1. A powder jet target for a Neutrino Factory Ottone Caretta, Chris Densham (RAL), Tom Davies (Exeter University), Richard Woods (Gericke Ltd)

2. Chris Densham UKNF 3 rd Oct 2007 Open jets Target technology problems: Power dissipation Radiation damage Shock waves/ thermal stress MovingSegmentedMonolithic Contained liquids Increasing power SOLIDS LIQUIDS Cooling Lubrication / tribology Reliability Shock waves, Cavitation Corrosion Radiochemistry Splashing, radiochemistry, corrosion Challenges:

3. Chris Densham UKNF 3 rd Oct 2007 T2K at JPARC Next Generation Long Baseline Neutrino Oscillation Experiment

4. Chris Densham UKNF 3 rd Oct 2007 Solid T2K target supported within the 1 st Horn Helium cooling pipe

5. Chris Densham UKNF 3 rd Oct 2007 Graphite to titanium diffusion bond Graphite-to-graphite bond Flow turns 180° at downstream window Inlet manifold Outlet manifold Upstream Window T2K Target Design: Helium cooling path

6. Chris Densham UKNF 3 rd Oct 2007 Pressures (gauge) Pressure drop = 0.792 bar Velocity Streamlines Maximum velocity = 398 m/s

7. Chris Densham UKNF 3 rd Oct 2007 Options for T2K upgrade to Superbeam Window: should be OK if increased power is gained by increasing rep rate. Target: Static target difficult beyond 1 MW beam power – problems include: –Power dissipation –Thermal stress –Radiation damage –High helium flow rate, large pressure drops Target: expect to replace target increasingly often as beam power increases New target technology seems necessary

8. Chris Densham UKNF 3 rd Oct 2007 Open jets Is there a ‘missing link’ target technology? SOLIDS LIQUIDS Monolithic Powder jets Contained liquids Segmented

9. Chris Densham UKNF 3 rd Oct 2007 Examples: fluidised jets of particles in a carrier gas

10. Chris Densham UKNF 3 rd Oct 2007 Different fluidising technologies www.claudiuspeters.com

11. Chris Densham UKNF 3 rd Oct 2007 Powder jet targets: some potential advantages Shock waves –a near hydrostatic stress field develops in the particles so high energies can be absorbed before material damage –Shock waves constrained within material – no splashing or jets as for liquids –Material is already broken Heat transfer –A flowing powder provides high heat transfer opportunities so the bed can dissipate high energy densities and total power (and perhaps more than one beam pulse) –External cooling Solid vs liquid? –Carries some of the advantages of both the solid phase and of the liquid phase: metamorphic, can be shaped to suit Pumpable replenishable - as powder wears out or gets damaged

12. Chris Densham UKNF 3 rd Oct 2007 Powder jet targets: some potential difficulties Erosion of material surfaces, e.g. nozzles Activated dust on circuit walls (no worse than e.g. liquid mercury?) Activation of carrier gas circuit Achieving high material density – typically 50% material packing fraction for a powdered material

13. Chris Densham UKNF 3 rd Oct 2007 Some existing solutions to the erosion problem Turbulent energy dissipation Specially designed gravity fed heat exchangers

14. Chris Densham UKNF 3 rd Oct 2007 Could a flowing powder or powder jet be a useful target technology? For a T2K upgrade or another Superbeam e.g. SPL Obvious material for T2K would be graphite powder But 50% material would reduce pion yield How about titanium powder? Density of titanium powder may be similar to solid graphite, ie 50% ρ Ti ≈ ρ graphite For a Neutrino Factory target Tungsten powder obvious candidate –> the rest of this talk

15. Chris Densham UKNF 3 rd Oct 2007 Schematic outline of a powder jet as a NuFact target solenoid W powder jet He flow beam Pion shower

16. Chris Densham UKNF 3 rd Oct 2007 Neutrino Factory Study II Target station layout W powder jet target roughly compatible with mercury jet target station layout – replace Hg pool with W powder receiver

