1. Chris Densham Figures of Merit for target design for neutrons, neutrinos… Chris Densham Rutherford Appleton Laboratory

2. Chris Densham End-to-end simulations of accelerator driven facilities highly sophisticated & complex –Computationally expensive – e.g. genetic algorithm –‘Black box’ type output –Can be difficult to identify ‘design guidelines’ –‘Listen to the robot’ for the answer Useful to have a tool that (ref R.Zwaska) : –Can factorise problems – orthogonal to genetic algorithm –Is readily understood –Can apply to a distribution Also useful to have a tool to compare reliability (materials or engineering issues) Motivations for ‘Figures of Merit’

3. 3 Presentation name Neutron Economy at SNS 1.4 MW SNS produces:2 ×10 17 n/s Thermal neutrons at beamline start:2×10 12 n/s Neutrons at sample position (white):2×10 11 n/s Neutrons at sample (chopped):2×10 10 n/s Neutrons scattered:2×10 8 n/s Neutrons counted:5×10 7 n/s Neutron counted/Neutrons produced:3×10 -10 F. X. Gallmeier

4. Figures of Merit for Physics & Engineering? Chris Densham 29 February 20164

5. ISIS First Target Station Upgrade Project To upgrade key elements of TS1 including moderators, reflectors and target infrastructure Aims to achieve a factor of 2 or more increase in neutronic performance for a modest cost. Use modern software and analysis techniques to improve neutronic efficiency without increasing the beam power. Develop a more efficient spallation reflector, moderator, target system. The ISIS First Target Station Target, moderators and reflector assembly

6. 6 Ambient Water Methane Hydrogen Existing TS1 target & moderator assembly protons ISIS TS1 Upgrade Maximise neutronic output Optimise beam power (~200 kW seems just fine) ‒ Make more compact ‒ Less neutron-absorbing material Water flow lines Temperatures Tungsten

7. Chris Densham Increasing Beam Power – Neutronics Stuart Ansell and Goran Skoro modelled neutronic gain as a function of beam current for several target types: Higher beam power => more plates required => more water in target => longer neutron pulse width

8. Chris Densham Neutrinos: LBNF/DUNE Experiment Muon neutrinos/antineutrinos generated by 1.2 – 2.4 MW proton beam at Fermilab Long baseline -> large matter effects (unlike T2K, Hyper-K) –Measurement of neutrino mass hierarchy On-axis, wide-band beam (wide range of neutrino energies ~ few GeV) –Measurement of different oscillation rates for νs and anti-νs –Unfold CP-violation from matter effects through E dependence –Can capture both 1 st and 2 nd oscillation maxima 8 1300 km

9. Chris Densham Laura Fields

10. Chris Densham Laura Fields

11. Chris Densham

12. Results of optimisation 12

13. Chris Densham High Z cooling tube or downstream plug? High z plug downstream of the target and/or high z target outer tube Increase pion yield relative to a 2 interaction length graphite target. Graphite cylinder inside a High-Z tube gives best increase in yield A comparative Figure of Merit would be useful to compare & optimise different designs c/o Mary Bishai

14. Chris Densham ‘Figure of Merit’ for LBNF FoM=(R Zwaska)N i = Number of pions in bins from 1.5 GeV < E < 12 GeV for p t < 0.4 GeV Useful indication of physics performance to inform engineering studies Weights higher energy (more interesting) pions to balance drop in production at higher energies NB needs to be modified to take into account 2 nd oscillation max at c.1 GeV FLUKA simulations T. Davenne, O. Caretta

15. Chris Densham Figure of Merit Comparison for different target and beam sizes FLUKA simulations Target radius

16. Target exchange system T2K Target & horn Helium cooled graphite rod Design beam power: 750 kW Beam power so far >350 kW σ = c. 4.2 mm 3% beam power deposited in target 1 st target & horn replaced after 4 years, 6.5e20 p.o.t. 2 nd target repaired after 5 e20 p.o.t. π π p

17. Effect of pulsed beam on T2K target Inertial ‘violin modes’ Stress distribution after off-centre beam spill Radial stress waves – on centre beam spill 8 MPa 0.5 µs beam spill p

18. Effects of pulsed beams: NuMI target Autopsy of water-cooled NuMI target NT-03 (photo courtesy of V. Sidarov) Possible explanation: high tensile stress after beam pulse (damage may also have occurred during removal of target tube)

19. Fast neutron radiation damage data for graphite (IG 110)

20. Radiation damage – any chance of a FoM? C.A. English (2011)

21. Figures of Merit for target/collimator materials (proposed by A. Bertarelli, CERN) Chris Densham 29 February 201621

22. Limitations of target technologies Peripherally cooled monolith Flowing or rotating targets Segmented

23. Chris Densham Particle Production Target ‘Optimum’ Performance For particle flux – small beam σ is favoured –A ‘Figure of Merit’ can indicate physics performance For target lifetime – bigger is better. –Lower power density – lower temperatures, lower stresses –Lower radiation damage rate –Lower amplitude ‘violin’ modes (and lower stresses) –Need another Figure of Merit for target engineering issues For integrated particle flux, need to take both these factors into account –E.g. How to achieve best physics performance possible for a target lifetime of a minimum of 1 year? –Answer will depend on Beam Power

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