1. Target/Horn Station for ESS ν SB Nikolaos Vassilopoulos IPHC/CNRS

2. ESS ν SB layout (adopted from EUROnu Super Beam, inspired by J-PARC (T2K)) Switching yard to four proton beams or accumulator rings Iron (2.2 m) and concrete (3.7 m) shielding Decay tunnel He vessel (25 m) PSU Beam dump Concrete surrounding shielding) (8 m) Concrete surrounding shielding (8 m) 4-targets/horns Vessel (He) EUROnu arXiv:1212.0732 2NV@ ESS ν SB, CERN

3. ESS ν SB target station EUROnu arXiv:1212.0732 3NV@ ESS ν SB, CERN

4. He vessels 4NV@ ESS ν SB, CERN

5. Why MW proton Beam power and which target ?  Need multi-MW power in order to explore new physics in neutrino oscillations  Past or current experiments function with less than 0.5 MW proton power on targets  Main problem target lifetime and irradiation of beam materiel Chris Densham, RAL EUROnu (past) and currently HiRadMat at CERN look for solutions 5

6. Packed-bed target for ESS ν SB He Temperature Ti max Temperature near the outlets  Packed Ti spheres (3-4 mm diameter)  Large surface area for heat transfer  Coolant able to access areas with highest energy deposition  Minimal stresses  Potential heat removal rates at the hundreds of kW level  Pressurised cooling gas required at high power levels EUROnu arXiv:1212.0732 Davenne Tristan/RAL 6NV@ ESS ν SB, CERN

7. Horn evolution Evolution of the horn shape after many studies:  Triangle shape (van der Meer) with target inside the horn: in general best configuration for low energy beams  Triangle with integrated target to the upstream inner conductor part: very good physics results but high energy deposition and stresses on the conductors  Forward-closed with integrated target: best physics results, best rejection of wrong sign mesons but high energy deposition and stresses  Forward-closed with target inside the horn: best compromise between physics and reliability  4-horn/target system to accommodate the MW power scale Evolution of the horn shape after many studies:  Triangle shape (van der Meer) with target inside the horn: in general best configuration for low energy beams  Triangle with integrated target to the upstream inner conductor part: very good physics results but high energy deposition and stresses on the conductors  Forward-closed with integrated target: best physics results, best rejection of wrong sign mesons but high energy deposition and stresses  Forward-closed with target inside the horn: best compromise between physics and reliability  4-horn/target system to accommodate the MW power scale details in WP2 notes @ http://www.euronu.org/ 7NV@ ESS ν SB, CERN

8. ESS ν SB horn studies Horn structure  Al 6061 T6 alloy good trade off between mechanical strength, resistance to corrosion, electrical conductivity and cost  Four-horns assembly Horn stress and deformation  Static mechanical model: thermal dilatation  Magnetic pressure pulse: dynamic displacement  60 planar or elliptical water jets for cooling, flow rate between 60-120l/min, heat cooling coefficient 1-7 kW/(m 2 K)  Horn lifetime at least 1 year from fatigue analysis (30 – 60 MPa max stress - depending on cooling) Horn structure  Al 6061 T6 alloy good trade off between mechanical strength, resistance to corrosion, electrical conductivity and cost  Four-horns assembly Horn stress and deformation  Static mechanical model: thermal dilatation  Magnetic pressure pulse: dynamic displacement  60 planar or elliptical water jets for cooling, flow rate between 60-120l/min, heat cooling coefficient 1-7 kW/(m 2 K)  Horn lifetime at least 1 year from fatigue analysis (30 – 60 MPa max stress - depending on cooling) EUROnu arXiv:1212.0732 NV@ ESS ν SB, CERN 8

9. Four-horn support displacement (m) foreseen design Piotr Cupial et al., Krakow EUROnu arXiv:1212.0732 9 NV@ ESS ν SB, CERN

10. Energy Deposition from secondary particles, 3 horns, ESS ν SB -1.6 MW/EUROnu -1.3 MW P tg = 212/104 kW P h = 52/32 kW 13.6/9.4 kW 3.5/2.4 kW 2.4/1.7 kW 2.1/1.2 kW 21/12.4 kW, t=10 mm 2.8/1.6 kW target Ti=65%d Ti, R Ti =1.5 cm 6.3/3.4 kW, t=10 mm Horn max radial profile of power density kW/cm 3  large increase of power (~x2) deposited on target @ ESS FLUKA 2014, flair 10NV@ ESS ν SB, CERN

