Optimization of the target and magnetic horn for

Optimization of the target and magnetic horn for the CERN to Fréjus neutrino beam Nikolas Vassilopoulos, IPHC/CNRS, Strasbourg

Talk layout Ø Target Studies Ø Horn shape & Super. Beam Geometrical Optimization Ø Horn Thermo-mechanical Studies Ø Energy Deposition, Irradiation and Safety Studies SPL Super. Beam Studies @ NUFACT 11 2

Proton Beam and Target/Horn Station Ø Ø Ø Eb = 4. 5 Ge. V Beam Power = 4 MW -> 4 x 1 -1. 3 MW Repetition Rate = 50 Hz -> 12. 5 Hz Protons per pulse = 1. 1 x 1014 Beam pulse length = 0. 6 ms Ø 4 -horn/target system in order to accommodate the 4 MW Ø power @ 1 -1. 3 MW, repetition rate @ 12. 5 Hz for each target Ilias Efthymiopoulos/CERN SPL Super. Beam Studies @ NUFACT 11 3

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) feasible SPL Super. Beam Studies @ NUFACT 11 Matt Rooney 4

Important Issues for the engineering of the target Ø Heat Removal ü Ø Beam ≈ 60 – 120 k. W depending on Target Material/configuration Thermal/mechanical stresses long lived “quasi-static” stresses that generated by temperature variations within the target ü inertial dynamic stress waves that are generated by the pulsed nature of the beam ü Ø Cooling water ü helium ü peripheral vs transversal cooling ü Ø Ø Ø Neutron Production – heat load/damage of horn Safety Radiation resistance Reliability Pion yield SPL Super. Beam Studies @ NUFACT 11 Chris Densham et al. @ RAL 5

from Liquid Targets to Static Packed one SPL Super. Beam Studies @ NUFACT 11 EUROnu-W P 2 -note-1101 favourable baseline for WP 2 6

SPL Super. Beam Studies @ NUFACT 11 favourable methods 7

with peripheral cooling Ottone Caretta/RAL SPL Super. Beam Studies @ NUFACT 11 ruled out 8

SPL Super. Beam Studies @ NUFACT 11 9

Packed bed Target Ø Why packed bed target with transversal cooling is the baseline option ? ü Large surface area for heat transfer ü Coolant able to access areas with highest energy deposition ü Minimal stresses ü Potential heat removal rates at the hundreds of k. W level ü Pressurised cooling gas required at high power levels ü Bulk density lower than solid density ü From a thermal and engineering point of view seems a reasonable concept where stress levels in a traditional solid target design look concerningly high SPL Super. Beam Studies @ NUFACT 11 10

SPL Super. Beam Studies @ NUFACT 11 Tristan Davenne/RAL 11

Tristan Davenne/RAL SPL Super. Beam Studies @ NUFACT 11 12

Stresses for the Packed bed target EUROnu example, 24 mm diameter cannister packed with 3 mm Ti 6 Al 4 V spheres Ø Quasi thermal and Inertial dynamic components SPL Super. Beam Studies @ NUFACT 11 ideally spill time > oscillation period Tristan Davenne/RAL 13

Alternative solution: pencil “closed” Be Solid target Mike Fitton, Peter Loveridge/RAL Ø Pencil like Geometry merits further investigation ü Steady-state thermal stress within acceptable range ü Shorter conduction path to coolant ü Pressurized helium cooling appears feasible ü Off centre beam effects could be problematic? ü Needs furthermo-mechanical studies SPL Super. Beam Studies @ NUFACT 11 14

Horn Studies evolution of the horn shape after many studies: 2 notes @ P W n i s detail nu. org/ o r u e. w w http: //w Ø triangle shape (van der Meer) with target inside the horn : in general best configuration for low energy beam Ø triangle with target integrated to the inner conductor : very good physics results but high energy deposition and stresses on the conductors Ø forward-closed shape with target integrated to the inner conductor : best physics results, best rejection of wrong sign mesons but high energy deposition and stresses Ø forward-closed shape with no-integrated target: best compromise between physics and reliability Ø 4 -horn/target system to accommodate the MW power scale SPL Super. Beam Studies @ NUFACT 11 15