17. Chris Densham UKNF 3 rd Oct 2007 Neutrino Factory Study II Target station layout W powder jet target roughly compatible with mercury jet target station layout – replace Hg pool with W powder receiver W powder

18. AIR LIFT POWDER JET NOZZLE RECEIVER POWDER COOLER GAS COOLER EXHAUSTER COMPRESSOR GAS POWDER FLUIDISED PRODUCT Powder jet target plant - outline layout SOLENOID BORE MIMIC

19. Chris Densham UKNF 3 rd Oct 2007 AIR/PRESSURE IN POWDER IN JET GENERATION AIR EXTRACTION/ VACUUM LIFT DENSE MATERIAL FLOW ~1m AUXILIARY AIR INPUT (NOT NEEDED) Powder jet prototype test plant - layout used in experiment AIR IN

20. Chris Densham UKNF 3 rd Oct 2007 The first day’s experiment 18 th July 2007 Tungsten powder < 250 µm particle size Discharge pipe length = 1 m Pipe diameter = 2 cm 3.9 bar (net) pneumatic driving pressure

21. Chris Densham UKNF 3 rd Oct 2007 The first day’s experiment 18 th July 2007 Tungsten powder < 250 µm particle size Discharge pipe length = 1 m Pipe diameter = 2 cm 3.9 bar (net) pneumatic driving pressure Approx. 10 m/s and c. 18% material by volume achieved

22. Chris Densham UKNF 3 rd Oct 2007 The second day’s experiment 30 th August 2007 Tungsten powder < 250 µm particle size Discharge pipe length = 1 m Pipe diameter = 2 cm 3.9 bar (net) pneumatic driving pressure Vacuum lift to recirculate powder Co-axial return air flow at entry of jet into mimic of solenoid bore

23. Chris Densham UKNF 3 rd Oct 2007 The second day’s results: (Thanks to EPSRC Intrument Loan Pool for use of a high speed video camera ) 2 cm 30 cm

24. Chris Densham UKNF 3 rd Oct 2007 P 0 = 4.9 bar (abs) P 1 = 1 bar (abs) Initial bulk density = 8660 kg/m 3 = 45 % W (by volume) Jet bulk density (approx. results): ~ 5000 kg/m 3 ~ 25 % W by vol. ( ~ 2.5 x graphite density) Jet velocity = 7-15 m/s (100 kg in 9 seconds) Tungsten powder jet – second day’s results

25. Chris Densham UKNF 3 rd Oct 2007 NB 1: Calculation is for 10 GeV protons NB 2: Calculation is for total yield from target ie capture losses excluded MARS calculation of muon and pion yield from (i)solid W and (ii)50% density W by John Back, Warwick University

26. Chris Densham UKNF 3 rd Oct 2007 Improve bulk density of jet (-> 45% by volume?) –18% -> 25% achieved by co-axial air flow - DONE –By changing discharge pipe length? –By incorporating porous (sintered) material into discharge pipe? –By use of a nozzle? Demonstrate shock waves are not a problem –Possibility to use test facility planned at ISOLDE for shock wave experiment on a powder sample – as for the mercury thimble experiment (Jacques Lettry) Demonstrate magnetic fields/eddy currents are not a problem –Use of high field solenoid (post MERIT – collaboration with CERN + Harold Kirk?) Powder jet: next stages

27. Chris Densham UKNF 3 rd Oct 2007 Questions (mine) and requests Is a powder jet target of maximum density < 50% volume density an interesting or serious contender for either: –A Superbeam (e.g. graphite or Ti powder for T2K upgrade?) –A Neutrino Factory (e.g. W)? –NB multiple bunches interacting with same material should be OK If so, what are roughly optimal parameters for e.g. W powder NuFact target? MARS help requested. Could a contained pipe flow be used? –Necessary for T2K Superbeam, possible for NuFact? –(NB problems of window and 2ndary heating of pipe to be addressed)

28. Chris Densham UKNF 3 rd Oct 2007 Questions (yours)?

29. Chris Densham UKNF 3 rd Oct 2007 Some porous sintered materials used in fluidised bed technologies