1. The Development of Fluidised Powder Target Technology for a Neutrino Factory, Muon Collider or Superbeam Chris Densham Ottone Caretta, Peter Loveridge Rutherford Appleton Laboratory

2. Open jets Moving Segmented Pebble bed Monolithic Contained liquids SOLIDS LIQUIDS Looking for the ‘Goldilocks’ target technology

3. Open jets Moving Segmented Pebble bed Monolithic Contained liquids SOLIDS LIQUIDS Looking for the ‘Goldilocks’ target technology Too bendy?

4. Open jets Moving Segmented Pebble bed Monolithic Contained liquids SOLIDS LIQUIDS Looking for the ‘Goldilocks’ target technology Too bendy? Too complicated?

5. Open jets Moving Segmented Pebble bed Monolithic Contained liquids SOLIDS LIQUIDS Looking for the ‘Goldilocks’ target technology Too bendy? Too complicated? Too cavitated?

6. Open jets Moving Segmented Pebble bed Monolithic Contained liquids SOLIDS LIQUIDS Looking for the ‘Goldilocks’ target technology Too bendy? Too complicated? Too cavitated? Too messy?

7. Open jets Moving Segmented Pebble bed Monolithic Contained liquids SOLIDS LIQUIDS Fluidised powder Looking for the ‘Goldilocks’ target technology Not too solid and not too liquid: Just Right?

8. Fluidised powder target propaganda Shock waves –Material is already broken – intrinsically damage proof –No cavitation, splashing or jets as for liquids –high power densities can be absorbed without material damage –Shock waves constrained within material grains, c.f. sand bags used to absorb impact of bullets Heat transfer –High heat transfer both within bulk material and with pipe walls - so the bed can dissipate high energy densities, high total power, and multiple beam pulses Quasi-liquid –Target material continually reformed –Can be pumped away, cooled externally & re-circulated –Material easily replenished Other –Can exclude moving parts from beam interaction area –Low eddy currents i.e. low interaction with NF solenoid field –Fluidised beds/jets are a mature technology –Most issues of concern can be tested off-line -> experimental programme

9. Powder jet targets: some potential challenges 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 static powdered material Secondary heating of pipe walls –Choice of material? –How to cool? By powder material? Water spray?

10. Gravity fed powder heat exchangers

11. Pion+muon production for variable length 50% material fraction W vs 100% Hg r beam = r target = 0.5 cm NB increasing target radius is another knob to tweak Dotted line is Hg jet yield for 10 GeV beam using Study II optimum tilt, beam & target radii Acceptance criteria uses probability map to estimate acceptance through the cooling channel in (pT, pL) space. MARS calculation by John Back, Warwick University Length

12. Chris Densham NuFact10 Questions for the experimental programme Can a dense material such as tungsten powder be made to flow? Is tungsten powder fluidisable (it is much heavier than any material studied in the literature)? Is it possible to generate a useful fluidised powder geometry? Is it possible to convey it –in the dense phase? –in the lean phase? –In a stable mode? What solid fraction is it possible to achieve? (a typical loading fraction of 90% w/w solid to air ratio is not good enough!) How does a dense powder jet behave? Difficult to model bulk powder behaviour analytically Physical test programme underway: –First results March 2009

13. Powder Test rig at RAL Rig contains 100 kg Tungsten Particle size < 250 microns Discharge pipe length c.1 m Pipe diameter = 2 cm Typ. 2-4 bar (net) pneumatic driving pressure (max 10 bar)

14. Chris Densham NuFact10 1 1. Suction / Lift Summary of Operation

15. 1 2 1. Suction / Lift 2. Load Hopper Summary of Operation

16. 1 2 3 1. Suction / Lift 2. Load Hopper 3. Pressurise Hopper Summary of Operation

17. 1 2 3 4 1. Suction / Lift 2. Load Hopper 3. Pressurise Hopper 4. Powder Ejection and Observation

18. Test rig at RAL Total ~10,000 kg powder conveyed so far –> 100 ejection cycles –Equivalent to 20 mins continuous operation Batch mode operation –Tests individual handling processes before moving to a continuous flow loop

19. Chris Densham NuFact10 Le jet d’W Driving pressure = 2 bar Jet Velocity = 3.7 m/s Stable Jet Constant pressure in hopper throughout ejection Constant velocity over time Constant dimensions (with distance from nozzle and time) Jet material fraction = 42% ± 5% ~ bulk powder density at rest

