A. Deller

Experimental and computational study of the injection of antiprotons into a positron plasma for antihydrogen production

One of the goals of synthesizing and trapping antihydrogen is to study the validity of charge–parity–time symmetry through precision spectroscopy on the anti-atoms, but the trapping yield achieved in recent experiments must be significantly improved before this can be realized. Antihydrogen atoms are commonly produced by mixing antiprotons and positrons stored in a nested Penning-Malmberg trap, which was achieved in ALPHA by an autoresonant excitation of the antiprotons, injecting them into the positron plasma. In this work, a hybrid numerical model is developed to simulate antiproton and positron dynamics during the mixing process. The simulation is benchmarked against other numerical and analytic models, as well as experimental measurements. The autoresonant injection scheme and an alternative scheme are compared numerically over a range of plasma parameters which can be reached in current and upcoming antihydrogen experiments, and the latter scheme is seen to offer significant improvement in trapping y...

Manipulation of the magnetron orbit of a positron cloud in a Penning trap

We describe a simple and versatile method to manipulate the amplitude of the magnetron orbit of ions stored in a Penning trap, applied here to a cloud of low energy positrons. By applying a pulsed voltage to a split electrode in the trap, which is normally used for rotating wall compression of the particles, the size of the magnetron orbit can be changed at will. The modified orbit has been shown to be stable for many magnetron periods. The technique could find use in applications which require off-axis ejection of particles, for instance in the filling of arrays of traps for multicell positron storage.

Exciting positronium with a solid-state UV laser: the Doppler-broadened Lyman-αtransition

A tunable, pulsed laser was used to excite the Lyman-α transition (1S–2P) of positronium (Ps). The laser system has a large bandwidth of

Positronium emission and cooling in reflection and transmission from thin meso-structured silica films

\Delta \nu =225

Formation of positron-atom bound states in collisions between Rydberg Ps and neutral atoms

GHz at

A CF4 based positron trap

\lambda =243

A trap-based pulsed positron beam optimised for positronium laser spectroscopy.

nm, providing significant coverage of the Doppler-broadened, single-photon transition. The infra-red fundamental of a Nd:YAG laser was converted to ultraviolet by a series of solid-state, nonlinear processes, centred about an unseeded optical parametric oscillator, from which the bulk of the ultimate bandwidth derives. The Ps atoms were created by bombarding mesoporous silica with positrons, and the Doppler-width of the 1S–2P transition of the resulting ensemble was measured to be

Controlling Positronium Annihilation with Electric Fields

\Delta \nu =672\pm 43

Electron plasmas as a diagnostic tool for hyperfine spectroscopy of antihydrogen

GHz (equivalent to

Rydberg-Stark states of Positronium for atom optics

T\approx 300