A Magneto-Optical Trap for Strontium James Millen A Magneto-Optical Trap for Strontium – Group meeting 29/09/08

Outline Optics Trapping strontium Laser system Physical layout Electronics Imaging the MOT Disaster strikes! Solution A Magneto-Optical Trap for Strontium – Group meeting 29/09/08

Trapping strontium A Magneto-Optical Trap for Strontium – Group meeting 29/09/08 Strontium has no appreciable vapour pressure at room temperature → An oven is required This hot beam of strontium needs to be slowed down to be trapped → A Zeeman slower is required The strontium is trapped in a Magneto-Optical Trap (MOT), which requires 3 pairs of counterpropagating beams (shown) and coils to produce a magnetic field (internal) Sr Oven

Laser System A Magneto-Optical Trap for Strontium – Group meeting 29/09/08 Spectroscopy: Locking our laser using POLWIS Imaging: For absorption imaging Zeeman Slower MOT beams -240MHz Toptica frequency doubled laser system at 461nm Double pass at +120MHz → 0 MHz (All frequencies quoted relative to the 5s 2 1 S 0 → 5s5p 1 P 1 transition in 88 Sr) Double pass at +120MHz → 0 MHz Double pass at -136MHz → +512 MHz Single pass at +200MHz → -40 MHz

Physical layout A Magneto-Optical Trap for Strontium – Group meeting 29/09/08

Physical layout A Magneto-Optical Trap for Strontium – Group meeting 29/09/08

Imaging the MOT A Magneto-Optical Trap for Strontium – Group meeting 29/09/08 Using a Photodiode we can gather temporal information about the MOT We need to be able to turn the MOT on and off remotely One has to be careful with the inductance of the coils Need a switching circuit that can also dump power when the coils are off

Switching circuit A Magneto-Optical Trap for Strontium – Group meeting 29/09/08 Follower Switch Feedback Integrator

Disaster! A Magneto-Optical Trap for Strontium – Group meeting 29/09/08 There are two MOT coils in our chamber, which can be electrically isolated One coil is shorted to the chamber (ground) + - Coil Power supply The power supply is floating, so who cares? The switch is grounded via the TTL supply. Current leaks about 1/3 rd of the way along the coil + Coil Power supply Switch

Solution A Magneto-Optical Trap for Strontium – Group meeting 29/09/08 Isolate the ground of the TTL using an optocoupler, and allow the switch to float.

Stop press! A Magneto-Optical Trap for Strontium – Group meeting 29/09/08 Coil switch on/off MOT fluorescence