A resistive-anode based position-sensitive Rydberg atom detector

We describe here the development and characterization of a position-sensitive detector for Rydberg atom experiments. The detector builds on an earlier design that field-ionized incident Rydberg positronium (Ps) atoms and then electrostatically focused the freed positrons onto a micro-channel plate (MCP) detector without the use of a position sensitive anode. In this design, pulses from the MCP are deposited onto a resistive anode, providing a means of measuring the incident particles' x, y positions. The first detector constructed utilized a pair of MCPs in a chevron configuration and was used to observe the focusing of Rydberg Ps atoms from an electrostatic mirror. A second detector, developed for use in a measurement of the 1S-2S interval of Ps, incorporates three MCPs in a Z-stack configuration to produce larger pulses. Using a UV-induced signal, we have characterized the performance of the assembled detectors, finding a spatial resolution of ∼1.4 mm for the largest induced pulses and for pulse widths of ∼7-10 ns FWHM; pulse times can be resolved to better than 1 ns. The Ps induced signal is anticipated to yield pulses ∼5 times larger, which are expected to achieve a spatial resolution of <1 mm. Appropriate lenses could make possible applications involving either imaging a large area or magnifying a small area of the incident Ps spatial distribution.