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Implementation of a coherent Lyman-alpha source for laser cooling and spectroscopy of antihydrogen Michan, Juan Mario


This dissertation describes two related projects: the development of a coherent Lyman-α source and the implementation of a supersonic hydrogen beam. A two-photon resonance-enhanced four wave mixing process in krypton is used to generate high power coherent radiation at ωLy_α ⇒ 121.56 nm, the hydrogen Lyman-α line, to perform spectroscopy and cooling of magnetically trapped antihydrogen (1s − 2p transition). This is a tool to directly test both the Einstein Equivalence Principle and Charge, Parity, and Time inversion symmetry. The former can be tested by measuring the gravity interaction of matter and antimatter. Inversion symmetry can be tested by comparing the spectroscopic properties of hydrogen and antihydrogen. Both experiments require optically cooled antihydrogen. Under the current trapping conditions, optical cooling could be performed with nanosecond long pulses of 0.1 μJ of Lyman-α radiation at a repetition rate of 10 Hz. The process to generate Lyman-α radiation uses two wavelengths (ωR ⇒ 202.31 nm and ωT ⇒ 602.56 nm), which are mixed in a sum-difference scheme (ωLy_α = 2ωR−ωT ) with a two-photon resonance at (4s²4p⁵5p[1/2]₀ ← 4s²4p⁶(¹S₀) ). The source implemented produces 1.2 μW at the Lyman-α line and this was confirmed by performing spectroscopy of hydrogen. The design, implementation and characterization of the source are discussed in this dissertation. In the second part of the dissertation the implementation of the hydrogen beam and its characterization are discussed. The atomic hydrogen is generated with a thermal effusive source and it is entrained by an expanding noble gas. This process generates a cold beam of hydrogen atoms. Hydrogen is separated from the noble gas with a Zeeman bender that uses the forces generated by the Zeeman shift of low field seeking states of hydrogen and engineered magnetic field gradients. The hydrogen beam was characterized with a quadrupole mass spectrometer. The seed noble gas beam was characterized by colliding it with ultra-cold rubidium atoms in a magneto-optical trap. The trapped atoms loss rate resulting from these collisions can be used to measure the density of the atomic beam. This measurement demonstrates the potential of using magneto-optical traps as absolute flux monitors.

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