Gravity gradiometer

Patent metadata

Field	Value
Publication number	US-11269111-B2
Application number	US-201816772517-A
Country	US
Kind code	B2
Filing date	Dec 14, 2018
Priority date	Dec 15, 2017
Publication date	Mar 8, 2022
Grant date	Mar 8, 2022

Abstract

The disclosure relates to a gravity gradiometer including a pair of magneto-optical traps for measuring a gravity gradient. A cold atom gravity gradiometer system includes comprising: first and second magneto-optical traps, each having a plurality of mirrored surfaces arranged to reflect an incident laser beam to trap respective first and second cold atom clouds separated from each other by a separation distance; an optical subsystem arranged to transmit a first laser beam in a first direction along a first longitudinal axis towards the first magneto-optical trap and a second laser beam in an opposite second direction along a second longitudinal axis towards the second magneto-optical trap, the second longitudinal axis being parallel to the first longitudinal axis.

First claim

The invention claimed is:

1. A cold atom gravity gradiometer system comprising:
first and second magneto-optical traps, each having a plurality of mirrored surfaces arranged to reflect respective first and second incident laser beams to trap respective first and second cold atom clouds separated from each other by a separation distance; and
an optical subsystem arranged to provide the first and second incident laser beams separately for the respective first and second magneto-optical traps and to transmit the first incident laser beam in a first direction along a first longitudinal axis towards the first magneto-optical trap and the second incident laser beam in an opposite second direction along a second longitudinal axis towards the second magneto-optical trap, the second longitudinal axis being parallel to the first longitudinal axis.

2. The cold atom gravity gradiometer system of claim 1 , wherein the first laser beam comprises a first cooling laser beam and a first atom interferometry beam, and the second laser beam comprises a second cooling laser beam and a second atom interferometry beam.

3. The cold atom gravity gradiometer system of claim 2 , wherein the first and second atom interferometry beams are substantially coaxial with the respective first and second cooling laser beams.

4. The cold atom gravity gradiometer system of claim 1 , comprising first and second intermediate reflection surfaces arranged to reflect the respective first and second laser beams back towards the respective first and second cold atom clouds.

5. The cold atom gravity gradiometer system of claim 1 , wherein each of the first and second magneto-optical traps comprise four mirrored surfaces angled with respect to the respective first and second intermediate reflection surfaces and arranged around the respective first and second longitudinal axes to reflect the respective first and second incident laser beams towards the respective first and second cold atom clouds.

6. The cold atom gravity gradiometer system of claim 1 , wherein the first longitudinal axis is substantially coincident with the second longitudinal axis.

7. The cold atom gravity gradiometer system of claim 4 , wherein the first and second intermediate reflection surfaces are arranged on the respective first and second longitudinal axes.

8. The cold atom gravity gradiometer system of claim 1 , wherein the second longitudinal axis is laterally offset from the first longitudinal axis.

9. The cold atom gravity gradiometer system of claim 4 , wherein the first and second intermediate reflection surfaces are arranged on a lateral axis between the first longitudinal axis and the second longitudinal axis, and wherein the system further comprises first and second deflection surfaces to deflect the laser beam onto the lateral axis from the first longitudinal axis and second longitudinal axis respectively.

10. The cold atom gravity gradiometer system of claim 9 , wherein the optical subsystem is further arranged to transmit a Raman beam along an atom interferometry axis towards the first and second magneto-optical traps, and wherein the angle between the atom interferometry axis and the first longitudinal axis is greater than 0°.

11. The cold atom gravity gradiometer system of claim 10 , wherein the optical subsystem is arranged to direct a first Raman beam towards the first magneto-optical trap in a first direction along the atom interferometry axis, and to direct a second Raman beam towards the second magneto-optical trap in an opposite, second direction along the atom interferometry axis.

12. The cold atom gravity gradiometer system of claim 10 , further comprising a Raman mirror positioned along the atom interferometry axis after the first and second magneto-optical traps, and arranged to reflect the Raman beam back along with atom interferometry axis towards the second and first magneto-optical traps.

13. The cold atom gravity gradiometer system of claim 4 wherein the first and second intermediate reflection surfaces are arranged to reflect the respective first and second incoming laser beams away from a central region between the first and second magneto-optical traps.

14. The cold atom gravity gradiometer system of claim 4 , wherein the first and second intermediate reflection surfaces form opposing first and second surfaces of an intermediate reflector.

15. A cold atom gravity gradiometer system comprising:
first and second magneto-optical traps, each having a plurality of mirrored surfaces arranged to reflect an incident laser beam to trap respective first and second cold atom clouds separated from each other by a separation distance; and
an optical subsystem arranged to transmit a first laser beam in a first direction along a first longitudinal axis towards the first and second magneto-optical traps and a second laser beam in an opposite second direction along a second longitudinal axis towards the second and first magneto-optical traps,
wherein the first magneto-optical trap is arranged on the first longitudinal axis and the second magneto-optical trap is arranged on the second longitudinal axis, and wherein the second longitudinal axis is parallel to and laterally offset from the first longitudinal axis.

16. The cold atom gravity gradiometer system of claim 15 , wherein the system comprises:
a first deflection surface arranged to deflect the first laser beam from the first longitudinal axis onto a lateral axis between the first and second longitudinal axes, and to deflect the second laser beam from the lateral axis onto the first longitudinal axis; and
a second deflection surface arranged to deflect the second laser beam from the second longitudinal axis onto the lateral axis, and to deflect the first laser beam from the lateral axis onto the second longitudinal axis.

17. The cold atom gravity gradiometer system of claim 1 , wherein the system is rotatable around at least one rotation axis.

18. The cold atom gravity gradiometer system of claim 1 wherein the first and second magneto-optical traps are disposed within respective first and second vacuum chambers.

19. The cold atom gravity gradiometer system of claim 18 wherein the first and second vacuum chambers are connected to a vacuum system disposed at least partially between the first and second vacuum chambers.

20. The cold atom gravity gradiometer system of claim 1 wherein the separation distance is adjustable.

21. A method comprising:
determining a gravity gradient using a gravity gradiometer system comprising:
first and second magneto-optical traps, each having a plurality of mirrored surfaces arranged to reflect respective first and second incident laser beams to trap respective first and second cold atom clouds separated from each other by a separation distance; and
an optical subsystem arranged to provide the first and second incident laser beams separately for the respective first and second magneto-optical traps and to transmit the first incident laser beam in a first direction along a first longitudinal axis towards the first magneto-optical trap and the second incident laser beam in an opposite second direction along a second longitudinal axis towards the second magneto-optical trap, the second longitudinal axis being parallel to the first longitudinal axis, wherein the first longitudinal axis is offset from the second longitudinal axis,

wherein the determining a gravity gradient comprises:
measuring a first gravity difference between the first magneto-optical trap and second magneto

Assignees

• Univ Birmingham

Inventors

• Lamb Andrew
• De Villiers Geoff
• Holynski Michael
• Bongs Kai

Classifications

• G01V7/14 Primary

  using free-fall time · CPC title

• G01V7/04 Primary

  Electric, photoelectric, or magnetic indicating or recording means · CPC title

• G01N21/65

  Raman scattering · CPC title