Magnetometer

摘要

1,209,637. Optical magnetometer. SINCLAIR RESEARCH Inc. Nov. 17, 1967 [Nov. 17, 1966 (2)], No.52352/67. Heading G1A. In a magnetometer comprising a contained body of optically excitable atoms which are acted upon by the field being measured, a source of resonance radiation impingeable upon and interacting with the body for producing alignment of the atoms, and means for directing on R. F. magnetic field of a frequency diminishing the alignment of atoms into the body and including a variable frequency oscillator the frequency of which is swept about a pumping frequency determined by the output of a radiation detector; means are provided for counting the frequency of the oscillator over an integral number of sweep cycles. In an optical magnetometer light from a source 20 Fig. 2 impinging on a detector 26 via a radiation absorption cell 22 is applied also to a detector 25 for reference purposes, the paths including collimating lenses 40, 48, polarizers 42 421 and a filter 44 which, if the gas in the cell is helium, may pass only 1À08 micron light. The cell outputs which may be resistive or voltaic are compared in for example a Wheatstone bridge and serve to control a variable oscillator 66 producing the depumping frequency for the cell. Alkalivapour, rubidium and cesium instruments as well as metastable helium are referred to. The arrangement is described in connection with geological surveying in an aeroplane bird. The frequency meter 138 Fig.3 includes a master oscillator and frequency dividers whereby a waveform is generated to sweep the depumping oscillator about its mean frequency and counting periods of the frequency meter are controlled by the same divider output so that the counting is always effected over a number of complete cycles. The absorption cell 112 may be excited by a discharge between electrodes in the cell, an R.F field, by a piece of radioactive material, or by X-rays, and the output of detector 120 is applied to adjust the depumping oscillator for maximum absorption through a phase controlled rectifier 134 fed also from the divider output, a pulse delay circuit 140 ensuring phase correspondence of wanted signals so that the rectifier serves also as a filter.