Horn Shape and Super. Beam geometrical Optimization Ø minimize λ, the δcp-averaged 99%CL sensitivity limit on sin 22θ 13 Ø broad scan, then fix & restrict parameters then re-iterate for best horn parameters & Super. Beam geometry A. Longhin/CEA SPL Super. Beam Studies @ NUFACT 11 16

Horn Stress Studies Ø horn structure ü Al 6061 T 6 alloy; good trade off between mechanical strength, resistance to corrosion and electrical conductivity and cost ü horn thickness has to be as small as possible for the best physics performance and to limit energy deposition from secondary particles but thick enough to sustain dynamic stress from the pulsed currents. Ø horn stress and deformation ü magnetic pressure and thermal dilatation ü COMSOL, ANSYS software Ø cooling ü water SPL Super. Beam Studies @ NUFACT 11 17

EUROnu scenario for 4 -horn system SPL Super. Beam Studies @ NUFACT 11 18

Stress Analysis for the SPL Super. Beam Horn I B. Lepers/IPHC, P. Cupial , L. Lacny/Cracow Univ. of Tech. Ø Thermo-mechanical stresses: ü secondary particles energy deposition and joule losses ü T=60 ms, τ0=100μs, Irms=10. 1 k. A, f=5 k. Hz (worst scenario, 1 horn failed) ü TAl =600 C, {hcorner , hinner, hhorn/out }= {6. 5, 3. 8, 0. 1} k. W/(m 2 K) ü Smax = 62 MPa SPL Super. Beam Studies @ NUFACT 11 B. Lepers/IPHC 19

Stress Analysis II Ø Combined analysis of Thermo-mechanical and magnetic pressure induced stresses: ü significant stress or the inner conductor especially, for the upstream corner and downstream plate inner part ü high stress at inner conductor welded junctions ü thermal dilatation contributes to longitudinal stress; displacement is low due to the magnetic pulse ü maximum displacement at downstream plate B. Lepers/IPHC Ø horn lifetime estimation: results have to be compared with fatigue strength data Ø more water-jet cooling might be applied SPL Super. Beam Studies @ NUFACT 11 displacement and stress time evolution , peak magnetic field each T=80 ms (4 -horns) 20

Cooling Studies B. Lepers, V. Zeter, IPHC power distribution on Al conductor ü planar and/or elliptical water jets ü flow rate between 60 -120 l/min ü h cooling coefficient 1 -7 k. W/(m 2 K) ü EUROnu-Note-10 -06 Ø design for 600 C uniform horn temperature: ü {hcorner , hinner , houter/horn }= {6. 5, 3. 8, 1} k. W/(m 2 K)/longitudinal repartition of the jets follows the energy density deposition ü 30 jets/horn, 5 systems of 6 -jets longitudinally distributed every 60 0 SPL Super. Beam Studies @ NUFACT 11 21

Power Supply Studies P. Poussot, J. Wurtz/IPHC horn focusing plateau energy recovery SPL Super. Beam Studies @ NUFACT 11 Energy recovery with an inductance L, switch and capacitor: Ø good energy recuperation 60% Ø best solution in terms of feasibility and cost 22

for Experimental Hall (Target/Horns, DT, Beam Dump), Safety Gallery, Maintenance Room, Waste Area SPL Super. Beam Studies @ NUFACT 11 23

Safety II beam dump spare area hot cell SPL Super. Beam Studies @ NUFACT 11 decay tunnel (25 m) shielding beam Design includes: Ø Proton Driver line Ø Experimental Hall ü MW Target Station ü Decay Tunnel ü Beam Dump Ø Maintenance Room Ø Service Gallery ü Power supply ü Cooling system ü Air-Ventilation system Ø Waste Area target/horn station horn power supply and electronics gallery 24

