High Current Stabilization Circuit for Ultracold Atom Trap Smita Speer, Howard University Mentor: Ryan Price, University of Maryland

Bose-Einstein Condensates in Lab Rubidium atoms travel through Zeeman slower where atoms are slowed by the nearly resonant pump laser (780nm). Rb atoms enter the magneto- optical trap (MOT) where lasers in orthogonal direction are used to cool the atoms further and a magnetic field is applied as a restoring force to keep atoms in place. Magnetic Trap is used to hold atoms while evaporative cooling reduces temperature of atoms to a few billionths of a degree above absolute zero [1,3]. Fig. 1. BCIT. 2003. BCIT MOT. [1] Cannon, Ben, Stone, Daniel, Price, Ryan. Light Analysis of Ultra-cold Magneto Optical Trap. [3] Steven Chu, The Manipulation of Neutral Particles. 1997. .

Effect on BECs Fluctuations in the current result in changes in the magnetic fields used to hold ultracold atoms. Magnetic traps are affected more noticeably by these fluctuations. If the magnetic fields vary, the atoms can become too hot, scatter and ruin results [2]. [2] Lee, S. –K., Romalis, M. V., J. Appl. Phys. 103, 084904 (2008).

Current Fluctuation The figure on the left is a breadboard in our lab used to measure how noisy our power source is and how it can be filtered by using bypass capacitors to stabilize voltage and power flow. Storing energy Blocking DC Fig. 2. Set up on breadboard in electronics lab Fig. 3. Electronics Bus. 2012. Bypass Capacitor Operation and Noise Ripple Characteristics

Operational Amplifier Configuration We designed an op amp set up to provide more stable current used in our experiment. Liquid Cooling Plates Set Up within Mounting Rack PA05 HS18

Controlling Op Amp To control the op amp, we designed a printed circuit board (pcb) to attach to the op amp’s pins. The pcb also offers us different ways to measure the current and compare with past methods for accuracy. Components on the board further stabilize the current outputting from the op amp. Resistors (current limit and compensation) Capacitors (Bypass and compensation Diodes and varistor (surge protection) Fig. 4. One of our resistors on a nickel

PCB Schematic & Board Designs

Finished Board

Set up within lab Current across op amp – current outputted Op amp set up

Conclusions Op amp design provides cleaner current. Can replace several supply coils in lab with external power source. Future tests of system Examine different methods of current measurement on pcb and on coils Design separate box for increased precision of control of the current