Protonium production in ATHENA

NASA Astrophysics Data System (ADS)

Venturelli, L.; Amoretti, M.; Amsler, C.; Bonomi, G.; Carraro, C.; Cesar, C. L.; Charlton, M.; Doser, M.; Fontana, A.; Funakoshi, R.; Genova, P.; Hayano, R. S.; Jørgensen, L. V.; Kellerbauer, A.; Lagomarsino, V.; Landua, R.; Rizzini, E. Lodi; Macrì, M.; Madsen, N.; Manuzio, G.; Mitchard, D.; Montagna, P.; Posada, L. G.; Pruys, H.; Regenfus, C.; Rotondi, A.; Testera, G.; van der Werf, D. P.; Variola, A.; Yamazaki, Y.; Zurlo, N.; Athena Collaboration

2007-08-01

The ATHENA experiment at CERN, after producing cold antihydrogen atoms for the first time in 2002, has synthesised protonium atoms in vacuum at very low energies. Protonium, i.e. the antiproton-proton bound system, is of interest for testing fundamental physical theories. In the nested penning trap of the ATHENA apparatus protonium has been produced as result of a chemical reaction between an antiproton and the simplest matter molecule, H2+. The formed protonium atoms have kinetic energies in the range 40-700 meV and are metastable with mean lifetimes of the order of 1 μs. Our result shows that it will be possible to start measurements on protonium at low energy antiproton facilities, such as the AD at CERN or FLAIR at GSI.

Production of slow protonium in vacuum

NASA Astrophysics Data System (ADS)

Zurlo, N.; Rizzini, E. Lodi; Venturelli, L.; Amoretti, M.; Carraro, C.; Lagomarsino, V.; Macrì, M.; Manuzio, G.; Testera, G.; Variola, A.; Amsler, C.; Pruys, H.; Regenfus, C.; Bonomi, G.; Fontana, A.; Genova, P.; Montagna, P.; Rotondi, A.; Cesar, C. L.; Charlton, M.; Mitchard, D.; Jørgensen, L. V.; Madsen, N.; Van der Werf, D. P.; Doser, M.; Kellerbauer, A.; Landua, R.; Funakoshi, R.; Hayano, R. S.; Posada, L. G.; Yamazaki, Y.

We describe how protonium, the quasi-stable antiproton-proton bound system, has been synthesized following the interaction of antiprotons with the molecular ion H{2/+} in a nested Penning trap environment. From a careful analysis of the spatial distributions of antiproton annihilation events in the ATHENA experiment, evidence is presented for protonium production with sub-eV kinetic energies in states around n = 70, with iow angular momenta. This work provides a new two-body system for studies using laser spectroscopic techniques.

Production of slow protonium in vacuum

NASA Astrophysics Data System (ADS)

Zurlo, N.; Amoretti, M.; Amsler, C.; Bonomi, G.; Carraro, C.; Cesar, C. L.; Charlton, M.; Doser, M.; Fontana, A.; Funakoshi, R.; Genova, P.; Hayano, R. S.; Jørgensen, L. V.; Kellerbauer, A.; Lagomarsino, V.; Landua, R.; Lodi Rizzini, E.; Macrì, M.; Madsen, N.; Manuzio, G.; Mitchard, D.; Montagna, P.; Posada, L. G.; Pruys, H.; Regenfus, C.; Rotondi, A.; Testera, G.; van der Werf, D. P.; Variola, A.; Venturelli, L.; Yamazaki, Y.

2006-09-01

We descrbe how protonium, the quasi-stable antiproton-proton bound system, has been synthesized following the interaction of antiprotons with the molecular ion H_2^+ in a nested Penning trap environment. From a careful analysis of the spatial distributions of antiproton annihilation events in the ATHENA experiment, evidence is presented for protonium production with sub-eV kinetic energies in states around n = 70, with low angular momenta. This work provides a new two-body system for studies using laser spectroscopic techniques.

On the chemical reaction of matter with antimatter.

PubMed

Lodi Rizzini, Evandro; Venturelli, Luca; Zurlo, Nicola

2007-06-04

A chemical reaction between the building block antiatomic nucleus, the antiproton (p or H- in chemical notation), and the hydrogen molecular ion (H2+) has been observed by the ATHENA collaboration at CERN. The charged pair interact via the long-range Coulomb force in the environment of a Penning trap which is purpose-built to observe antiproton interactions. The net result of the very low energy collision of the pair is the creation of an antiproton-proton bound state, known as protonium (Pn), together with the liberation of a hydrogen atom. The Pn is formed in a highly excited, metastable, state with a lifetime against annihilation of around 1 micros. Effects are observed related to the temperature of the H2+ prior to the interaction, and this is discussed herein.

μ CF Study of D/T and H/D/T Mixtures in Homogeneous and Inhomogeneous Medium, and Comparison of Their Fusion Yields

NASA Astrophysics Data System (ADS)

Eskandari, M. R.; Faghihi, F.; Gheisari, R.

Muon reactivation coefficient are determined for muonic He (He = 42He = α , He = 23 He = h) for up to six (n = 1, 2, 3, ..., 6) states of formation and at temperature Tp = 100 eV and for various relative ion densities. In the next decade it may be possible to explore new conditions for further energy gain in muon catalyzed fusion system, μ CF, using nonuniform (temperature and density) plasma states. Here, we have considered a model for inhomogeneous μ CF for mixtures of D/T and H/D/T. Using coupled dynamical equations it is shown that the neutrons yield per muon injection, Yn (neutrons/muon), in the dt branch of an inhomogeneous H/D/T mixture is at least 2.24 times higher than similar homogeneous systems and this rate for a D/T mixture is 1.92. Also, we have compared the neutron yield in the dt branch of homogeneous D/T and H/D/T mixtures (temperature range T = 300-800 K, and density φ = 1 LHD). It is shown that Yn(D/T)/Yn(H/D/T) = 1.32, which is in good agreement with recently measured experimental values. In other words our calculations show that the addition of protonium to a D/T mixture leads to a significant decrease in the cycling rate for the physical conditions described herein.

Protonium Formation in Collisions of Antiprotons with Hydrogen Molecules

NASA Astrophysics Data System (ADS)

Cohen, James S.

1997-04-01

The first full-dynamics calculation of barp capture by the H2 molecule has been performed using the quasiclassical Kirschbaum-Wilets method with modifications for accurate treatment of the molecular structure. It had been speculated in calculations of heavy-negative-particle (μ^-) capture by the H atom(J. S. Cohen, R. L. Martin, and W. R. Wadt, Phys. Rev. A 27), 1821 (1983). that the capture cross section for the H2 molecule might be smaller than that for the atom at very low energies (based on the absence of adiabatic ionization for the molecule) but larger at higher energies (based on the molecule having two electrons and a higher ionization potential). This speculation seemed to be borne out by a diabatic-states calculation,(G. Ya. Korenman and V. P. Popov, AIP Conference Proceedings 181, p. 145 (1989).) which showed the two cross sections crossing at a center-of-mass energy of ~8 eV. However, both the qualitative argument and that calculation neglected the molecular vibrational and rotational dynamics. The present calculations show that the molecular degrees of freedom of the target are important and that the molecular capture cross section is always larger and extends to a higher collision energy ( ~80 eV vs. ~25 eV) than the atomic cross section. The distribution of n and l quantum numbers of the captured barp will also be presented.