BDF target design and prototyping 10th International Workshop on - PowerPoint PPT Presentation

BDF target design and prototyping 10th International Workshop on neutrino beams & instrumentation (NBI 2017) 18th–22nd September 2017 E. Lopez Sola on behalf of the BDF Project CERN, Engineering Department, STI/TCD

Outline • Beam Dump Facility • Target materials and operation • Thermo-structural calculations • Material R&D • BDF Target prototype E. Lopez Sola, BDF target design and 2 20th September 2017 prototyping (NBI 2017)

The Beam Dump Facility • Beam Dump Facility target • Located in the North Area at CERN • Multipurpose fixed target, currently on design phase • Dedicated to SHiP experiment in a first stage “Explore the domain of hidden particles, such as Heavy Neutral Leptons, dark photons, supersymmetric particles…” E. Lopez Sola, BDF target design and 3 20th September 2017 prototyping (NBI 2017)

BDF target materials Target/dump • Material requirements for the target core • High-Z materials To increase the reabsorption of pions and • Short interaction length kaons (background for the experiment) • Material selection à hybrid target 1 st part of the target: TZM 2 nd part of the target: à Molybdenum alloy, higher Tungsten à High-Z and good strength and recrystallization performance under irradiation temperature than Mo 12λ Nuclear inelastic scattering length • Target core dimensions: • 250 mm diameter cylinders à contain cascade generated • Variable cylinder length à optimized segmentation of the target to minimize the level of stresses. Total target length ~ 1.5 m E. Lopez Sola, BDF target design and 4 20th September 2017 prototyping (NBI 2017)

Target materials – Cooling • Average beam power on target = 320 kW • Water cooling needed: 5 mm gap between the blocks • 200 m 3 /h of pressurized water at 20 bar • 2 m/s water velocity • All the blocks will be cladded with a 1.5 mm Tantalum layer , to protect the core materials from erosion-corrosion effects • Ta cladded to the TZM/W cylinders by Hot Isostatic Pressing (HIP) à mechanical and chemical bonding E. Lopez Sola, BDF target design and 5 20th September 2017 prototyping (NBI 2017)

BDF target operation Baseline characteristics Proton momentum [GeV/c] 400 1 s Beam intensity [p+/cycle] 4.0·10 13 4*10 13 ppp Cycle length [s] 7.2 Spill duration [s] (slow extraction) 1.0 Average beam power on target [kW] 320 7.2 s Average beam power on target 2.3 during spill [MJ] • High beam power deposited • Requires dilution of the beam by the upstream magnets E. Lopez Sola, BDF target design and 6 20th September 2017 prototyping (NBI 2017)

BDF target operation • Beam dilution optimization: • Shape modified from spiral trajectory to circle • Multiple turns Maximum temperature after 1 pulse, TZM core 1 turn 2 turns 4 turns 180 160 Temperature (°C) 140 120 100 80 60 40 20 0 0 0.2 0.4 0.6 0.8 1 Time (s) • Final configuration: • Circular dilution • 4 turns in 1 second E. Lopez Sola, BDF target design and 7 20th September 2017 prototyping (NBI 2017)

Thermal calculations Max Energy deposition longitudinal Max Max temperature distribution (FLUKA) temperature temperature TZM core 190 ° C W core 150 ° C Ta cladding 180 ° C • Temperature limitations in the Ta cladding TZM core Ta cladding W core • Ta properties at 180°C reduced 200 significantly with respect to RT Temperature (°C) 160 120 • High temperatures reached lead to a high 80 level of stresses in the core, cladding and 40 ΔT Tantalum ~ 140°C interfaces 0 Thermal fatigue 0 5 10 15 20 Time (s) E. Lopez Sola, BDF target design and 8 20th September 2017 prototyping (NBI 2017)

Structural calculations • The stresses reached in the TZM and tungsten cores are acceptable with respect to the material limits for the temperatures reached Maximum principal HIPed + sintered stress in Tungsten tungsten tensile strength at 150°C 20°C-500°C 80 MPa >400 MPa 1200 1000 TZM maximum Strength [MPa] 800 Von Mises 600 equivalent stress Yield TZM (IAEA) TZM max Von Mises 400 Tensile TZM (IAEA) = 140 MPa @ equivalent stress 200 Tensile TZM stress 180°C relieved (Plansee) 0 0 100 200 300 400 Temp [C] E. Lopez Sola, BDF target design and 9 20th September 2017 prototyping (NBI 2017)

