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

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: ESS ν SB, Lund

Super Beam Four-target/horns station EUROnu arXiv: ESS ν SB, Lund

He vessels ESS ν SB, Lund

Yoshikazu Yamada on J-PARC Safety ESS ν SB, Lund

MW proton Beam power  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 6

multi-MW 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 ESS ν SB, Lund

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 ESS ν SB, Lund

Packed-bed target 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: Davenne Tristan/RAL ESS ν SB, Lund

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 10

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 ESS ν SB, Lund

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 l/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 l/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:

Four-horn support (EUROnu) displacement (m) foreseen design Piotr Cupial et al., Krakow EUROnu arXiv:

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 ESS FLUKA 2014, flair ESS ν SB, Lund

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 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 ESS ν SB, Lund

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 ESS ν SB, Lund

particles per p.o.t. ESS ν SB target: particle production π + production FLUKA 2014 detected ESS ν SB, Lund

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 production ESS ν SB: good focusing effect, large θ ’s and wider acceptance production steradian ESS ν SB, Lund

ESS ν SB/EUROnu power distribution iron, concrete, molasse, He P tot = 4.2 / 3.4 MW beam dump graphite = 950/778 kW iron = 195/229 kW surr. concrete= 4/4 kW decay tunnel iron vessel = 424/390 kW upstream iron = 670/610 kW surr. concrete = 467/485 kW horns/target gallery iron = 613/437 kW horn = 50/ 32 kW target = 168/ 85 kW kW/cm 3 FLUKA 2013, flair ESS ν SB, Lund

0 ms 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:

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 21

linac Beam switching yard Accum. rings Dipoles, Quads triplets 4 horn/target He vessel 56 Hz ν 14 Hz H ms 0 ms ms ms 1.5 μ s H -, 1-horn 14 Hz 56 Hz ESS ν SB: 4-rings, ν at 56 Hz 22

4-rings, ν at 56 Hz, ε analyses EUROnu, ε = ESS ν SB, Lund

linac Beam switching yard Accum. rings Dipoles, Quads 4 horn/target He vessel ν ESS ν SB: 4-rings, ν at 112 Hz ms neutron gap 0 ms ms m s ms 1.5 μ s H -, 1-horn at 14 Hz 112 Hz Neutron users for 32.9 ms EUROnu modifications 28 Hz H -, p ms baseline 24

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) ms gap 0.7 ms ms ms 1.5 μ s 1428 Hz Hz H ms 0 H -, 1-horn at 14 Hz 14 Hz ν EUROnu modifications 25

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 ESS ν SB, Lund

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 ESS ν SB, Lund Thanks

horn/target gallery 5 cm longitudinal holes transversal 3 cm see-through holes – to see the effect ESS ν SB, Lund

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 ESS ν SB, Lund29

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 ESS ν SB, Lund

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 l/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 l/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 %) ESS ν SB, Lund

horn lifetime lower than 60 MPa expected highly conservative pulses = 200 days = 1 year ESS ν SB, Lund

for Experimental Hall (Target/Horns, DT, Beam Dump), Safety Gallery, Maintenance Room, Waste Area ESS ν SB, Lund

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 ESS ν SB, Lund

4x44 kA module Capacitor charger ESS ν SB, Lund

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 ESS ν SB, Lund

linac Beam switching yard Accum. rings Dipoles, Quads 4 horn/target He vessel 2.a) 4-rings, ν at 14 Hz-simultaneously 0 ms ms 1.5 μ s Neutron users (or not) for 32.9 ms 28 Hz H -, p ms H -, 1-horn at 14 Hz EUROnu modifications 14 Hz ν ESS ν SB, Lund37

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 ms 1.5 μ s Neutron users (or not) for 32.9 ms 28 Hz H -, p ms H -, 1-horn at 14 Hz EUROnu modifications 14 Hz ν 38

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) ms gap, transformer ms 2.8 ms 14 Hz H ms 0 ms 1 st 2 nd 3 rd 4 th horn H -, 1-horn at14 Hz 14 Hz ν 2.8 ms 39