes:
This paper describes the measurement of the Earth's total magnetic field by a determination of the frequency of free precession around this field of the protons in a sample of water. The angular frequency of precession, ω, is related to the field F by the relationship ω=γpF where γp is the gyromagnetic ratio of the proton.A bottle of water is magnetised in a direction approximately at right angles to the earth's field, by passing a current through a coil wound around the bottle. The current is switched off rapidly, leaving the magnetic moment vector to precess around the earth's field direction, inducing in the coil a small alternating voltage. This voltage is amplified and its frequency measured by means of a counter. The accuracy of measurement of the total field is estimated at ± 0.5γ.In addition to the total field value, the form of the signal voltage contains information on the field gradient across the sample.Simple theory, experimental details and results are given.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2478.1956.tb01392.x
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