A Stationary Target for the CERN-Neutrino-Factory

As production target for Neutron Factories, free mercury jets with high axial velocity of about 20Â m/s are being studied. For the CERN-Neutrino-Factory proposal with a 4 MW beam power, but with a relatively large beam size at 2.2 GeV/c and pulsed at 75 Hz, maximum energy deposition densities of below 20 J/g and average power densities of about 1 kW/g are expected. Therefore a study has been made which discusses the feasibility and limits of a confined, stationary target cooled by a liquid. It is proposed to use solid spheres of high density material with diameters in the millimeter range. These spheres are confined inside a Titanium container and cooled by an efficient water circuit. Alternatively, low density liquid metal cooling could be used. Dynamic response, as pressure pulses and vibrations are greatly reduced by the small size of the target granules in combination with a relatively long beam pulse with a duration of 3.3 ms. The open issue of the lifetime of such as structure and its fatigue limit at a rate of 6.5 Mio. cycles per day must be assessed experimentally. Efforts should be invested in devising laboratory experiments simulating the beam conditions to optimize the design and to elucidate the limiting factors of such a target.