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)
Our starting point: Helium Cooled T2K Target Target installation in magnetic horn using exchanger and manipulator system Chris Densham 2
Target Concept Selection Process • 3 concepts developed in parallel over last year • 3 day ‘Target Concept Selection’ meeting at Fermilab July 23-25 th 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 3
Particle Production Target ‘Optimum’ Performance • λ overall = λ physics × λ reliability , where λ reliability = 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, 4 λ ) is better • For max lifetime – short and simple target 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 Chris Densham
Helium cooled target concept selection 3: Single intermediate length (c.1.5 m 1: Single 2.2m long target with or ‘As Long As Realistically remote-docking downstream support Achieveable ’ ) cantilever target 2: Two ~1m long cantilever targets, one inserted at either end of horn Chris Densham 5
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 6
Target Concept Selection Criteria 1 Physics performance Instantaneous physics performance Upgradeability to 2.4 MW Flexibility re optimisation (materials, beam size etc) Compatibility with beam alignment (hadron vs muon?) 2 Engineering performance Safety factor = f(stress, temperature) Lifetime, resilience to radiation damage Resilience to off-normal conditions Resilience to beam trips Potential for diagnostics 3 Impact on other systems Impact on horn/stripline design Ease of integration with horn Ease/reliability of alignment with horn axis Impact on services/plant Ease of remote handling/disposal Impact on TS design Impact on absorber design 4 Cost Cost & resource for design/prototyping Cost & resource for manufacture Cost of RH equipment Disposal cost 5 Schedule Time to design Time to prototype Time to manufacture Schedule impact on other systems 6 Risk Design complexity Ease of manufacture Remote handling complexity Departure from known technology Schedule risk ES&H / ALARA issues
Key Design and Manufacturing Issues Option 3: intermediate Option 1:1x2m long Option 2: 2x1m long cantilever Interfaces at both US and DS of Interfaces at both US and DS of Complexity of horn horn, plus self interface! horn. Needs Helium services Interface to horn US end only Needs Helium services routing to Interface routing to DS end. DS end. Departure from T2K in terms of Departure from Closest to two-interaction length Departure from T2K in terms of length / segmentation and Proven Technology T2K target length / segmentation Self docking interface. DS support design for radial DS support/manifold design w.r.t. Pushing for longest feasible stiffness + longitudinal Design Challenges pressure stress and thermal length (re: deflection, violin compliance, requires distortion. modes) prototyping. DS support manufacture is complex. US target most similar to T2K. Manufacture of long thin-walled Manufacturing Manufacture of long thin-walled DS low-mass manifold titanium tube to tight Challenges titanium tube to tight manufacture is complex. dimensional tolerances. dimensional tolerances. Relatively high cost of Relatively high cost of Relatively low cost of Cost manufacture and outstanding manufacture and outstanding manufacture and outstanding design tasks design tasks design tasks 8
Key Operation Issues Option 3: intermediate Option 1:1x2m long Option 2: 2x1m long cantilever Highest cost Intermediate cost Lowest cost Spare Production Build four (2 US + 2 DS) in Build two in parallel? Build two in parallel? parallel? Highest heat load, single target Thermal High heat load but divided cooling loop. Also need to cool Lowest total heat load Management between two cooling loops DS support. DS prop required to keep self- Most “robust” structure as Inherently pushing at the limits Mechanical loads weight deflection and natural measured by natural frequency on cantilever length frequency in check and self-weight deflection Complexity / High complexity due to High complexity due to cooled Low Complexity / number of number of failure additional downstream target downstream mount components system points Relies on DS support for target Perceived difficulties with beam Single object to align but largest Alignment Issues placement precision based alignment self-weight deflection 9
Key Remote Maintenance Issues Option 3: intermediate Option 1:1x2m long Option 2: 2x1m long cantilever Time estimate for planned target 3 weeks 2 weeks 1 week exchange High High Medium Risk / complexity (number of operations) (number of operations) (number of operations) Two sets of exchange tooling Two sets of exchange tooling Work Cell with mechanical/services with mechanical/services One exchanger tool Interfaces interface interface Ergonomics compromised when Manipulator Ergonomics compromised when Can optimise reach/view for the module rotated. Long-reach operations module rotated single required configuration manipulators. Two module rotations, including One module rotation, including All work achieved with single Crane operations re-configuration of supports etc re-configuration of supports etc module configuration 10
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 11
Integrated performance optimisation To achieve same 3 σ • exposure for Δ CP 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 12
Neutrino flux for range of radii of 1.5 m long target Smaller radius Larger radius target boosts target boosts higher energy lower energy neutrinos and neutrinos and antineutrinos antineutrinos (1 st oscillation (2 nd oscillation maximum ) maximum) Chris Densham 13
CP sensitivity for 1.5 m cantilever target vs target & beam rms radius 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 Chris Densham
LBNF helium cooled target conceptual design Horn ‘Bafflette’ inner mini- conductor collimator Graphite enables ‘Hylen’ target rod beam- device based BPM alignment Chris Densham 15
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 16
Dynamic stability as an indicator of ‘robustness’ (high frequency → low amplitude) First 3 natural frequency modes: Case LBNF NuMI T2K Deflection under 0.79 ≈0.9 ≈0.5 gravity (mm) Natural 1 22 14 28 Freq (Hz) (Horizon for mode: tal) 2 135 3 228 Chris Densham 17
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 Cantilever Bending moment → High, Volumetric heating → Low Large tube diameter? • Large wall-thickness? • Compatible with vacuum buckling resistance ✓ • Assess Mechanical Performance Geometry Assess Update Physics Design Impact Iterations Downstream part of Cantilever Bending moment → Low , Volumetric heating → High Assess Small tube diameter? • Thermal Determine Small wall-thickness? • Management Heat Loads Compatible with vacuum buckling resistance ✓ • 18
Cantilever target integrated with Horn Chris Densham 19
Target replacement in Work Cell Shielding blocks Horn module supports 2x through-wall Work cell manipulators door 2x Lead glass windows Target Target exchanger Horn A Lift table Human Hot side side Outline Procedures 20
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