Method for detecting rotation with rapid start-up of an atomic gyroscope with SEOP

Patent metadata

Field	Value
Publication number	US-10684130-B2
Application number	US-201816015691-A
Country	US
Kind code	B2
Filing date	Jun 22, 2018
Priority date	Jun 28, 2017
Publication date	Jun 16, 2020
Grant date	Jun 16, 2020

Abstract

A method for detecting rotation of a carrier utilizes a device embedded in said carrier that comprises an enclosure containing a gaseous mixture of an alkali metal and a noble gas. The method includes a step of starting up (DEM-MEOP) the device during which the noble gas is polarised by utilizing metastability exchange optical pumping. The start-up step is followed by a step of acquisition (MES-SEOP) by the device of a signal representative of said rotation during which the noble gas is maintained polarised by utilizing spin exchange optical pumping. The invention extends to the device and to an inertial navigation unit integrating said device and to an inertial navigation method implementing the method for detecting rotation of the carrier.

First claim

The invention claimed is:

1. A method for detecting rotation of a carrier by a device embedded in said carrier, said device comprising an enclosure containing a gaseous mixture of an alkali metal and a noble gas, the method including:
a step of starting up the device during which the noble gas is polarised by means of metastability exchange optical pumping; and
following the step of starting up, a step of acquiring, by the device, a signal representative of said rotation during which the noble gas is maintained polarised by means of spin exchange optical pumping.

2. The method according to claim 1 , wherein the step of starting up is finished when the polarisation conferred on the noble gas by means of the metastability exchange optical pumping corresponds to a stationary polarisation conferred on the noble gas by means of the spin exchange optical pumping.

3. The method according to claim 2 , wherein the metastability exchange optical pumping includes an excitation of the noble gas by means of a first pump laser of which the power is controlled in such a way that the polarisation conferred on the noble gas by means of the metastability exchange optical pumping reaches the stationary polarisation.

4. The method according to claim 2 , wherein the step of starting up includes a sub-step of testing polarisation which includes:
stopping the metastability exchange optical pumping;
starting up the spin exchange optical pumping, carrying out a first measurement of the polarisation of the noble gas followed later by carrying out a second measurement of the polarisation of the noble gas;
if the result of the second measurement is greater than the result of the first measurement, stopping the spin exchange optical pumping and starting up again the metastability exchange optical pumping; and
if the result of the second measurement is less than the result of the first measurement, the step of starting up is finished.

5. The method according to claim 1 , wherein, during the step of starting up, the metastability exchange optical pumping is carried out in an auxiliary cell of the enclosure connected to a main cell of said enclosure by a diffusion connection of the gaseous mixture.

6. The method according to claim 5 , wherein the step of starting up includes:
closing a first valve arranged between the main cell and an intermediate cell ( 4 ) arranged in the diffusion connection of the gaseous mixture; and
opening a second valve arranged between the intermediate cell and the auxiliary cell.

7. An inertial navigation method including the detection of rotation of a carrier in accordance with the method according to claim 1 .

8. A device for detecting rotation, comprising an enclosure containing a gaseous mixture of an alkali metal and a noble gas, a first system for polarising the noble gas configured to carry out spin exchange optical pumping, and a second system for polarising the noble gas configured to carry out metastability exchange optical pumping, and a controller configured to:
during a step of starting up the device, selectively activating and controlling the second polarisation system in order to increase the polarisation of the noble gas; and
during a step, consecutive to the step of starting up, of acquiring, by the device, a signal representative of said rotation selectively activating and controlling the first polarisation system in order to maintain the polarisation of the noble gas.

9. The device according to claim 8 , wherein the alkali metal is potassium and the noble gas is helium 3.

10. The device according to claim 8 , wherein the enclosure includes a main cell and an auxiliary cell connected to the main cell by a diffusion connection of the gaseous mixture, and wherein the second polarisation system is configured to increase the polarisation of the noble gas in the auxiliary enclosure and the first polarisation system is configured to maintain the polarisation of the noble gas in the main enclosure.

11. The device according to claim 10 , further including an intermediate cell arranged in the diffusion connection of the gaseous mixture, a first valve arranged between the main cell and the intermediate cell and a second valve arranged between the intermediate cell and the auxiliary cell, and wherein the controller is further configured, during the start-up step, to close the first valve and open the second valve.

12. An inertial navigation unit including a device according to claim 8 .

Assignees

• Commissariat Energie Atomique
• Safran

Inventors

• Palacios Laloy Augustin

Classifications

• G01C19/60

  Electronic or nuclear magnetic resonance gyrometers · CPC title

• G01R33/26

  using optical pumping · CPC title

• G01C19/62 Primary

  with optical pumping · CPC title