Ottone Caretta & Chris Densham Technology Business Unit Rutherford Appleton Laboratory A new idea for NuFact targets and beam dumps BENE Nov 06 – Frascati, IT

O.Caretta & C.Densham Solid targets Liquid targets Compact bed of particles Fluidised bed – jets targets Have to cope with the full amount of stress/deformation + retain its structural integrity Metamorphism + phase change Destructive shock/cycling of the material from liquid to solid targets

O.Caretta & C.Densham Example: liquid targets MERIT liquid mercury jet SNS spallation target Both are Very good but: If the liquid is confined-piped it has to cope with water hammer and cavitation Both have to cope with the unpleasant side effects of mercury (e.g. corrosion, radio chemistry) Work by Samuliak – McDonald - Simos

O.Caretta & C.Densham Example: solid targets T2K graphite target Very good but: Has to withstand shock waves and thermal cycling It is a static structure which has to cope with the full intensity of the beam maintaining its macroscopic integrity It is a low Z material (non ideal for NuFact) It probably has a limited life, then it has to be replaced! 750kW beam which deposits only 25-30kW in the target See presentation by Mike Fitton Work by Mike Fitton - RAL

O.Caretta & C.Densham Example: packed bed targets SLAC 400 kW electron beam dumps Bed of aluminium spheres ~1cm diameter in flowing water Very Good: a near hydrostatic stress field develops in the spheres so high energy can be absorbed before material damage The flowing fluid provides high heat transfer so the bed can cope with high energy densities However: The packed bed is stationary and still has to cope with the full intensity of the beam Has to withstand shock waves and thermal cycling It is more tolerant to damage It probably has a limited life, then it has to be replaced! Designed by Ditter Walz

O.Caretta & C.Densham Example: packed bed targets Accelerator Transmutation of Waste (ATW) ATW conceptual study Packed bed of tungsten particles in flowing helium Similar features as the previous work by Ammerman beam

O.Caretta & C.Densham Work by Pugnat & Sievers NuFact conceptual study for 1MW target Tantalum packed bed (2mm particles) in flowing He Example: packed bed targets NuFact target

O.Caretta & C.Densham The new idea: a fluidised bed/jet i.e. small particles circulating in a carrier fluid (e.g. He): Has the same advantages as the packed bed: –a near hydrostatic stress field develops in the particles so higher energies can be absorbed before material damage –The flowing fluid provides high heat transfer so the bed can cope with higher energy densities and total power (and perhaps more than one beam pulse) Plus some more: –Can have very high Z and density –Can be shaped as required –Can be easily renewed/replenished as the particles wear or get damaged –Will absorb only the designed amount of energy and then flow out of the scene to get cooled and replenished (if necessary) –It carries both the advantages of the solid phase (high density) and of the liquid phase (metamorphic, pumpable, replenishable)

O.Caretta & C.Densham Gas flow Floating particulate bed Centrifugal separators Typical fluidised bed plant

O.Caretta & C.Densham Examples of fluidised bed designs. Very effective for thermo-chemical reaction Very effective heat transfer: Particles bouncing on the coils of a H.E. transfer heat by conduction

O.Caretta & C.Densham Example of heat transfer in a fluidised bed Heat transfer depends on the gas velocity and particulate size ~350 [W/m^2]

O.Caretta & C.Densham Fluidised dump/target Gas flow Particles flow beam NB target station needs vacuum entry & exit windows, but these can be reasonably remote from the target (see talk by Matt Rooney)

O.Caretta & C.Densham Example: fluidised jet of particles in carrier gas A Fluidised jet of tungsten or tantalum particles in He could be used as a neutrino factory target –It could have high Z + high volume density –Can be effectively removed from the solenoid field hence reducing the pion reabsorption –Can be replenished as particles wear out –Particles can be easily cooled (in an external fluidised bed)

O.Caretta & C.Densham Fluidised pipe flow vs injection High concentration homogeneous particulate flow is difficult to maintain over long distances However the solid phase can be effectively collected in a conveyor and injected at/near the point of use in high concentrations (5:1 to 90:1 solid/gas) Very similar to the jet produced by a grit blasting device: it is all standard technology!

O.Caretta & C.Densham Particle jet as a NuFact target solenoid Particles jet He flow beam Pion shower

O.Caretta & C.Densham Summary Combines the advantages of the solid target with those of the liquid target Solid displacement without moving parts Shock waves constrained within the material (no cavitation, no splashing) Highly effective cooling of the target material Favourable material geometry for the stress waves Target easily replenished Nothing else on the beam line apart from the target material

O.Caretta & C.Densham Proposed future work Evaluation of the energy deposition and pion shower for the fluidised jet/bed configuration Evaluation of the thermal mechanical stress on the particles Analysis of the thermal mechanical stresses on the beam window (investigate options to reduce power density on the window) Optimisation of the target/plant layout (e.g. injector nozzle, jet deflector/ capture, etc.) Any comments and suggestions are welcome