B. Juhász

Transport beam line for ultraslow monoenergetic antiprotons

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 1×10−12u200aTorr in the trap region while simultaneously having a pressure of around 1×10−6u200aTorr in the chamber. Tests have shown that 105 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.

Systematic study of the decay rates of antiprotonic helium states

A systematic study of the decay rates of antiprotonic helium (p{sup 4}He{sup +} and p{sup 3}He{sup +}) at CERN Antiproton Decelerator has been made by a laser spectroscopic method. The decay rates of some of its short-lived states, namely those for which the Auger rates {gamma}{sub A} are much larger than their radiative decay rates ({gamma}{sub rad}{approx}1 {mu}s{sup -1}), were determined from the time distributions of the antiproton annihilation signals induced by laser beams, and the widths of the atomic resonance lines. The magnitude of the decay rates, especially their relation with the transition multipolarity, is discussed and compared with theoretical calculations.

Measurement of the ground‐state hyperfine structure of antihydrogen

The ASACUSA collaboration at CERN‐AD has recently submitted a proposal to measure the hyperfine splitting of the ground state of antihydrogen in an atomic beam apparatus [ASACUSA proposal addendum, CERN/SPSC 2005‐002, SPSC P‐307 Add.1 (2005)]. The apparatus consists of two sextupoles for spin selection and analysis, and a microwave cavity to flip the spin. This method has the advantage that antihydrogen atoms of temperatures up to 150 K ‘evaporating’ from a formation region can be used. Numerical simulations show that such an experiment is feasible if ∼100 antihydrogen atoms per second can be produced in the ground state, and that an accuracy of better than 10−6 can be reached. This measurement will be a precise test of the CPT invariance.

Effects of impurity molecules on the lifetime of antiprotonic helium atoms

Abstract Quenching of metastable antiprotonic helium atoms in collisions with hydrogen and deuterium molecules has been studied using laser spectroscopy at CERN’s antiproton decelerator. The temperature dependence of the quenching cross sections of the antiprotonic states ( n , l )=(37,34), (38,35) and (38,37) has been investigated and a deviation from the Arrhenius law was found at low temperatures. In case of the state (38,37) with deuterium, detailed measurements revealed that the quenching cross section levels off at low temperatures indicating a strong quantum tunneling effect.

Precise laser spectroscopy of the antiprotonic helium atom and CPT test on antiproton mass and charge

Abstract We have measured twelve transition frequencies of the antiprotonic helium atom (pHe + ) with precisions of 0.1–0.2 ppm using a laser spectroscopic method. The agreement between the experiment and theories was so good that we can put a limit on the proton-antiproton mass (or charge) difference. The new limit is expected to be much smaller than the already published value, 60 ppb (6 × 10 −8 ).