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
• n 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

prototyping (NBI 2017) 2 20th September 2017

The Beam Dump Facility

20th September 2017

• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 3

• 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…”

• Material requirements for the target core
• High-Z materials
• Short interaction length
• Material selection à hybrid target
• 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

BDF target materials

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 4

To increase the reabsorption of pions and kaons (background for the experiment)

Target/dump

2nd part of the target: Tungsten à High-Z and good performance under irradiation 1st part of the target: TZM à Molybdenum alloy, higher strength and recrystallization temperature than Mo

12λ Nuclear inelastic scattering length

Target materials – Cooling

• Average beam power on target = 320 kW
• Water cooling needed: 5 mm gap between the blocks
• 200 m3/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

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 5

BDF target operation

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 6

Baseline characteristics Proton momentum [GeV/c] 400 Beam intensity [p+/cycle] 4.0·1013 Cycle length [s] 7.2 Spill duration [s] (slow extraction) 1.0 Average beam power on target [kW] 320 Average beam power on target during spill [MJ] 2.3

• High beam power deposited
• Requires dilution of the beam by

the upstream magnets

4*1013 ppp

7.2 s 1 s

BDF target operation

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 7

• Beam dilution optimization:
• Shape modified from

spiral trajectory to circle

• Multiple turns

20 40 60 80 100 120 140 160 180 0.2 0.4 0.6 0.8 1

Temperature (°C) Time (s)

Maximum temperature after 1 pulse, TZM core

1 turn 2 turns 4 turns

• Final configuration:
• Circular dilution
• 4 turns in 1 second

Thermal calculations

• Temperature limitations in the Ta cladding
• Ta properties at 180°C reduced

significantly with respect to RT

• High temperatures reached lead to a high

level of stresses in the core, cladding and interfaces

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 8

Energy deposition longitudinal distribution (FLUKA) Max temperature TZM core 190°C Max temperature Ta cladding 180°C Max temperature W core 150°C

40 80 120 160 200 5 10 15 20

Temperature (°C) Time (s)

TZM core Ta cladding W core

Thermal fatigue

ΔTTantalum ~ 140°C

Structural calculations

• The stresses reached in the TZM and tungsten cores are acceptable

with respect to the material limits for the temperatures reached

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 9

200 400 600 800 1000 1200 100 200 300 400

Strength [MPa] Temp [C]

Yield TZM (IAEA) Tensile TZM (IAEA) Tensile TZM stress relieved (Plansee)

TZM max Von Mises equivalent stress

TZM maximum Von Mises equivalent stress = 140 MPa @ 180°C

Maximum principal stress in Tungsten at 150°C HIPed + sintered tungsten tensile strength 20°C-500°C 80 MPa >400 MPa

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
• Foreseen material characterization campaign and

material R&D in order to evaluate the properties of the refractory metals at high temperatures

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 10

Maximum Von Mises equivalent stress at 180°C = 110 MPa Yield strength at 200°C ~ 70 MPa!

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

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 11

Maximum VM equivalent stress Ta2.5W (@180°C) = 110 MPa Yield strength Ta2.5W @200°C ~ 200 MPa

• 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

BDF target prototype

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 12

• Objective
• Reproduce the level of

temperatures and stresses of the final target

• Crosscheck the calculations

performed

• PIE foreseen after irradiation

BDF target prototype

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 13

• 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
• peration (10 hours)
• Removed from beam

for other experiments

BDF target prototype

• 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 = 3·1012 protons/pulse
• Total average power on target ~ 20 kW

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 14

Reduced scale prototype

Diameter reduced to 80 mm Same target length

Prototype thermal calculations

• Maximum temperature comparison: prototype vs. final target

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 15

100 200 300 5 10 15 20 25

Temperature (°C) Time (s)

Maximum temperature TZM core

Prototype target TZM core Final target TZM core 50 100 150 200 250 5 10 15 20 25

Temperature (°C) Time (s)

Maximum temperature Ta cladding

Prototype target Ta cladding Final target Ta cladding

Final BDF target BDF target prototype

Higher temperature reached in prototype Higher temperature reached in prototype Faster core cooling in prototype

20 40 60 80 100 120 5 10 15

Stress (MPa) Time (s)

Maximum eq. VM Stress – Ta cladding

Final target Ta cladding Prototype Ta cladding

Prototype structural calculations

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 16

• Reasonable approximation
• f the level of stresses in

the core and cladding

50 100 150 5 10 15

Stress (MPa) Time (s)

Maximum eq. VM Stress – TZM core

Final target TZM core Prototype TZM core

15% difference 20% difference

• Limit for higher temperatures

àsurface temperature àboiling point of water

Higher stresses in the final target

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

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 17

• P. Avigni (CERN EN/CV)

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

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 18

• P. Avigni (CERN EN/CV)

Strain gauge

Water flow 16 bar 1 kg/s

instrumentation

• Beam instrumented with a shielded BTV camera

Prototype Instrumentation

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 19

• 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
• Test the instrumentation under high

pressure and high speed water

Radiation issues – PIE

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• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 20

• High level of radiation challenging for the test
• O(Sv/h) after 2 months cooling
• Remote handling of the target
• Instrumentation connectors + Water connectors
• PIE foreseen after the operation
• Characterize beam-induced property changes in the

structure and the bonding contact Ta-alloy/core + signs of material weakening

• ~6 months after operation: (remote) extraction of several

target blocks for PIE

Conclusions

• A hybrid target of TZM and tungsten cladded with

tantalum or a tantalum alloy is considered for the Beam Dump Facility

• FEM calculations have been performed, showing that

tantalum as cladding material would not withstand the stresses induced in the target, justifying the R&D of alternative cladding materials as Ta2.5W.

• A prototype of the BDF target with reduced dimensions

will be tested next year, in order to validate the thermomechanical calculations performed and to carry out a PIE in the radiated target.

20th September 2017

• E. Lopez Sola, BDF target design and

prototyping (NBI 2017) 21

• E. Lopez Sola, BDF target design and

prototyping (NBI 2017)

Thank you for your attention!

Acknowledgements: M. Calviani, B. Riffaud,

• L. Zuccalli, P. Avigni, J. Busom, J. Canhoto