Rydberg Hydrogen Detector with n-state dependent Field Ionization Thesis for the Degree Master of Science in Applied Physics

The design of a detector for Rydberg Hydrogen atoms, capable of probing the distribution of n-states is investigated. The device is needed for the construction and commissioning of the AEgIS-apparatus at CERN, aiming to measure the gravitational interaction between matter and antimatter. The detector works by field ionizing the H atoms and consequently detecting the liberated electrons. Information about the n-state distribution can be extracted based on that different states field ionize at different field strengths. An analytical derivation of the electric field in the detector is obtained by solution of Laplace’s equation. The process of field ionization is also discussed. Together, this allows for the calculation of the ionization properties of the detector and hence the detection efficiencies for different n-states given a design choice of the detector. In the most extreme configuration, virtually all states with n ≥ 16 can be ionized somewhere in the detector but the tightly bound states only ionize in a small region where the electric field is the largest. The detection efficiency (which depends on the area in which a state ionizes) for different n states goes approximately linearly from 100% for n ≥ 27 to 0% for n ≤ 13. Ionization happens in a magnetic field of 1 T which should guide the ionization products downstream for detection. Particle tracking simulations show that this works well for electrons, which exhibit a very small cyclotron motion while protons exhibit a comparatively large cyclotron motion that in effect renders them inappropriate for detection.