Frictional cooling: Experimental results

The classical methods used in beam cooling are hard to be adapted for a bea m of short-lived elementary particles. A novel method, the so-called fricti onal cooling - that is cooling a beam of low-energy charged particles by mo deration in matter and acceleration in an electrostatic field - has been sh own to be feasible. In our experiments performed in 1994/1995 a beam of sho rt-lived particles was cooled for the first time ever. Utilizing frictional cooling on a beam of slow negative muons we observed increase in phase spa ce density by about one order of magnitude.