Tungsten Powder Test at HiRadMat Scientific Motivation

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Tungsten Powder Test at HiRadMatScientific Motivation

P. Loveridge, T. Davenne, O. Caretta, C. Densham, J. O’Dell, N. Charitonidis23 April 2011

2 HiRadMat Scientific Board Meeting, 23 April 2011

Motivation

• Designing targets for new accelerator based facilities is becoming more and more challenging due to increasing accelerator beam power and the associated power deposition in the target.

• Targets must sometimes accommodate significant power deposition in continuous form or sometimes as an intense pulse followed by an interval of cooling.

• Maintaining the target temperature and stress levels within safe limits is the main design driver and results in increasingly elaborate designs as time averaged and pulse power deposition are increased

Solid peripherally cooled targets Segmented Targets

Flowing or rotating Targets

Increasing Power Deposition

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~940 mm

Titanium target body

Graphite(ToyoTanso IG-43)

Helium cooling

Graphite to titanium diffusion bond

Ti-6Al-4V tube and windows

(0.3 mm thick)

Solid targetsT2K target designed for750kW beam

Prefer small diameter to conduct heat to surface

Limit of approximately 1MW for peripherally cooled solid targets

Dynamic Stress in T2K Graphite Target After a Single Beam Spill at 400°C, Tspill = 4.2 micro-second

3.3e14 protons @ 30 GeV, beam sigma = 4.24mm, target diameter = 26 mm

-10

-5

0

5

10

0 1 2 3 4 5

Time (milli-sec)

Stre

ss (M

Pa)

VM-Str @ Gauge pt. Rad-Str @ Gauge pt. Long-Str @ Gauge pt.

Prefer large beam sigma to reduce dynamic stress due to pulsed beam

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Segmented targets

ISISEuronu superbeamPacked bed Concept for 4MW beam

Increased surface area. Coolant reaching maximum energy deposition region. Reduced static and dynamic stresses.

Increased beam power possible with thinner plates

0

50

100

150

200

250

300

350

1.00E-09 1.00E-08 1.00E-07 1.00E-06 1.00E-05

Peak

Von

-Mise

s St

ress

[MPa

]

Energy deposition time [seconds]

peak stress

expansion time

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Gap of 2mm

Flowing and rotating targets

Continuously refresh target material to accommodate multi-MW power deposition

SNS mercury target

5MW ESS target wheel concept

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0

200

400

600

800

1000

1200

1 10 100 1000 10000

Peak

tem

pera

ture

jum

p [K

]

Time averaged power deposited [kW]

Mu2e (8GeV, 25kW, 588kHz, 100ns, 1mm)

T2K (30GeV, 750kW, 0.47Hz, 5μs, 4.24mm)

Numi (120GeV, 400kW, 0.53Hz, 8μs, 1mm)

Nova (120GeV, 700kW, 0.75Hz, 8μs, 1.3mm )

LBNE (120GeV, 2.3MW, 0.75Hz, 10μs, 1.5mm+)

ISIS (800MeV, 160kW, 50Hz, 200ns, 16.5mm)

EURONu (4.5GeV, 4MW, 50Hz, 5μs, 4mm)

Neutrino Factory (8GeV, 4MW, 50Hz, 2ns, 1.2mm)

ESS (2.5GeV, 5MW, 14Hz, 2.86ms)

ADSR

Limitations of target technologies

Peripherally cooled monolith

Flowing or rotating targets

Segmented

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Thermal Shock in liquid targets

Merit, Flowing mercury jet 14GeV proton beam Kirk et al.

Pulsed proton irradiation of mercury target. Cavitation of mecury causing damage to annealed stainless steel containment LANSCE-WNR Riemer et al.

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Is there a ‘missing link’ target technology?

Some potential advantages of a flowing powder:Resistant to shock waves

Quasi-liquid: can be conveyed in a pipeOffline cooling

Few moving partsMature technology

Areas of concern can be tested off-line

Open jets

SOLIDS LIQUIDS

Monolithic Flowing powder Contained liquidsSegmented

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Open jet:

Contained discontinuous dense phase:

Contained continuous dense phase:

Potential Multi-MW Powder Target Applications

Powder target integrated with magnetic horn for superbeam

Powder target integrated with solenoid for Neutrino factory

10 HiRadMat Scientific Board Meeting, 23 April 2011

Tungsten Powder Test Programme

• Plant at RAL developed to do offline testing

– Dense phase and lean phase transport

– Erosion studies– Heat transfer and cooling of powder

1

2

3

4

1. Suction / Lift2. Load Hopper3. Pressurise Hopper4. Powder Ejection and Observation

Low Velocity

High Velocity

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Motivation for in-beam powder test

• Splash and cavitation in a liquid (mercury) is a result of propagation and reflection of pressure waves through a continuous medium.

• It has been asserted that powder will not be subject to splashing or violent events because of its discrete nature. Individual powder grains do not easily transmit pressure waves to neighbouring grains and as such pressure waves tend to be contained within the grains.

• A mechanism for a powder eruption has been identified as a result of a beam induced pressure rise in the carrier gas. The expansion of the carrier gas may be violent enough to aerodynamically lift some powder. While this is a potentially interesting threshold to find we expect that it will confirm that eruption velocities are small compare to the splashing velocities observed with mercury.

• In order to confirm these assertions the response of a powder target to the proton beam must be tested to definitively answer the following two questions

• Will a powder target splash/erupt?• Can you propagate a pressure wave through a powder target to its container?

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Mercury Thimble In-beam test