BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Solid target studies in UK for T2K and for a neutrino factory JRJ Bennett, S Brooks, R. Brownsword, O Caretta, CJ Densham, R Edgecock, MD Fitton, VB Francis, S Gray, A McFarland, M Rooney, G Skoro* and D Wilkins Underlined are those who have given talks at BENE06 Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, UK Except * Sheffield University, UK

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Solid target studies in UK for T2K and for a neutrino factory Partial summary of BENE06 presentations: T2K target station beam entry window Matt Rooney Design and Computational Fluid Dynamic analysis of the T2K Target Mike Fitton Shock wave experiments for T2K and Nufact target materials. Chris Densham Fluidised beds: a new idea for a neutrino factory target Otto Caretta

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory T2K Secondary Beam Line DV TS BD Beam Dump(BD) graphite core in helium vessel Target station (TS) Target & horns in helium vessel Helium vessel and iron shields cooled by water Decay Volume (DV) 94m long helium vessel cooled by water 6m thick concrete shield ‘280 m’ neutrino monitor 50 GeV PS ring Primary beam line Fast extraction Kamioka

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory T2K Target area Inner iron shields Inner concrete shields Support structure = Helium vessel (being constructed by Mitsui Ship. Co.) BaffleTarget and 1st horns 2nd horns 3rd horns Beam window

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory The T2K Beam Window Matt Rooney

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Beam Window Assembly Window Overview - Double skinned partial hemispheres, 0.3 mm thick. - Helium cooling through annulus. - Ti-6Al-4V. - Inflatable pillow seal on either side. - Inserted and removed remotely from above.

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Helium cooling of beam window He in He out Upstream Annulus Downstream Helium velocity ≈ 5 m/s Heat transfer coefficient ≈ 150 W/m2K

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Stress Waves: effect of 8 bunches/beam spill Stress wave development in 0.6 mm constant thickness hemispherical window over first 2 microbunches.

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory 0.62 mm thick Ti-6Al-4V window - Constructive Interference between bunches

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory 0.3 mm thick Ti-6Al-4V window - Destructive interference between bunches

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Important lesson: thicker is not always stronger! With a pulsed proton beam, window and target geometry can greatly affect the magnitude of stress. Be careful to check dynamic stress when changing beam parameters or target and window geometry!

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Design and Computational Fluid Dynamic analysis of the T2K Target Mike Fitton

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory RAL target design in the 1 st Horn

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Helium cooling flow path Matt Rooney’s initial calculations suggest this window is ok for pressure and shock. Inlet Manifold Outlet Manifold Flow turns 180° at downstream window

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Animation of flow

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Velocity Streamlines Current design Previous design iteration Optimised for uniform flow

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Velocity profile at downstream window 30 GeV, Hz, 750 kW Radiation damaged graphite Optimisation for pressure drop and window cooling Original Concept Current RAL Design Pressure drop unacceptable No downstream window

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory 30 GeV, Hz, 750 kW Radiation damaged graphite (20 [W/m.K]) Mass flow rate = 32 g/s Steady state target temperature Maximum temperature = 1009˚K = 736˚C

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Radiation Damage of Graphite For a radiation damaged target a thermal conductivity of 20 [W/m.K] is used (approx 4 times lower than new graphite at 1000°K)

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory T2K graphite target stress waves Max Von Mises Stress:Ansys – 7MPa LS-Dyna – 8Mpa Max Longitudinal Stress:Ansys – 8.5MPa LS-Dyna – 10MPa AnsysLS-Dyna

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Shock wave experiments for T2K and Nufact target material Results from ‘Shock Tests on Tantalum and Tungsten’ - presented by Roger Bennett at Nufact06

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Shock wave experiment at RAL Pulsed ohmic-heating of wires to replicate pulsed proton beam induced shock waves in materials - using ISIS kicker magnet power supply current pulse Material test wire

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory LS-Dyna calculations for shock-heating of different graphite wire radii G.Skoro, Sheffield University

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Vertical Section through the Wire Test Apparatus Current Inner conductor of co-axial insulator feed-through. Stainless steel split sphere Copper “nut” Current Two graphite (copper) wedges Spring clips Fixed connection Sliding connection Test wire: Graphite (T2K) or Tungsten (nufact)

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Some Results of 0.5 mm diameter wire tests and ‘equivalent’ nufact target parameters Beam Power MW 4.2x10 6 +PLUS+ >9.0x10 6 >1.6x10 6 >3.4x x10 6 No. of pulses to failure Max. Temp K Not broken. Top graphite connector failed Stuck to top Cu connector Broke when increased to 7200A (2200K) Tungsten Tantalum is not a very good material – too weak at high temperatures Tantalum Target dia cm Rep Rate Hz Pulse Temp. K Pulse Current A Lngth cm Material “Equivalent Target”: This shows the equivalent beam power (MW) and target radius (cm) in a real target for the same stress in the test wire. Assumes a parabolic beam distribution and 4 micro-pulses per macro-pulse of 60  s. Equivalent Target

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Velocity Interferometry (VISAR) : to measure shock waves on material surface Laser Frequency ω Sample Velocity u(t) Fixed mirror Beamsplitter Etalon Length h Refractive index n Detector Fixed mirror

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory  Tungsten appears to be a candidate for a neutrino factory solid target and should last for several years.  In this time it will receive ~10-20 dpa. This is similar to the 12 dpa suffered by the ISIS tungsten target with no problems.  Tantalum is too weak at high temperatures to withstand the stress waves.

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory A new idea for NuFact targets and beam dumps Otto Caretta

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Work by Pugnat & Sievers NuFact conceptual study for 1MW target Tantalum packed bed (2mm particles) in flowing He Already proposed by P. Sievers (CERN): packed bed targets NuFact target

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory The new idea: a fluidised bed/jet 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) A fluidised bed/jet of sand particlesof

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory 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!

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory A fluidised bed/jet: 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)

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory Particle jet as a NuFact target solenoid Particles jet He flow beam Pion shower

BENE/CARE Frascati November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory BENE target work: the future