bene/care frascati 14-17 november 2006 cj densham cclrc rutherford appleton laboratory solid target...

BENE/CARE Frascati 14-17 November 2006 CJ Densham CCLRC Rutherford Appleton Laboratory

Solid target studies in UK for T2K and for a neutrino factory

JRJ Bennett, S Brooks, R. Brownsword, O Caretta, CJ Densham, R Edgecock, MD Fitton, VB Francis, S Gray,

A McFarland, M Rooney, G Skoro* and D WilkinsUnderlined are those who have given talks at BENE06

[email protected] Appleton Laboratory, Chilton, Didcot, Oxfordshire, UK

Except * Sheffield University, UK


Solid target studies in UK for T2K and for a neutrino factory

Partial summary of BENE06 presentations: T2K target station beam entry window

Matt RooneyDesign and Computational Fluid Dynamic analysis

of the T2K TargetMike Fitton

Shock wave experiments for T2K and Nufact target materials.

Chris DenshamFluidised beds: a new idea for a neutrino factory

targetOtto Caretta


T2K Secondary Beam Line

DV

TS

BD

Beam Dump(BD)•graphite core in helium vessel

Target station (TS) •Target & horns in helium vessel •Helium vessel and iron shields cooled by water Decay Volume (DV)

•94m long helium vessel cooled by water•6m thick concrete shield

‘280 m’ neutrino monitor

50 GeV PS ring

Primary beam lineFast extraction

Kamioka


T2K Target area

Inner iron shields

Inner concrete shields

Support structure= Helium vessel(being constructed by Mitsui Ship. Co.)

Baffle Target and 1st horns2nd horns

3rd horns

Beam window


The T2K Beam Window

Matt Rooney


Beam Window Assembly

Window Overview

- Double skinned partial hemispheres, 0.3 mm thick.- Helium cooling through annulus.- Ti-6Al-4V.- Inflatable pillow seal on either side.- Inserted and removed remotely from above.


Helium cooling of beam window

He in He out

Titanium - 0.3mm

Titanium -0.3mm

Helium3mm Gap

Upstream

Annulus

Downstream

Helium velocity ≈ 5 m/sHeat transfer coefficient ≈ 150 W/m2K


Stress Waves: effect of 8 bunches/beam spill

Stress wave development in 0.6 mm constant thickness hemispherical window over first 2 microbunches.


0.62 mm thick Ti-6Al-4V window - Constructive Interference between

bunches

-200

-150

-100

-50

0

50

100

150

200

0 1 2 3 4 5

Time from beginning of pulse (μs)

Stre

ss (M

Pa)

Von MisesHoopLongitudinal


0.3 mm thick Ti-6Al-4V window - Destructive interference between

bunches

-200

-150

-100

-50

0

50

100

150

200

0 1 2 3 4 5

Time from beginning of pulse (μs)

Stre

ss (M

Pa)

Von MisesHoopLongitudinal


Important lesson: thicker is not always stronger!

• With a pulsed proton beam, window and target geometry can greatly affect the magnitude of stress.

• Be careful to check dynamic stress when changing beam parameters or target and window geometry!


Design and Computational Fluid Dynamic analysis of the T2K

Target

Mike Fitton


RAL target design in the 1st Horn


Helium cooling flow path

Matt Rooney’s initial calculations suggest this window is ok for pressure and shock.

Inlet Manifold

Outlet Manifold

Flow turns 180° at downstream window


Animation of flow


Velocity StreamlinesCurrent design

Previous design iteration

Optimised for uniform flow


Velocity profile at downstream window

30 GeV, 0.4735Hz, 750 kW

Radiation damaged graphite

Optimisation for pressure drop and window cooling

Original Concept

Current RAL Design

•Pressure drop unacceptable

•No downstream window


30 GeV, 0.4735Hz, 750 kW

Radiation damaged graphite (20 [W/m.K])

Mass flow rate = 32 g/s

Steady state target temperature

Maximum temperature = 1009˚K = 736˚C


Radiation Damage of Graphite

For a radiation damaged target a thermal conductivity of 20 [W/m.K] is used (approx 4 times lower than new graphite at 1000°K)


