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We describe the experimental production of a beam of 23S1 positronium (Ps) atoms obtained from charge-exchange collisions between a positron beam and Xe held in a gas cell. The angular divergence of the emitted Ps beam was recorded using two position sensitive detectors located at different distances from the gas cell. The fraction of the Ps beam produced in the 23S1 level was measured via the change in the Ps count rate after driving the 23S1 → 23P2 transition with microwave radiation; with optimal experimental parameters, we estimate that up to 10% of the Ps beam is formed in the 23S1 state. The measured properties of the beam were used to evaluate the feasibility of using the system for precision spectroscopy of the n = 2 Ps fine structure using Ramsey interferometry. [ABSTRACT FROM AUTHOR]

We describe an experimental arrangement suitable for performing microwave spectroscopy measurements of the positronium (Ps) n = 2 fine structure using Ramsey interferometry. Simulations are presented concerning the production of energetic 2 3 S 1 Ps atoms from a Xe gas cell, and their subsequent interactions with a pair of waveguides in which coherent microwave radiation fields are applied. We conclude that for realistic experimental parameters, optimized using a Monte Carlo simulation, a gas cell length of 10 cm with a gas pressure of 0.5 Pa and a positron beam energy of 40 eV, count rates on the order of 50 Hz should be possible. [ABSTRACT FROM AUTHOR]

We describe a pulsed positron beam that is optimised for positronium (Ps) laser-spectroscopy experiments. The system is based on a two-stage Surko-type buffer gas trap that produces 4 ns wide pulses containing up to 5 x 105 positrons at a rate of 0.5-10 Hz. By implanting positrons from the trap into a suitable target material, a dilute positronium gas with an initial density of the order of 107 cm-3 is created in vacuum. This is then probed with pulsed (ns) laser systems, where various Ps-laser interactions have been observed via changes in Ps annihilation rates using a fast gamma ray detector. We demonstrate the capabilities of the apparatus and detection methodology via the observation of Rydberg positronium atoms with principal quantum numbers ranging from 11 to 22 and the Stark broadening of the n = 2 → 11 transition in electric fields. [ABSTRACT FROM AUTHOR]

A High Voltage Engineering K-4000 Van de Graaff ion accelerator has been acquired by Washington State University. This accelerator will be used to create a positron source through the 12C(d, n)13N reaction. The accelerator is capable of accelerating protons or deuterons up to 4 MeV with a maximum beam current between 200 and 300 μA. During normal operation, a 3 MeV deuteron beam will impinge on a diamond or graphite target producing ∼3.3 Ci of 13N from which a ∼1×107 s−1 monoenergetic positron beam will be created. In addition to creating positrons, the source will also emit a large number on neutrons (∼1.2×1011 s−1), producing a serious radiation hazard. The development of this 13N based positron beam is discussed including the expected positron yield and radiation shielding requirements. [Copyright &y& Elsevier]