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Expansion Of An Ultracold Neutral Plasma, Yin Li
Expansion Of An Ultracold Neutral Plasma, Yin Li
Honors Theses
Ultracold neutral plasmas (UNP) exhibit interesting behavior and are more feasible to control than hot plasmas. Physicists would like to lower the temperature of a UNP to achieve a higher Coulomb coupling parameter, Γ for both electrons and ions. However, the three body recombination (TBR) between ions and electrons produces Rydberg atoms and heats up the plasma electrons, thereby ionizing them to Γe < 0.2. Adding Rydberg atoms to the plasma will reduce the temperature of a UNP in certain situations. In this honors project, we tried to achieve a Γe value greater than 0.5 by embedding Rydberg atoms multiple times in the plasma. We did extensive numerical simulations, but we were unable to replicate previous results from another group which obtained Γe = 0.5 in the first 1 µ s of plasma evolution. However, we were able to use the simulation results to test various different experiment scenarios. For experiments, we created a UNP of Rubidium atoms in the magneto-optical trap by laser cooling and photoionization. We figured out a nice way to zero the electric field within the field meshes by looking at the plasma expansion very late in its evolution through the micro-channel plate. We set the voltage and delay on the field mesh bias to find expansion velocity of the plasma for time t > 50 µs, and we used different methods to deduce the expansion velocity from the ion time of flight signals. However, we found that there was no relation of Γe at 1 µ s and the expansion velocity …
Resonant Collisions Of Potassium Atoms, Philip Michael Adamson
Resonant Collisions Of Potassium Atoms, Philip Michael Adamson
Honors Theses
This thesis discusses an approach to excite potassium atoms to very highly excited states (Rydberg states), and then tune their energy levels to induce resonant collisions between atoms. Potassium gas is super-cooled to 1 mK and confined to a small volume in a magneto-optical trap. A 405 nm laser diode, electronically locked to a potassium vapor cell via Doppler free spectroscopy, excites these atoms from the 4s1/2 state (ground state) to the 5p3/2 state. A 978 nm laser then excites the 5p3/2 to nd3/2 or nd5/2 transition, creating Rydberg atoms. Since there is no ground …