GB1076889A - Improvements in methods and devices for measuring the intensities of very weak magnetic fields - Google Patents

Abstract

1,076,889. Magnetometers. COMMISSARIAT A L'ENERGIE ATOMIQUE. Nov. 20, 1964 [Nov. 21, 1963], No. 47395/64. Heading G1N. In a magnetometer for measuring the intensity of weak magnetic fields of the order of 0À01 gauss in interplanetary space, two equal but opposite auxiliary magnetic fields H 1 , H 2 are created parallel to the field h to be measured in regions 1a, 1b respectively and the difference in Larmor frequency of protons in the respective resultant fields is measured. This difference is proportional to h. As shown, each vessel 4a, 4b may contain a solution of peroxylamine sulphate in deoxygenated water and an oscillator 7 delivers a signal to coils 5a, 5b to saturate the 56 Mc/s resonance line of the salt thereby increasing, due to the Overhauser- Abragam effect, the intensity of the signal at the Larmor frequency. Pick-up coils 8a, 8b form part of respective tuned circuits, e.g. 8a, 10a, each of which is connected to a linear amplifier, e.g. 11a, having a narrow pass band. Part of the output from each amplifier is fed back e.g. through resistor 13a to a coil 9a whose axis is perpendicular to that of coil 8a so that the only coupling between these coils is that due to nuclear magnetic resonance. Between the coils 5a, 5b and 8a, 9a, 8b, 9b is a screen (not shown) opaque to 56 Mc/s but transparent to the Larmor frequency (~ 10 kc/s). A mixer 15 forms the difference f = f 1 - f 2 of the frequencies f 1 , f 2 from outputs 12a, 12b and f is measured and recorded in known instruments 16, 17 respectively. Magnetic resonance generators such as described in Specification 1, 076, 700 may be used. Other paramagnetic substances which may be used in vessels 4a, 4b are aqueous diphenylpicrylhydrazyl and certain organic radicals containing a nitroxide group. The magnetometer is suitable for use in artificial satellites.