11. Horn cooling, EUROnu cooling system  Planar and/or elliptical water jets  30 jets/horn, 5 systems of 6-jets longitudinally distributed every 60 0  Flow rate between 60-120l/min, heat cooling coefficient 1-7 kW/(m 2 K)  Longitudinal repartition of the jets follows the energy density deposition  {h corner, h horn, h inner, h convex }= {3.8, 1, 6.5, 0.1} kW/(m 2 K) for T Al-max = 60 0 C cooling system  Planar and/or elliptical water jets  30 jets/horn, 5 systems of 6-jets longitudinally distributed every 60 0  Flow rate between 60-120l/min, heat cooling coefficient 1-7 kW/(m 2 K)  Longitudinal repartition of the jets follows the energy density deposition  {h corner, h horn, h inner, h convex }= {3.8, 1, 6.5, 0.1} kW/(m 2 K) for T Al-max = 60 0 C power distribution on Al conductor secondary particles (66%) + joule (34 %) 11NV@ ESS ν SB, CERN

12. displacements and stress plots just before and on the peak maximum stress on the corner, upstream inner and convex regions uniform temperature minimizes stress, max = 30 MPa displacements and stress plots just before and on the peak maximum stress on the corner, upstream inner and convex regions uniform temperature minimizes stress, max = 30 MPa Horn’s stresses due to thermal dilatation and magnetic pressure for 350 kA @ 12.5 Hz, EUROnu S max = 30 MPa modal analysis, eigenfrequencies f = {63.3, 63.7, 88.3, 138.1, 138.2, 144.2} Hz modal analysis, eigenfrequencies f = {63.3, 63.7, 88.3, 138.1, 138.2, 144.2} Hz T unif. = 60 0 C u max = 2.4 mm S max = 60 MPa T max = 60 0 C u max = 1.12 mm inner outer t= 79.6 ms t= 80 ms deformation stress or 12NV@ ESS ν SB, CERN

13. horn lifetime lower than 60 MPa expected highly conservative 1.25 10 8 pulses = 200 days = 1 year 13NV@ ESS ν SB, CERN

14. Perfect focusing vs nf vs focus ESS ν SB, 1 horn, no reflector CNGS, 1 horn + 1 reflector pf with 22 mrad acceptance (x28) with 1500 mrad acceptance (x14.7) GeV x10 14NV@ ESS ν SB, CERN

15. particles per p.o.t. ESS ν SB target: particle production π + production FLUKA 2014 detected 15NV@ ESS ν SB, CERN

16. 0 ms 20 40 60 80 1.5 μ s 12.5 Hz 50 Hz PSU EUROnu : Direct discharged and capacitive energy recovery through recovery circuit τ 0 = 100 μ s I 0 =350 kA, 1.5 μ s, T = 80 ms H - in at 50 Hz, 1.5 μ s long 1 horn focus : 12.5 Hz, 350 kA for 1.5 μ s PSU works at 50 Hz for 4 horns V0V0 VcVc I Cost Component limitation 1 st horn 2 nd horn 3 rd horn 4 th horn Modular approach p + linac 2013, JINST, 8, T07006 arXiv: 1304.7111 16

17. PSU EUROnu PSU: 8 times 4x44 kA modules 1-charger/capacitor/coil, 4-switches per 4x44 kA module 8 strip lines merged into 4 transmission lines in-out/horn 97 % Energy recuperation a 4x44 kA module x 8 17

18. linac Beam switching yard Accum. rings Dipoles, Quads triplets 4 horn/target He vessel 56 Hz ν 14 Hz H - 2.8 ms 0 ms 17.85 35.71 53.57 ms 71.4 2.8 ms 1.5 μ s H -, each horn 14 Hz 56 Hz ESS ν SB: 4-rings, ν at 56 Hz 18

19. linac Beam switching yard Accum. rings Dipoles, Quads 4 horn/target He vessel ν ESS ν SB: 4-rings, ν at 112 Hz + 35.71 ms neutron gap 0 ms 8.925 35.71 ms m s 71.4 2.8 ms 1.5 μ s H -, each horn at 14 Hz 112 Hz Neutron users for 32.9 ms 17.8526.775 28 Hz H -, p + 2.8 ms baseline 19

