Lyman-alpha source for laser cooling antihydrogen
G. Gabrielse, B. Glowacz, D. Grzonka, C. D. Hamley, E. A. Hessels, N. Jones, G. Khatri, S. A. Lee, C. Meisenhelder, T. Morrison, E. Nottet, C. Rasor, S. Ronald, T. Skinner, C. H. Storry, E. Tardiff, D. Yost, D. Martinez Zambrano, M. Zieliński
abstract
We present a Lyman-alpha laser developed for cooling trapped antihydrogen. The system is based on a pulsed Ti:sapphire laser operating at 729 nm that is frequency doubled using an LBO crystal and then frequency tripled in a Kr/Ar gas cell. After frequency conversion, this system produces up to 5.7 mW of average power at the Lyman-alpha wavelength. This laser is part of the ATRAP experiment at the antiproton decelerator in CERN.
Electron-cooled accumulation of 4 × 10^9 positrons for production and storage of antihydrogen atoms
D. W. Fitzakerley, M. C. George, E. A. Hessels, T. D. G. Skinner, C. H. Storry, M. Weel, G. Gabrielse, C. D. Hamley, N. Jones, K. Marable, E. Tardiff, D. Grzonka, W. Oelert and M. Zieliński (ATRAP Collaboration)
abstract
Four billion positrons (e+) are accumulated in a Penning?Ioffe trap apparatus at 1.2 K and <6 × 10?17 Torr. This is the largest number of positrons ever held in a Penning trap. The e+ are cooled by collisions with trapped electrons (e?) in this first demonstration of using e? for efficient loading of e+ into a Penning trap. The combined low temperature and vacuum pressure provide an environment suitable for antihydrogen production, and long antimatter storage times, sufficient for high-precision tests of antimatter gravity and of CPT.
Large numbers of cold positronium atoms created in laser-selected Rydberg states using resonant charge exchange
R. McConnell, G. Gabrielse, W. S. Kolthammer, P. Richerme, A. Müllers, J. Walz, D. Grzonka, M. Zieliński, D. Fitzakerley, M. C. George, E. A. Hessels, C. H. Storry and M. Weel (ATRAP Collaboration)
abstract
Lasers are used to control the production of highly excited positronium atoms (Ps*). The laser light excites Cs atoms to Rydberg states that have a large cross section for resonant charge-exchange collisions with cold trapped positrons. For each trial with 30 million trapped positrons, more than 700 000 of the created Ps* have trajectories near the axis of the apparatus, and are detected using Stark ionization. This number of Ps* is 500 times higher than realized in an earlier proof-of-principle demonstration (2004 Phys. Lett. B 597 257). A second charge exchange of these near-axis Ps* with trapped antiprotons could be used to produce cold antihydrogen, and this antihydrogen production is expected to be increased by a similar factor.
Trapped Antihydrogen in Its Ground State
G. Gabrielse, R. Kalra, W. S. Kolthammer, R. McConnell, P. Richerme, D. Grzonka, W. Oelert, T. Sefzick, M. Zieliński, D. W. Fitzakerley, M. C. George, E. A. Hessels, C. H. Storry, M. Weel, A. Müllers, J. Walz
abstract
Antihydrogen atoms are confined in an Ioffe trap for 15 to 1000 seconds -- long enough to ensure that they reach their ground state. Though reproducibility challenges remain in making large numbers of cold antiprotons and positrons interact, 5 +/- 1 simultaneously-confined ground state atoms are produced and observed on average, substantially more than previously reported. Increases in the number of simultaneously trapped antithydrogen atoms are critical if laser-cooling of trapped antihydrogen is to be demonstrated, and spectroscopic studies at interesting levels of precision are to be carried out.
Pumped helium system for cooling positron and electron traps to 1.2K
J. Wrubel, G. Gabrielse, W. S. Kolthammer, P. Larochelle, R. McConell, P. Richerme, D. Grzonka, W. Oelert, T. Sefzick, M. Zieliński, J. S. Borbely, M. C. George, E. A. Hassels, C. H. Storry, M. Weel, A. Muellers, J. Walz, A. Speck
abstract
Extremely precise tests of fundamental particle symmetries should be possible via laser spectroscopy of trapped antihydrogen () atoms. atoms that can be trapped must have an energy in temperature units that is below 0.5 K?the energy depth of the deepest magnetic traps that can currently be constructed with high currents and superconducting technology. The number of atoms in a Boltzmann distribution with energies lower than this trap depth depends sharply upon the temperature of the thermal distribution. For example, ten times more atoms with energies low enough to be trapped are in a thermal distribution at a temperature of 1.2 K than for a temperature of 4.2 K. To date, atoms have only been produced within traps whose electrode temperature is 4.2 K or higher. A lower temperature apparatus is desirable if usable numbers of atoms that can be trapped are to eventually be produced. This report is about the pumped helium apparatus that cooled the trap electrodes of an apparatus to 1.2 K for the first time. Significant apparatus challenges include the need to cool a 0.8 m stack of 37 trap electrodes separated by only a mm from the substantial mass of a 4.2 K Ioffe trap and the substantial mass of a 4.2 K solenoid. Access to the interior of the cold electrodes must be maintained for antiprotons, positrons, electrons and lasers.
Adiabatic Cooling of Antiprotons
G. Gabrielse, W. S. Kolthammer, R. McConell, P. Richerme, R. Kalra, E. Novitski, D. Grzonka, W. Oelert, T. Sefzick,M. Zieliński, D. Fitzakerley, M. C. George, E. A. Hassels, C. H. Storry, M. Weel, A. Müllers, J. Walz
abstract
Adiabatic cooling is shown to be a simple and effective method to cool many charged particles in a trap to very low temperatures. Up to 3×106 antiprotons are cooled to 3.5 K - 10^3 times more cold antiprotons and a 3 times lower antiproton temperature than previously reported. A second cooling method cools antiproton plasmas via the synchrotron radiation of embedded e- (with many fewer e- than antiproton ) in preparation for adiabatic cooling. No antiprotons are lost during either process - a significant advantage for rare particles.
Centrifugal separation of antiprotons and electrons
G. Gabrielse, W. S. Kolthammer, R. McConell, P. Richerme, J. Wrubel, R. Kalra, E. Novitski, D. Grzonka, W. Oelert, T. Sefzick, M. Zieliński, J. S. Borbely, D. Fitzakerley, M. C. George, E. A. Hassels, C. H. Storry, M. Weel, A. Müllers, J. Walz, A. Speck
abstract
Centrifugal separation of antiprotons and electrons is observed, the first such demonstration with particles that cannot be laser cooled or optically imaged. The spatial separation takes place during the electron cooling of trapped antiprotons, the only method available to produce cryogenic antiprotons for precision tests of fundamental symmetries and for cold antihydrogen studies. The centrifugal separation suggests a new approach for isolating low energy antiprotons and for producing a controlled mixture of antiprotons and electrons.
