Graham LocheadYAO 2009

Towards a strontium pyramid MOT

Graham Lochead

Durham University

http://massey.dur.ac.uk/

Graham LocheadYAO 2009

Colleagues

Strontium Rydberg experiment

Matt JonesSupervisor

James MillenPhD student

Graham LocheadYAO 2009

Outline

• Overview of strontium– Structure and uses

• Our experiment– Aims and achievements

• Pyramid MOT– What is a pyramid MOT?– Why is it beneficial?– Our design

• Progress so far• Summary

Graham LocheadYAO 2009

Overview of strontium

• Alkaline-earth element

• Atomic number 38

• Two electrons in outer shell

• Four stable isotopes:

84 Sr 0.6% I=0 boson86 Sr 9.9% I=0 boson87 Sr 7% I=9/2 fermion88 Sr 82.5% I=0 boson

Graham LocheadYAO 2009

Overview of strontium: Electronic structure

1S0

1P1

1D2

461 nm/2 = 32 MHz

3P2

1

0689 nm/2 = 7.5 kHz

412 nm

698nm/2 = 1 mHz 87Sr

• 1S0 ground state – no x optical pumping• Low decay rate to xxmeta-stable state 3P2

• Broad linewidth for 1S0- 1P1 transition• Intercombination line x for further cooling

Graham LocheadYAO 2009

Cold atomic uses for strontuim

• Ultracold atomic plasmas

• Optical lattice clocks

From Killian et al., physics/0612097

Graham LocheadYAO 2009

Durham strontium experiment

Ultracold Rydberg state strontium atoms in an optical lattice

Graham LocheadYAO 2009

Aims of our experiment

• Two stage cooling to make ultracold• Optical lattice from two counter-propagating

beams from same laser (532nm)• Excite to a Rydberg state• Observe following dynamics

Aims

Graham LocheadYAO 2009

Experimental setup

Graham LocheadYAO 2009

Achievements

• Single stage cooling to a MOT at 461nm

• Labview computer control setup

• MCP tested

Graham LocheadYAO 2009

How does the pyramid MOT fit in?

Graham LocheadYAO 2009

What is a pyramid MOT?

Normal (6 beam) MOT Pyramid MOT

Three pairs of counter-propagating beams

Single beam with four mirror creating the same optical geometry

K. J. Weatherill PhD thesis (2007)

Graham LocheadYAO 2009

Pyramid MOT function

Used as cold atomic source

Graham LocheadYAO 2009

Benefits of a pyramid MOT

• Size – much smaller than a Zeeman slower

• Simpler to build than complex magnetic field in ZS• Simpler optical alignment than 2D mot or funnel• No thermal atoms disrupting experiment

Graham LocheadYAO 2009

Our pyramid MOT design

• First strontium pyramid MOT

• Based on dispensers

• Novel design

Graham LocheadYAO 2009

The novelty in our design

• Source of hot atoms above mirrors to load MOT• Hot strontium reacts with glass – coating mirrors

Problem

Solution

• Dispensers below mirrors• Slits where mirrors meet in corners

Graham LocheadYAO 2009

Novel design

Graham LocheadYAO 2009

Progress so far

• Everything designed and ordered

• Waiting for chamber and mount

Graham LocheadYAO 2009

Dispenser cell

Dispensers used before to create a non-pumped, buffer gasless reference cell

E. M. Bridge, et al. Rev. Sci. Instrum. 80, 013101 (2009)

Graham LocheadYAO 2009

Second generation dispenser cell

New cell becomes optically thick

Saturated absorption spectroscopy in new cell

Graham LocheadYAO 2009

Summary

1S0

1P11D2

3P210