Structural calculations • The level of stresses in the Ta cladding may be critical (bonding interface) • Low strength at high temperatures • Fatigue effects to be considered (few data at high temperatures) • Radiation effects to be taken into account Maximum Von Mises equivalent stress at 180°C = 110 MPa Yield strength at 200°C ~ 70 MPa! • Foreseen material characterization campaign and material R&D in order to evaluate the properties of the refractory metals at high temperatures E. Lopez Sola, BDF target design and 10 20th September 2017 prototyping (NBI 2017)

Material R&D • Solution: use of a tantalum-tungsten alloy, Ta2.5W • 2.5% content of W • Similar thermal properties to Ta • Higher strength, specially at high temperatures • Corrosion-erosion resistance • Bonding quality to tungsten and TZM expected to be the same • Ongoing R&D to study the cladding of Ta2.5W to TZM and W by HIPing Maximum VM equivalent stress Ta2.5W (@180°C) = 110 MPa Yield strength Ta2.5W @200°C ~ 200 MPa E. Lopez Sola, BDF target design and 11 20th September 2017 prototyping (NBI 2017)

BDF target prototype • Design and manufacture of a target prototype • Tested in the North Area at CERN during 2018 • High intensity beam (up to 1e13 protons) • Slow extraction: 1s pulse, 7.2 period • Beam non-diluted • Dedicated beam during 2 or 3 periods of 10 hours • Objective • Reproduce the level of temperatures and stresses of the final target • Crosscheck the calculations performed • PIE foreseen after irradiation E. Lopez Sola, BDF target design and 12 20th September 2017 prototyping (NBI 2017)

BDF target prototype • Timeline: • February 2018: Preparation of the area • March 2018: Installation of the target • Summer 2018: Testing • Prototype target on alignment table • Placed on beam during operation (10 hours) • Removed from beam for other experiments E. Lopez Sola, BDF target design and 13 20th September 2017 prototyping (NBI 2017)

BDF target prototype Reduced scale prototype Diameter reduced to 80 mm Same target length • Target core: TZM and W blocks cladded with Ta or Ta2.5W • Most critical blocks cladded with Ta2.5W • Several iterations to determine the beam intensity and cooling parameters needed to reproduce the state of temperatures and stresses • Beam intensity = 3·10 12 protons/pulse • Total average power on target ~ 20 kW E. Lopez Sola, BDF target design and 14 20th September 2017 prototyping (NBI 2017)

Prototype thermal calculations • Maximum temperature comparison: prototype vs. final target Maximum temperature Ta cladding Maximum temperature TZM core 300 250 Higher temperature Higher temperature Temperature (°C) Temperature (°C) reached in prototype reached in prototype 200 200 150 Faster core 100 100 cooling in 50 prototype 0 0 0 5 10 15 20 25 0 5 10 15 20 25 Time (s) Time (s) Prototype target TZM core Final target TZM core Prototype target Ta cladding Final target Ta cladding Final BDF target BDF target prototype E. Lopez Sola, BDF target design and 15 20th September 2017 prototyping (NBI 2017)

Prototype structural calculations Maximum eq. VM Stress – TZM core Maximum eq. VM Stress – Ta cladding Final target TZM core Prototype TZM core Final target Ta cladding Prototype Ta cladding 150 15% difference 20% difference 120 Stress (MPa) 100 100 80 Stress (MPa) 60 50 40 20 0 0 0 5 10 15 0 5 10 15 Time (s) Time (s) Higher stresses in the final target • Reasonable approximation of the level of stresses in the core and cladding • Limit for higher temperatures à surface temperature à boiling point of water E. Lopez Sola, BDF target design and 16 20th September 2017 prototyping (NBI 2017)

Prototype cooling system design • Circuit supply pressure: 22 bar • Initial design of the water cooling circuit • Water flowing on top/bottom of each block and through 5 mm channels between the blocks • Non-homogenous velocity • Cooling of the circular faces of the cylinders à beam impact P. Avigni (CERN EN/CV) E. Lopez Sola, BDF target design and 17 20th September 2017 prototyping (NBI 2017)

Prototype cooling system design • Several iterations to optimize the water flow • Homogeneous water velocity in the channels • High speed à high HTC value (16000 W/m2k) • Final choice: “guided” water flow • Blockers on top/bottom of each block • Water velocity in the channels = 4 m/s P. Avigni (CERN EN/CV) E. Lopez Sola, BDF target design and 20th September 2017 18 prototyping (NBI 2017)

Prototype Instrumentation • Beam instrumented with a shielded BTV camera instrumentation • Several target blocks instrumented with temperature and strain gauges • Instrumentation challenges • High levels of radiation • High water velocity in the block channels • Test-bench foreseen next month Strain gauge Water flow • Test the instrumentation under high 16 bar pressure and high speed water 1 kg/s E. Lopez Sola, BDF target design and 19 20th September 2017 prototyping (NBI 2017)