Search

The ASACUSA collaboration of CERN has recently irradiated antiprotonic helium atoms with two counter-propagating laser beams. This excited some non-linear two-photon transitions of the antiproton at the deep UV wavelengths λ = 139.8-197.0 nm. The counterpropagating geometry of the laser beams reduced the thermal Doppler broadening of the observed resonances. Their narrow spectral lines allowed the measurement of three transition frequencies with fractional precisions of 2.3-5 parts in 10. By comparing the results with three-body QED calculations, the antiproton-to-electron mass ratio was derived as 1836.1526736(23). [ABSTRACT FROM AUTHOR]

The ASACUSA collaboration has been making a path to realize high precision microwave spectroscopy of ground-state hyperfine transitions of antihydrogen atom in flight for stringent test of the CPT symmetry. For this purpose, an efficient extraction of a spin polarized antihydrogen beam is essential. In 2010, we have succeeded in synthesizing our first cold antihydrogen atoms employing a CUSP trap. The CUSP trap confines antiprotons and positrons simultaneously with its axially symmetric magnetic field to form antihydrogen atoms. It is expected that antihydrogen atoms in the low-field-seeking states are preferentially focused along the cusp magnetic field axis whereas those in the high-field-seeking states are defocused, resulting in the formation of a spin-polarized antihydrogen beam. [ABSTRACT FROM AUTHOR]

Quenching of individual metastable states of antiprotonic helium (p¯He+) in collisions with H2 and D2 in gas phase was studied using a laser-resonance method at CERN’s Antiproton Decelerator. The temperature dependence of the quenching cross-sections of the p¯He+ states (n,l) = (37, 34), (38, 35), and (38, 37) in the reactions [p¯He+](n,l) + H2 and [p¯He+](n,l) + D2 was investigated in the temperature range of 25–300 K. Significant quantum tunnelling effects were revealed at low temperatures and (n,l)-dependent reaction barriers were deduced, in good agreement with recent theoretical calculations. [Copyright &y& Elsevier]

A beam line for the transportation of slow antiprotons from a multiring electrode trap to an experimental chamber is described. The beam line is equipped with a three-stage differential pumping system in order to maintain a pressure lower than 1×10[SUP-12] Torr in the trap region while simultaneously having a pressure of around 1×10[SUP-6] Torr in the chamber. Tests have shown that 10[SUP5] positive ions per trapping cycle were successfully extracted at 250 eV from the trap positioned in a superconducting solenoid. The ions were then further transported through three small apertures to the target area located 3.5 m downstream of the trap. Results from the first delivery of a 250 eV antiproton beam are described. [ABSTRACT FROM AUTHOR]

Abstract: The design and properties of a new cryogenic set-up for laser–microwave–laser hyperfine structure spectroscopy of antiprotonic helium – an experiment performed at the CERN-Antiproton Decelerator (AD), Geneva, Switzerland – are described. Similar experiments for 4He have been performed at the AD for several years. Due to the usage of a liquid helium operated cryostat and therefore necessary refilling of coolants, a loss of up to 10% beamtime occurred. The decision was made to change the cooling system to a closed-circuit cryocooler. New hermetically sealed target cells with minimised 3He gas volume and different dimensions of the microwave resonator for measuring the 3He transitions were needed. A new set-up has been designed and tested at Stefan Meyer Institute in Vienna before being used for the 2009 and 2010 beamtimes at the AD. [Copyright &y& Elsevier]

Abstract: We report a determination of the antiproton magnetic moment, measured in a three-body system, independent of previous experiments. We present results from a systematic study of the hyperfine (HF) structure of antiprotonic helium where we have achieved a precision more than a factor of 10 better than our first measurement. A comparison between the experimental results and three-body quantum electrodynamic (QED) calculations leads to a new value for the antiproton magnetic moment , which agrees with the magnetic moment of the proton within . [Copyright &y& Elsevier]