4 mois (Mars 2020 - Juin 2020)

Positronium laser cooling


The student will take part in the development of a laser system generating trains of short pulses spanning 100 ns with a
strong linear chirp specially designed for positronium laser cooling. The student will run simulations to interpret and
optimize the process of positronium laser cooling. Positronium laser cooling experiments are based at CERN. The
internship will be either based at CERN (Geneva, Switzerland) with the AEgIS collaboration or at NTNU (Trondheim,
Norway). The supervisor will be also performed by Antoine Camper (antoine.camper@cern.ch):

Detailed summary:
Positronium (Ps) is the bound state of an electron with its antimatter counterpart, a positron. This exotic matter-
antimatter system has recently attracted a renewed attention with the development of intense pulsed sources of Ps
opening the way to applications such as antihydrogen production, CPT test through refined spectroscopy or antimatter
wave interferometry. The velocity of the Ps atoms is critical for these applications and the AEgIS collaboration came
up with a program for laser cooling of Ps. In contrast with alkaline atoms, the 142 ns ortho-Ps lifetime limits the
interaction between the atoms and the laser, so that laser cooling must be done in a few hundreds of nanoseconds. The
1s → 2p transition used for cooling is driven with a 243 nm laser meaning a strong recoil in comparison to more
traditional laser cooled atoms. The excitation lifetime of the 2p state is ~3ns which means the coherence between the
different quantum states can be neglected and no optical molasse is formed. All of this makes Ps laser cooling
challenging and sets it apart from more classical laser cooling experiments.The student will be involved in the development and implementation of a laser system for Ps laser cooling and will
perform simulations of the laser-atoms interaction to properly model the cooling process. Developments such as using
the cooling laser system in combination with a narrow band titanium sapphire laser to perform precise spectroscopy of
Ps Rydberg levels on cold atoms will be investigated as a development for a potential PhD.

[1] S. Mariazzi, et al., Phys. Rev. Lett. 104, 243401 (2010)
[2] S. Aghion, et al. Phys. Rev. A 98, 013402 (2018)
[3] D. B. Cassidy Eur. Phys. J. D 72, 53 (2018)

Daniel COMPARAT - Contacter
Laboratoire Aimé cotton, bât 221, Campus d'ORSAY, 91405 Orsay Cedex.