[en] Full text: Proton beams with an average beam power of several MW are needed to produce the high secondary particle flux required by future accelerator centres like neutrino factories or neutron spallation sources. In such scenarios, the secondary beams are produced via conversion targets and the high power involved imposes the need for advanced target concepts. The use of liquid metal is a natural solution to the stresses and fatigue, induced by the proton beam, that eventually lead to the destruction of most solid targets. A liquid jet would provide a 'new' target for each proton pulse if the material disrupted by the proton beam can be evacuated within the proton pulse interval. Such a target configuration is presently considered for the pion production target of a neutrino superbeam or a neutrino factory. We present experimental results on the impact of proton beam pulses on free-surface liquid metal targets. These tests were performed at the ISOLDE facility at CERN. (author)