Energy deposition and Activation Studies FLUKA MC + FLAIR ACTIVITY density in Bq/cm 3 molasse concrete rock: molasse @ CERN concrete Fe shields, vessels graphite beam dump He vessels: T&H : L=8 m, t. Fe =10 cm , tconcrete=5. 7 cm DT : L =25 m, t. Fe =1. 6 cm , tconcrete=5. 6 cm BD : L =8 m, t. Fe =10 -40 cm , tconcrete=5. 7 cm POWER density in k. W/cm 3 molasse concrete Ptot =3. 4 MW Ø energy is confined from concrete thickness Ø minimum activation of molasse rock Ø minimum/none effective dose to humans in other galleries Ø detailed tables of the radionuclides Eric Baussan, Ø water contamination from tritium is well kept under safety levels N. Vassilopoulos/IPHC SPL Super. Beam Studies @ NUFACT 11 25

Energy Deposition in Beam Dump vessel Ø concrete: Ø t = 5. 6 m Ø L = 8. 4 m 530 k. W Ø He vessel + iron plates, water cooled Øt. Fe = 10 -40 cm ØLFe= 4 m Ø upstream shield (iron plates), water cooled Ø t. Fe = 40 cm Ø LFe = 1 m Ø Graphite beam dump: Ø L = 3. 2 m, W = 4 m, H = 4 m Ø P = 530 k. W Ø downstream iron shield (iron plates), water cooled: Ø LFe = 40 cm, WFe = 4 m, HFe = 4 m Ø PFe = 10. 3 k. W Ø outer iron shields (iron plates), water cooled Ø L Fe= 2 m, WFe = 4. 8 m, HFe = 4. 8 m Ø PFe = 1. 1 k. W SPL Super. Beam Studies @ NUFACT 11 26

Activation in molasse (full 4 horn simulation, medium stats: 10 6 molasse @ CERN protons, 20% error) concrete study set up: ü packed Ti target, 65%d. Ti ü 4 MW beam, 4 horns, 200 days of irradiation Activity distribution Ø minimum activation leads to minimum water contamination Ø concrete thickness determines the activation of the molasse results: Ø of all the radionuclide's created 22 Na and tritium could represent a hazard by contaminating the ground water. Limits in activity after 1 y=200 days of beam: CERN annual activity constraints in molasse (for achieving 0. 3 m. Sv for the public through water) Super. Beam, (preliminary) Na 4. 2 x 1011 Bq - (to be investigated) tritium 3. 1 x 1015 Bq 6 x 108 Bq 22 SPL Super. Beam Studies @ NUFACT 11 27

Target Activity at Storage Area study set up: Ø packed Ti target, 65%d. Ti Ø 1. 3 MW beam, 200 days of irradiation Ø no other activation at storage area SPL Super. Beam Studies @ NUFACT 11 Eric Baussan, N. Vassilopoulos/IPHC 28

Dose Rates for target/horn at Storage/Service Area, I radiation limits as in CNGS notes: Limits per 12 -months period (m. Sv) Public Workers France <1 < 20 Switzerland <1 < 20 < 0. 3 < 20, if. gt. 2 m. Sv/month CERN report to Swiss authorities rates (e. g. ): Øat 60 cm distance from the outer conductor (calculation of the rates using 20 cmx 20 cm mesh binning through out the layout -> choose a slice of xaxis with 20 cm thickness and 60 cm away ) z SPL Super. Beam Studies @ NUFACT 11 x 29

Dose Rates target/horn at Storage Area, II 1 month 1 year > 1 Sv/h > 50 m. Sv/h palette in m. Sv/h 50 years 100 years > 0. 01 m. Sv/h Ø high effective dose rates for the target/horn system makes them inaccessible -> remote handling mandatory SPL Super. Beam Studies @ NUFACT 11 Eric Baussan, N. Vassilopoulos/IPHC 30

