Frictional cooling: latest experimental results and first application

Frictional cooling - that is cooling a beam of very low-energy charged particles by moderation in matter and simultaneous acceleration in an electrostatic field - has been shown to be feasible during our experiments in 1994/1995 at PSI. As indicated by our previous closed-form and Monte-Carlo calculations we found a significant increase in spectral density and a decrease in the angular spread for a beam of negative muons. With the help of the cooled muons we were able to measure the diffusion times for pμ and dμ atoms in low-pressure (0.25 to 12 mbar) hydrogen gas. From this the mean kinetic energy of pμ atoms at the end of the cascade in 1 mbar hydrogen gas was determined to be (2.6 +/- 0.6) eV (preliminary value).