Optical Pumping Magnetometer

• US 20130265042A1
• Filed: 03/14/2013
• Published: 10/10/2013
• Est. Priority Date: 04/06/2012
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: KANDORI, Akihiko, OSABE, Taro, KAWABATA, Ryuzo, SUZUKI, Seiichi, KAMADA, Yudai
• Granted Patent: US 9,366,735 B2
• Time in Patent Office: Days
• US Class Current: 324/301
• CPC Class Codes: G01R 33/26 using optical pumping

Abstract

Stable magnetic field measurement is enabled without collapse of polarization or fluctuation of intensity of a laser beam incident on a glass cell of an optical pumping magnetic sensor. Excitation light generated with a light source, having optimized light intensity and polarized wave, through frequency stabilization, intensity control and polarized-wave control, is introduced via a polarized wave holding optical fiber to a magnetic sensor provided in a magnetic shield, and magnetic field measurement is performed by optical pumping using magneto-optical properties of spin-polarized alkali metal. The magnetic sensor has a structure where a lens, a polarization optical device, the glass cell and a photodetector, are integrally accommodated in a non-magnetic case.

Claims

1. A magnetometer comprising:

a magnetic sensor, having a glass cell filled with alkali metal gas, that detects a magnetic field using magneto-optical properties of spin-polarized alkali metal;

a light source that generates frequency-stabilized excitation light introduced to the magnetic sensor;

a coil, provided in magnetic shield space including the magnetic sensor, that applies a static magnetic field and an RF magnetic field to the magnetic sensor; and

a signal processing device that lock-in detects a detection signal of light transmitted through the glass cell of the magnetic sensor, controls intensity of the static magnetic field and a frequency of the RF magnetic field generated from the coil based on a lock-in detection output, and obtains a measurement signal reflecting magnetic field intensity of a measurement subject set in the magnetic shield,

wherein the magnetic sensor has a structure where a collimator lens that the frequency-stabilized excitation light from the light source is introduced via a polarized wave holding optical fiber, a polarization optical device that transmits the excitation light passed through the collimator lens to the glass cell, and the glass cell, are integrally accommodated in a non-magnetic case.

2. The magnetometer according to claim 1,

wherein the magnetic sensor further has a photodetector device that detects the quantity of the light transmitted through the glass cell and outputs an electric signal, and

wherein the photodetector device is accommodated in the non-magnetic case.

3. The magnetometer according to claim 1,

wherein the magnetic sensor further has a light collecting lens, accommodated in the non-magnetic case, that collects the light transmitted through the glass cell on an end surface of a multi-mode optical fiber, and

wherein the magnetic sensor transmits the light via the multi-mode optical fiber to a photodetector provided outside the magnetic shield.

4. The magnetometer according to claim 1, further comprising a heat preserving mechanism that circulates warm water to a side surface of the glass cell of the magnetic sensor which the excitation light is not passed through.

5. The magnetometer according to claim 2, further comprising a heat preserving mechanism that circulates warm water to a side surface of the glass cell of the magnetic sensor which the excitation light is not passed through.

6. The magnetometer according to claim 3, further comprising a heat preserving mechanism that circulates warm water to a side surface of the glass cell of the magnetic sensor which the excitation light is not passed through.