# Trapped Antihydrogen in Its Ground State

 Title: Trapped Antihydrogen in Its Ground State Author: Richerme, Philip Citation: Richerme, Philip. 2012. Trapped Antihydrogen in Its Ground State. Doctoral dissertation, Harvard University. Full Text & Related Files: Richerme_gsas.harvard_0084L_10081.pdf (7.615Mb; PDF) Abstract: Antihydrogen atoms $$(\bar{H})$$ are conﬁned in a magnetic quadrupole trap for 15 to 1000 s - long enough to ensure that they reach their ground state. This milestone brings us closer to the long-term goal of precise spectroscopic comparisons of $$\bar{H}$$ and H for tests of CPT and Lorentz invariance. Realizing trapped $$\bar{H}$$ requires characterization and control of the number, geometry, and temperature of the antiproton $$(\bar{p})$$ and positron $$(e^+)$$ plasmas from which $$\bar{H}$$ is formed. An improved apparatus and implementation of plasma measurement and control techniques make available $$10^7 \bar{p}$$ and $$4 \times 10^9 e^+$$ for $$\bar{H}$$ experiments - an increase of over an order of magnitude. For the first time, $$\bar{p}$$ are observed to be centrifugally separated from the electrons that cool them, indicating a low-temperature, high-density $$\bar{p}$$ plasma. Determination of the $$\bar{p}$$ temperature is achieved through measurement of the $$\bar{p}$$ evaporation rate as their confining well is reduced, with corrections given by a particle-in-cell plasma simulation. New applications of electron and adiabatic cooling allow for the lossless reduction in $$\bar{p}$$ temperature from thousands of Kelvin to 3.5 K or colder, the lowest ever reported. The sum of the 20 trials performed in 2011 in which $$\bar{p}$$ and $$e^+$$ mix to form $$\bar{H}$$ in the presence of a magnetic quadrupole trap reveals a total of $$105 \pm 21$$ trapped $$\bar{H}$$, or $$5 \pm 1$$ per trial on average. This result paves the way towards the large numbers of simultaneously trapped $$\bar{H}$$ that will be necessary for laser spectroscopy. Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:10058466 Downloads of this work: