Overview of LBNF Target Conceptual Design Selection

1. Overview of LBNF Target Conceptual Design Selection Chris Densham (STFC Rutherford Appleton Laboratory) On behalf of combined UK and Fermilab LBNF Project team with all physics plots c/o John Back (Warwick University)

2. Our starting point: Helium Cooled T2K Target Target installation in magnetic horn using exchanger and manipulatorsystem Chris Densham

3. Target Concept Selection Process • 3 concepts developed in parallel over last year • 3 day ‘Target Concept Selection’ meeting at Fermilab July 23-25th found consensus • Conceptual Design Review held yesterday • …and now this… • …and next week I’ll give an invited talk at NuFACT2019 in Korea Chris Densham

4. Particle Production Target ‘Optimum’ Performance • λoverall = λphysics× λreliability , whereλreliability = fn(I,σ,L…) • For CP sensitivity – small beam σ is favoured • For target lifetime – bigger σ is better. • Lower power density – lower temperatures, lower stresses • Lower radiation damage rate • Lower amplitude ‘violin’ modes (and lower stresses) • For CP sensitivity – long target (c.2m, 4λ) is better • For max lifetime – short and simpletarget is better • For integrated optimum performance, need to take both instantaneous performance and reliability 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 parameters & power, changeout time etc

5. Helium cooled target concept selection 1: Single 2.2m long target with remote-docking downstream support 3: Single intermediate length (c.1.5 m or ‘As Long As Realistically Achieveable’ ) cantilever target 2: Two ~1m long cantilever targets, one inserted at either end of horn Chris Densham

6. Comparison of CP sensitivity for 3 options considered (all r = 8 mm, σ = r/3 • Option 1: downstream support offers best physics performance at c.2.2 m length • Option 2: Simple cantilever gives best performance for a given length (but may be limited to c.1.5 m) • Option3: Double 1m targets offer same performance as single 1.5 m cantilever Chris Densham

7. Target Concept Selection Criteria

8. Key Design and Manufacturing Issues

9. Key Operation Issues

10. Key Remote Maintenance Issues

11. Helium cooled target concept selection 1: Single 2.2m long target with remote-docking downstream support 3: Single intermediate length (c.1.5 m) target supported as a simple cantilever 2: Two ~1m long cantilever targets, one inserted at either end of horn Chris Densham

12. Integrated performance optimisation • To achieve same 3σ exposure for ΔCP sensitivity as 2.2 m long target: • 1.5 m cantilever or double target need to run extra 19 days/year • 1.6 m cantilever needs to run extra 13 days/year • Our judgment: c.1.5 m cantilever will deliver better integrated performance • Ultimate objective: ‘As Long As Realistically Achievable’ cantilever target Chris Densham

13. Neutrino flux for range of radii of 1.5 m long target Smaller radius target boosts higher energy neutrinos and antineutrinos (1st oscillation maximum) Larger radius target boosts lower energy neutrinos and antineutrinos (2nd oscillation maximum) Chris Densham

14. CP sensitivity for 1.5 m cantilever targetvs target & beam rmsradius • Comprehensive study of physics performance for range of beam and target radii • Need to compromise between physics and engineering performance • Some scope to improve CP sensitivity for given beam rms radius

15. LBNF helium cooled target conceptual design P+ Horn inner conductor ‘Bafflette’ mini-collimator enables beam-based alignment Graphite target rod ‘Hylen’ device BPM Chris Densham

16. LBNF conceptual design compared with current ‘state-of-the-art’ T2K@1.3 MW NB current experience up to 500 kW LBNF@1.2 MW Chris Densham

17. Dynamic stability as an indicator of ‘robustness’ (high frequency →low amplitude) First 3 natural frequency modes: Chris Densham

18. How can we optimise for maximum target length? • Factors point towards a tapered (cone shaped) outer container • potentially good for mechanics, thermal management, and physics! • Plenty of scope to optimise present design • Upstream part of CantileverBending moment → High, Volumetric heating → Low • Large tube diameter? • Large wall-thickness? • Compatible with vacuum buckling resistance ✓ Assess Mechanical Performance Geometry Update Assess Physics Impact Design Iterations • Downstream part of CantileverBending moment → Low , Volumetric heating → High • Small tube diameter? • Small wall-thickness? • Compatible with vacuum buckling resistance ✓ Assess Thermal Management Determine Heat Loads

19. Cantilever target integrated with Horn Chris Densham

20. Target replacement in Work Cell Shielding blocks Horn module supports 2x through-wall manipulators Work cell door 2x Lead glass windows Target Target exchanger Horn A Lift table Human side Hot side Outline Procedures

21. Target and baffletteintegrated into MARSLBNF Impact of target on other systems (e.g. Hadron Absorber) well understood by LBNF project team at Fermilab (Reitzner, Mokvov, Striganof) Chris Densham

22. Chris Densham