20. linac Beam switching yard Accum. ring Dipoles, Quads 4 horn/target He vessel ESS ν SB:1 ring, ν 1428 Hz (4 times every 0.7 ms) + 68.6 ms gap 0.7 ms 1.4 35.71 ms 71.4 2.8 ms 1.5 μ s 1428 Hz 2.12.8 14 Hz H - 2.8 ms 0 H -, each horn at 14 Hz ν 20

21. for Experimental Hall (Target/Horns, DT, Beam Dump), Safety Gallery, Maintenance Room, Waste Area 21NV@ ESS ν SB, CERN

22. ESS ν SB power distribution iron, concrete, molasse, He P tot = 4.2 MW beam dump graphite = 950 kW iron = 195 kW surr. concrete= 4 kW decay tunnel iron vessel = 424 kW upstream iron = 670 kW surr. concrete = 467 kW horns/target gallery iron = 613 kW horn = 50 kW target = 168 kW kW/cm 3 FLUKA 2013, flair 22 NV@ ESS ν SB, CERN

23. ESS ν SB neutron flux iron, concrete, molasse, He neutron/cm 2 /p + EUROnu shielding achieves 10 μ Sv/h prompt irradiation on the floor above target and horn 23NV@ ESS ν SB, CERN

24. Comments, future work Packed-bed target: A CFD model of a packed bed target concept for 1MW beam power indicates the feasibility of such a target (EUROnu) Vibration levels and relative motion and wear between spheres is as yet an unknown: an in-beam test needed (HiRadMat at CERN ?) Induction heating offers potential for an offline test of the heat transfer and pressure drop characteristics of a packed bed design Horn: “Too hard to die” in neutrino experiments. Preliminary fatigue studies (EUROnu) show horn’s lifetime > 1 year (10 8 ) cycles. Further studies needed Achieving proper cooling is crucial for the horn’s lifetime: tests needed for the existing design PSU: Build and test a 4x44 kA module Horn/Target station, ESS ν SB layout: Shielding design: to confine the radiation, to minimize prompt and residual irradiation under ALARA principles and local safety rules as in EUROnu. Cooling Lessons to be learnt from CNGS, T2K designs C. Densham et al., RAL 24NV@ ESS ν SB, CERN

25. WP breakdown structure ESS ν SB-secondary beam  Target  Horn  Four targets/horns assembly  Horn’s power supply  Decay tunnel  Beam dump Design (all) Beam window (target station) Physics (target-horn-decay tunnel) Cooling (all) Shielding, irradiations, etc… (all) Cost (all) Safety (all) Target station topics subtopics 25NV@ ESS ν SB, CERN Thanks

26. horn/target gallery 5 cm longitudinal holes transversal 3 cm see-through holes – to see the effect 26NV@ ESS ν SB, CERN

27. Yoshikazu Yamada on J-PARC Safety 27NV@ ESS ν SB, CERN

28. Be @ 4 MW  Thermal stress depends on Δ T Can not be overcome with more aggressive surface cooling  Break the 4 MW to 4 x 1 MW targets NV@ ESS ν SB, CERN28

29. Material @ multi-MW proton beam Hg, too many neutrons Gr thermo-conductivity degradation due to radiation Be operates at the stress limit Packed-bed with Ti spheres promising due to transversal cooling (EUROnu Super Beam solution) Fluidised power target potential solution for high heat removal Cooling Water-peripheral avoided due to water hammer cavitation He: beam transparent, less activation He-transversal, larger cooling area, preferable to Packed-bed target 29NV@ ESS ν SB, CERN

30. Beam window 0.25 mm thick beryllium window Circumferentially water cooled (assumes 2000 W/m 2 K) Max temp ~ 180 °C Max stress ~ 50 MPa (109 o C and 39 MPa using He cooling) Matt Rooney/RAL For SPL Super Beam MW 30NV@ ESS ν SB, CERN

31. Packed-bed target for ESS ν SB He Temperature Ti max Temperature near the outlets  Packed Ti spheres (3-4 mm diameter)  Large surface area for heat transfer  Coolant able to access areas with highest energy deposition  Minimal stresses  Potential heat removal rates at the hundreds of kW level  Pressurised cooling gas required at high power levels EUROnu arXiv:1212.0732 Davenne Tristan/RAL 31NV@ ESS ν SB, CERN

