Date of Award
Honors Thesis (Open Access)
Colby College. Physics and Astronomy Dept.
Duncan Tate, PhD
Apparatus for creating ultra-cold neutral plasmas (UNPs) was improved and data on plasma expansion was collected. We increase the trapping efficiency of a quadrupole magneto-optical trap (MOT) by installing a tapered amplifier to increase the power of the cooling laser used to trap atoms. We achieve an improvement in density of trapped atoms from 1 x 1010 cm-3 to 2.5 - 4.5 x 1010 cm-3. In addition, to improve precision and decrease systematic error, the magnetic field induced by inductive current in the MOT's anti-helmholtz coils was suppressed. This was achieved by installing a KEPCO Bipolar Power Supply, which allowed for suppression of induced current to sub 200 microAmpere magnitudes during the experiment.
Expansion velocity of rubidium UNPs was studied using ion time of flight (TOF) spectra collected for plasmas with initial electron temperatures of 1-150 K and initial ion temperatures of <100 microKelvin. We predicted a constant expansion velocity for a given initial electron temperature and our data generally agrees with this prediction well. However, for low initial electron temperatures and early in the plasma evolution we see a non-linear region. We suspect this is a result of the effects of three-body recombination. As such, we demonstrate that using ion TOF is a good way for studying spatial evolution of UNPs.
Ultra-cold Plasmas, Atom Trapping, Laser Cooling, Photoionisation
Recommended CitationBystrický, Jakub, "Apparatus Improvement and Characterisation for Experiments on Ultra-cold Plasmas." (2022). Honors Theses. Paper 1341.