20. Chris Densham NuFact10 Contained stable flow Contained unstable flow

21. Chris Densham NuFact10 Control Interface (GUI) Fully automated control system –Process control –Data Logging @ 20 Hz –Hard-wired safety interlocks Control System Interface (MATLAB) Experiment notes System indicator window Warning messages Emergency stop Suction settings Ejection settings

22. Particle Image Velocimetry velocity distribution required to determine bulk density Ottone Caretta, Oxford, Nov 09

23. Variations in the flow rate – typical 2bar ejection

24. Chris Densham NuFact10 Erosion Monitoring Expect rig lifetime to be limited by wear Wall thickness monitoring: –Dense-phase hopper / nozzle No damage –Lean-phase suction pipework Straight vertical lift to avoid erosion –Deflector plates So far so good Design to avoid erosion problems is critical –Lean phase optimisation ( ↓ u, ↑ ρ) –Avoid lean-phase bends –Operate without discharge valve –Replace deflector plate with powder/powder impact Ultrasonic Thickness Gauge Selected Material Hardness Values

25. Pneumatic Conveying Regimes Low Velocity High Velocity Increasing Driver Pressure

26. Pneumatic Conveying Regimes D. Lean Phase Low fraction of solid material High velocity = erosion! Used in vacuum recirculation line Low Velocity High Velocity Increasing Driver Pressure

27. Pneumatic Conveying Regimes D. Lean Phase Low fraction of solid material High velocity = erosion! Used in vacuum recirculation line Low Velocity High Velocity Increasing Driver Pressure C. Continuous Dense Phase Pipeline part full of material Stable continuous flow Intermediate velocity

28. Pneumatic Conveying Regimes C. Continuous Dense Phase D. Lean Phase 2.1 bar Run 57 Low fraction of solid material High velocity = erosion! Used in vacuum recirculation line Low Velocity High Velocity Increasing Driver Pressure

29. Pneumatic Conveying Regimes B. Discontinuous Dense Phase C. Continuous Dense Phase D. Lean Phase 2.1 bar Run 57 Low fraction of solid material High velocity = erosion! Used in vacuum recirculation line Low Velocity High Velocity Increasing Driver Pressure Pipeline almost full of material Unstable “plug flow” Intermediate velocity

30. Pneumatic Conveying Regimes 1.9 bar Run 56 B. Discontinuous Dense Phase C. Continuous Dense Phase D. Lean Phase 2.1 bar Run 57 Low fraction of solid material High velocity = erosion! Used in vacuum recirculation line Low Velocity High Velocity Increasing Driver Pressure

31. Chris Densham NuFact10 Pneumatic Conveying Regimes 1.9 bar Run 56 A. Solid Dense Phase B. Discontinuous Dense Phase C. Continuous Dense Phase D. Lean Phase Pipeline full of material, 50% v/v Low velocity Not yet achieved in our rig – further work 2.1 bar Run 57 Low fraction of solid material High velocity = erosion! Used in vacuum recirculation line Low Velocity High Velocity Increasing Driver Pressure

32. Schematic of powder target recirculation system for CW operation Gas lift (lean phase) Powder target pipe (dense phase) Gas lift receiver vessel Powder heat exchanger Pressurised powder hoppers Roots blower Gas heat exchanger Compressor Gas reservoir

33. Schematic of implementation as a Neutrino Factory target (similar for SuperBeam) Tungsten powder hopper Helium P beam Beam window Helium Beam window π Helium recirculation Lean phase lift

34. Flowability of tungsten powder –Excellent flow characteristics within pipes –Can form coherent, stable, dense open jet (c.10 kg/s for 2cm dia) –Density fraction of 42% ± 5% achieved ~ static bulk powder density Recirculation –Gas lift for tungsten powder has achieved 2.5 kg/s –NB this is equal to discharge rate for current baseline 1 cm diameter target at 10 m/s) Both contained and open powder jets are feasible A number of different flow regimes identified Design to mitigate wear issues is important for useful plant life – so far so good. No wear observed in any glass tubes used for discharge pipe tests Flowing powder target: interim conclusions

35. Optimise gas lift system Attempt to generate stable solid dense phase flow Investigate low-flow limit Carry out long term erosion tests and study mitigation Study heat transfer between pipe wall and powder Demonstrate magnetic fields/eddy currents are not a problem –Use of high field solenoid? Investigate active powder handling issues (cf mercury?) Demonstrate interaction with pulsed proton beam does not cause a problem –Application to use HiRadMat facility at CERN has been submitted Study low Z target material (e.g. graphite powder) for a 4 MW SuperBeam (SPL: NB the horn is another problem). Flowing powder target: future work