32. Stresses for the Packed bed target EUROnu example, 24mm diameter cannister packed with 3mm Ti6Al4V spheres  Quasi thermal and Inertial dynamic stress components ideally spill time > oscillation period Davenne Tristan/RAL 32 NV@ ESS ν SB, CERN

33. focusing-defocusing effect of the optics π +, π - at the entrance of decay tunnel CNGS: Stronger focusing effect due to higher beam energy, lower θ ’s and acceptance @ production ESS ν SB: good focusing effect, large θ ’s and wider acceptance range @ production steradian 33NV@ ESS ν SB, CERN

34. Alternative solution: pencil “closed” Be Solid target  Pencil like Geometry merits further investigation Steady-state thermal stress within acceptable range Shorter conduction path to coolant Pressurized helium cooling appears feasible Off centre beam effects could be problematic? Needs further thermo-mechanical studies 34NV@ ESS ν SB, CERN

35. Horn cooling, EUROnu cooling system  Planar and/or elliptical water jets  30 jets/horn, 5 systems of 6-jets longitudinally distributed every 60 0  Flow rate between 60-120l/min, heat cooling coefficient 1-7 kW/(m 2 K)  Longitudinal repartition of the jets follows the energy density deposition  {h corner, h horn, h inner, h convex }= {3.8, 1, 6.5, 0.1} kW/(m 2 K) for T Al-max = 60 0 C cooling system  Planar and/or elliptical water jets  30 jets/horn, 5 systems of 6-jets longitudinally distributed every 60 0  Flow rate between 60-120l/min, heat cooling coefficient 1-7 kW/(m 2 K)  Longitudinal repartition of the jets follows the energy density deposition  {h corner, h horn, h inner, h convex }= {3.8, 1, 6.5, 0.1} kW/(m 2 K) for T Al-max = 60 0 C power distribution on Al conductor secondary particles (66%) + joule (34 %) 35NV@ ESS ν SB, CERN

36. horn lifetime lower than 60 MPa expected highly conservative 1.25 10 8 pulses = 200 days = 1 year 36NV@ ESS ν SB, CERN

37. 4x44 kA module Capacitor charger 37NV@ ESS ν SB, CERN

38. figure of merit, parameter ε “variance” ε = 1-cos α α = τ H- /2. π / τ 0 in radians τ 0 = 100 μ s π How flat is the current pulse at peak ? How it correlates with H - beam width τ H- ? τ H- 1.5 μ s τ H- 1.5 μ s ε is correlated to energy storage power consumption the smaller ε the costlier or not feasible (the larger the integral I x Time) capacitor value vs width of H - beam 38NV@ ESS ν SB, CERN

39. 4-rings, ν at 56 Hz, ε analyses EUROnu, ε = 0.00026 39NV@ ESS ν SB, CERN

40. linac Beam switching yard Accum. rings Dipoles, Quads 4 horn/target He vessel 2.a) 4-rings, ν at 14 Hz-simultaneously 0 ms 35.71 71.4 2.8 ms 1.5 μ s Neutron users (or not) for 32.9 ms 28 Hz H -, p + 2.8 ms H -, 1-horn at 14 Hz EUROnu modifications 14 Hz ν 40

41. linac Beam switching yard Accum. rings Dipoles, Quads 4 horn/target He vessel 2.b) 4-rings, ν at 14 Hz-simultaneously, 4-horns chained in series, transformer 0 ms 35.71 71.4 2.8 ms 1.5 μ s Neutron users (or not) for 32.9 ms 28 Hz H -, p + 2.8 ms H -, 1-horn at 14 Hz EUROnu modifications 14 Hz ν 41NV@ ESS ν SB, CERN

42. EUROnu level linac Beam switching yard Dipoles+Quads 4 horn/target He vessel 4.a) no ring, ν during 2.8 ms (4 horns x 0.7 ms) + 68.6 ms gap, transformer 71.54 ms 2.8 ms 14 Hz H - 2.8 ms 0 ms 1 st 2 nd 3 rd 4 th horn H -, 1-horn at14 Hz 14 Hz ν 2.8 ms 42

43. Radiation Studies I prompt dose rates vs. concrete depth on the floor above shielding iron collimator for power supply area 10 μ Sv EUROnu studies