Conclusions Ø Horn with separated target baseline as result of dynamic and static stress analyses Ø 4 -horn system to reduce the 4 MW power effects Ø Horn shape defined as forward-closed due to best physics results and reliability issues Ø Packed-bed Target is preferable in multi-Watt beam environment due to minimum stresses and high heat rate removal due to transverse cooling among others Ø Stress analysis support the feasibility of the target/horn design. Furthermore the power supply design looks feasible as well Ø Minimum activation in molasse rock for current secondary beam layout Ø High dose rates in Storage Gallery -> remote handling for repairs mandatory to be continued. . . SPL Super. Beam Studies @ NUFACT 11 Thanks 31

SPL Super. Beam Studies @ NUFACT 11 32

pen like target: cooling SPL Super. Beam Studies @ NUFACT 11 looks feasible 33

considerations: SPL Super. Beam Studies @ NUFACT 11 34

Horn shape and Super. Beam geometrical Optimization I , Longhin. A y b s studie 2 -10 -04 P W u n EURO parameterise the horn and the other beam elements as decay tunnel dimensions, etc. . . parameters allowed to vary independently minimize the δcp-averaged 99%CL sensitivity limit on SPL Super. Beam @ NUFACT 11 sin 22θStudies 13 ü ü 35

Horn Shape and Super. Beam geometrical Optimization II SPL Super. Beam Studies @ NUFACT 11 fix & restrict parameters then reiterate for best horn parameters & Super. Beam geometry 36

Physics Performance for different Targets I Ø Graphite Solid target, 2λI Ø Hg, 2λI Ø Integrated target, 2λI Ø excellent performance of packed bed Ti, d= 74%d. Ti CERN to Frejus/MEMPHYS neutrino beam SPL Super. Beam Studies @ NUFACT 11 d acke p f o g n uctio increasin d e r nsity perated , 100 k. A e d y cu 50 an be re rrent by d l u co rn cu o h e th 37

Physics Performance for different Targets II Ø Graphite Solid target, 2λI CERN to Frejus/MEMPHYS neutrino beam SPL Super. Beam Studies @ NUFACT 11 Ø Hg, 2λI Ø Integrated target, 2λI Ø excellent performance of packed bed Ti, d= 77%d. Ti d cke a p g n of reasin o i t c c edu ted in 100 k. A r y a , it ens ecuper t by 50 d y an be r curren d l cou horn the 38

Energy Deposition from secondary particles on Horn, 1. 3 MW, Ti packed bed target FLUKA MC+FLAIR target Ti=65%d. Ti , RTi=1. 5 cm 36 k. W, t=30 mm 8. 6 k. W, t=35 mm 9. 5 k. W radial profile of power density k. W/cm 3 SPL Super. Beam Studies @ NUFACT 11 W 2. 4 k 1. 7 k. W 1. 3 k W 2. 5 k. W Ptg = 105 k. W Ph = 62 k. W 39

Energy Deposition on horns # 2, 4, active horn is #1 1. 3 MW beam, 350 k. A, graphite target shown upstream plates 2 nd Etoth= 14. 4 k. W 1 st 3 rd 4 th Etoth= 0. 8 k. W 2 nd or 4 th Power in k. W for the horns next to the active one total 0. 8 (5. 5% of active horn) inner outer plates 0. 1 0. 6 (50% of outer next to 1 st) 0. 1 SPL Super. Beam Studies @ NUFACT 11 40

SPL Super. Beam Studies @ NUFACT 11 41

Energy deposition on Super. Beam Elements Power density distributions in k. W/cm 3 concrete P=530 k. W P=3. 4 MW DT Fe vessel 320 k. W water SPL Super. Beam Studies @ NUFACT 11 DT concrete Gr Beam Dump 720 k. W 530 k. W Gr beam dump water 42

<doses> in longitudinal plane along beam axis after 200 d of irradiation DT area Beam Dump 6 months Ho rn s 1 day DT area Beam Dump palette in m. Sv/h DT area 10 years Beam Dump Ho rn s 1 year DT area Beam Dump Ø high dose rates along Super. Beam layout->remote handling mandatory for any part of the 4 -horn system in target/horn station SPL Super. Beam Studies @ NUFACT 11 43