Transcript Towards a strontium pyramid MOT

Towards a strontium pyramid MOT
Graham Lochead
Durham University
http://massey.dur.ac.uk/
Graham Lochead
YAO 2009
Colleagues
Strontium Rydberg experiment
Matt Jones
Supervisor
James Millen
PhD student
Graham Lochead
YAO 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 Lochead
YAO 2009
Overview of strontium
• Alkaline-earth element
• Atomic number 38
• Two electrons in outer shell
• Four stable isotopes:
84 Sr
86 Sr
87 Sr
88 Sr
0.6%
9.9%
7%
82.5%
I=0
I=0
I=9/2
I=0
Graham Lochead
YAO 2009
boson
boson
fermion
boson
Overview of strontium: Electronic structure
412 nm
1P
1
3P
1D
2
461 nm
/2p = 32 MHz
2
689 nm
/2p = 7.5 kHz
1
0
698nm
/2p = 1 mHz 87Sr
1S
0
• 1S0 ground state – no x • Broad linewidth for 1S0-
optical pumping
• Low decay rate to
xxmeta-stable state 3P2
1P
1
transition
• Intercombination line
x for further cooling
Graham Lochead
YAO 2009
Cold atomic uses for strontuim
• Ultracold atomic plasmas
• Optical lattice clocks
From Killian et al., physics/0612097
Graham Lochead
YAO 2009
Durham strontium experiment
Ultracold Rydberg state strontium
atoms in an optical lattice
Graham Lochead
YAO 2009
Aims of our experiment
Aims
• 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
Graham Lochead
YAO 2009
Experimental setup
Graham Lochead
YAO 2009
Achievements
• Single stage cooling
to a MOT at 461nm
• Labview computer
control setup
• MCP tested
Graham Lochead
YAO 2009
How does the pyramid MOT fit in?
Graham Lochead
YAO 2009
What is a pyramid MOT?
Normal (6 beam) MOT
Pyramid MOT
Three pairs of counterpropagating beams
Single beam with four mirror
creating the same optical geometry
K. J. Weatherill PhD thesis (2007)
Graham Lochead
YAO 2009
Pyramid MOT function
Used as cold atomic source
Graham Lochead
YAO 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 Lochead
YAO 2009
Our pyramid MOT design
• First strontium
pyramid MOT
• Based on dispensers
• Novel design
Graham Lochead
YAO 2009
The novelty in our design
Problem
• Source of hot atoms above mirrors to load MOT
• Hot strontium reacts with glass – coating mirrors
Solution
• Dispensers below mirrors
• Slits where mirrors meet in corners
Graham Lochead
YAO 2009
Novel design
Graham Lochead
YAO 2009
Progress so far
• Everything designed and ordered
• Waiting for chamber and mount
Graham Lochead
YAO 2009
Dispenser cell
Dispensers used
before to create a nonpumped, buffer
gasless reference cell
E. M. Bridge, et al. Rev. Sci. Instrum. 80, 013101 (2009)
Graham Lochead
YAO 2009
Second generation dispenser cell
New cell becomes
optically thick
Saturated absorption
spectroscopy in new cell
Graham Lochead
YAO 2009
Summary
1P
1
3P
1D
2
2
1
0
1S
0
Graham Lochead
YAO 2009