Experiments with muons (μ+) and muonium atoms (μ+e-) offer several promising possibilities for testing fundamental symmetries of particle physics with high precision. Examples of such tests include the search for the muon electric dipole moment, measurement of the muon g - 2 and muonium laser spectroscopy. These experiments could benefit from a high-quality muon beam at low energy with small transverse size and high intensity.
At the Paul Scherrer Institute, a novel device (muCool device) that produces such a high quality muon beam is being developed, reducing the phase space of a standard μ+ beam by 10 orders of magnitude with 10-3 effciency. The muCool cooling scheme is based on stopping the muons in a cryogenic helium gas, where the they lose energy in collisions with the helium atoms. The stopped muons are then rapidly steered into a small spot using strong electric and magnetic fields in combination with gas density gradients. This process takes less than 10 μs, which is essential due to a short muon lifetime of 2.2 μs. Various aspects of this compression scheme have been demonstrated in the last few years. Excellent agreement of the measurements with GEANT4 simulations confirms that the predicted efficiency can be achieved.
In this seminar, I will explain the working principle of the muCool device and present the most recent measurements.