A Stationary Target for the CERN-Neutrino-Factory

As production target for Neutrino Factories,free mercury jets with high axial velocity of about 20 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 50 Hz ,maximum energy deposition densities of below 20 J /g and average power densities of about 1 kW /g are expected in the target.Therefore a study has been made which discusses the feasibility and limits of a stationary target.It is proposed to use densely packed solid spheres of heavy material and with diameters in the millimeter range.These spheres are con fined inside a Titanium container and cooled by an e fficient water circuit or possibly by He-gas.Dynamic response,as pressure pulses and vibrations are greatly reduced in the small target granules due to relatively long beam bursts,each with a duration of 3.3 s .The encouraging results achieved in this assessment justify to pursue further experimental tests,in particular of the cooling of the target,its lifetime under repetitive thermal cycles (4.3 Mio/day) and of radiation damage,to validate this proposal.It is expected that the lifetime of this target will be adequate for the operation of the CERN- Neutrino-Factory,at least over its initial phase below 4 MW beam power.