T2K graphite target stress wavesMax Von Mises Stress: Ansys – 7MPa

LS-Dyna – 8Mpa

Max Longitudinal Stress: Ansys – 8.5MPaLS-Dyna – 10MPa

Ansys LS-Dyna


Shock wave experiments for T2K and Nufact target

material

Results from‘Shock Tests on Tantalum and

Tungsten’

- presented by Roger Bennett at Nufact06


Shock wave experiment at RALPulsed ohmic-heating of wires to replicate pulsed proton

beam induced shock waves in materials- using ISIS kicker magnet power supply

current pulse

Material test wire


LS-Dyna calculations

for shock-heating of

different graphite wire

radii

G.Skoro,

Sheffield University


Vertical Section through the Wire Test Apparatus

Current

Inner conductor of co-axial insulator feed-through.

Stainless steel split sphere

Copper “nut”

Current

Two graphite (copper) wedges

Spring clips

Fixed connection

Sliding connection

Test wire: Graphite (T2K) or Tungsten (nufact)


Some Results of 0.5 mm diameter wire tests and ‘equivalent’ nufact target parameters

36-

48

24

Beam PowerMW

4.2x106

+PLUS+

>9.0x106

>1.6x106

>3.4x106

0.2x106

No. of pulses to

failure

1900

2050

1900

2000

1800

Max. Temp

K

23-

12.5

12.5

130

140

5560

5840

2.5Not broken. Top graphite connector failed.

23

6.2517064003Stuck to top Cu connector

23

12.510049003Broke when increased to 7200A (2200K)

Tungsten

Tantalum is not a very good material – too weak at high temperatures.

12.56030004Tantalum

Target diacm

Rep RateHz

Pulse Temp

.K

Pulse Current

A

Lngth

cm

Material

“Equivalent Target”: This shows the equivalent beam power (MW) and target radius (cm) in a real target for the same stress in the test wire. Assumes a parabolic beam distribution and 4 micro-pulses per macro-pulse of 60 s.

Equivalent Target


Velocity Interferometry (VISAR) : to measure shock waves on material surface

Laser

Frequency ω Sample

Velocity u(t)

Fixed mirror

Beamsplitter

Etalon

Length hRefractive index n

Detector

Fixed mirror


Tungsten appears to be a candidate for a neutrino factory solid target and should last for several years.

In this time it will receive ~10-20 dpa. This is similar to the 12 dpa suffered by the ISIS tungsten target with no problems.

Tantalum is too weak at high temperatures to withstand the stress waves.


A new idea for NuFact targets and beam dumps

Otto Caretta


Work by Pugnat & Sievers

NuFact conceptual study for 1MW target

Tantalum packed bed (2mm particles) in flowing He

Already proposed by P. Sievers (CERN): packed bed targets

NuFact target


The new idea: a fluidised bed/jet

• A Fluidised jet of tungsten or tantalum particles in He could be used as a neutrino factory target– It could have high Z + high volume density– Can be effectively removed from the solenoid field hence

reducing the pion reabsorption– Can be replenished as particles wear out– Particles can be easily cooled (in an external fluidised bed)

A fluidised bed/jet of sand particlesof


Fluidised pipe flow vs injection

High concentration homogeneous particulate flow is difficult to maintain

over long distances

However the solid phase can be effectively collected in a conveyor and injected at/near the point of use in high concentrations (5:1 to

90:1 solid/gas)

Very similar to the jet produced by a grit blasting

device: it is all standard technology!


A fluidised bed/jet:

• Has the same advantages as the packed bed:– a near hydrostatic stress field develops in the particles so higher

energies can be absorbed before material damage– The flowing fluid provides high heat transfer so the bed can cope with

higher energy densities and total power (and perhaps more than one beam pulse)

• Plus some more:– Can have very high Z and density – Can be shaped as required– Can be easily renewed/replenished as the particles wear or get

damaged– Will absorb only the designed amount of energy and then flow out of

the scene to get cooled and replenished (if necessary)– It carries both the advantages of the solid phase (high density) and of

the liquid phase (metamorphic, pumpable, replenishable)


Particle jet as a NuFact target

solenoid

Particles jet

He flow

beam

Pionshower


BENE target work: the future

bene/care frascati 14-17 november 2006 cj densham cclrc rutherford appleton laboratory solid target...

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