Texas Instruments Corporation

Douglas D McGregor

Bela I Marton

Forrest D Colegrove

Joseph A Rice, Jr

A magnetometer having an enclosed cell containing He.sup.3 therein for receiving light from a light source, a light source for directing light to the enclosed cell along a predetermined path, a single pick-up coil containing therein the light source and the enclosed cell, a solenoid containing the pick-up coil therein and a data collection system coupled to the pick-up coil. The light source is a source of circularly polarized light and can comprise a He.sup.4 cell and an optical system and a circular polarizer disposed serially between He.sup.4 cell and enclosed cell containing He.sup.3. The predetermined path of the light source, the enclosed cell and the pick-up coil are disposed along the axis of the solenoid. The light source can also be a laser.

He.sup.3 solenoid magnetometer

A helium magnetometer includes a helium cell containing helium, preferable .sup.4 He. A solid state laser strikes the helium cell at one end with a laser having a wave length of 1082.91 nm in the embodiment of a .sup.4 He cell. The helium atoms precess at known frequencies for different magnetic fields. The transparency of the helium cell at 1082.91 nm with .sup.4 He is a function of the resonance of the atoms within the helium cell. A radiation detector positioned on a second end of the helium cell opposite the end where the laser strikes detects the laser when transmitted through the helium cell and produces an electrical signal in response to the transmitted laser. The resonance of the helium cell is enhanced by a Voltage Controlled Oscillator, VCO, which provides a variable output frequency to a pair of coils positioned on the sides of the helium cell and electrically connected to the VCO to receive the variable output frequency. The pair of coils produces a variable magnetic field at the precession frequency that is mathematically related to the magnetic field that is being measured and thus enhances the precession of the atoms within the helium cell. A feedback loop includes a demodulation circuit that is electrically connected between the radiation detector and the VCO and demodulates the electrical signal from the radiation detector to produce a drive voltage for driving the VCO.

Laser driven helium magnetometers

A smart mine includes a pair of He.sup.3 magnetic sensors exteriorly connected to a head compartment of a mine housing. A torpedo compartment for housing a torpedo completes the mine housing. The head compartment contains the sensor support electronics which includes a phase locked loop means having a pair of digital phase locked loops connected between the sensors and a difference circuit whereby a difference signal representative of the difference between the pair of He.sup.3 magnetic sensors is produced for processing in a signal processor for determining the presence of large ferromagnetic bodies and producing a torpedo firing signal.

Smart mine

An apparatus for measuring the magnitude of a magnetic field in one embodiment includes a .sup.3 He cell having an oscillator connected thereto for producing an electrical discharge for metastable .sup.3 He atoms, a .sup.4 He lamp having an oscillator connected thereto for producing .sup.4 He radiation and an optical path to the .sup.3 He cell including a lens for collimating the .sup.4 He radiation and a circular polarizer. The imaged .sup.3 He atoms and .sup.4 He radiation interact to magnetize a portion of the .sup.3 He atoms in a direction parallel to the direction of the ambient magnetic field. After the cell magnetization, an oscillatory magnetic field normal to the ambient field is established by coils connected to a frequency synthesizer which is scanned over a frequency interval including the free precession (Larmor) frequency. This action rotates the direction of magnetization of the .sup.3 He cell atoms from parallel to the ambient magnetic field to approximately perpendicular to the ambient magnetic field. The cell then is allowed to precess freely and an a.c. is induced in a coil during precession. The a.c. is connected to a frequency discriminator which may be a digital type to digitize the voltage representative of the frequency of the a.c. A very narrow band digital filter filters the digitized output of the discriminator and a digital to analog converter produces a voltage from the digital filter output for a charge recorder for charting.

Growing community of inventors

Plano, TX, United States of America

Douglas D McGregor