A powder jet target for a Neutrino Factory Ottone Caretta, Chris Densham (RAL), Tom Davies (Exeter...

A powder jet target for a Neutrino Factory

Ottone Caretta, Chris Densham (RAL), Tom Davies (Exeter University), Richard

Woods (Gericke Ltd)

Chris Densham UKNF 3rd Oct 2007

Open jets

Target technology problems:

Power dissipationRadiation damage

Shock waves/ thermal stress

MovingSegmentedMonolithicContained

liquids

Increasing power

SOLIDS LIQUIDS

Cooling Lubrication/ tribology Reliability

Shock waves, Cavitation Corrosion

Radiochemistry

Splashing, radiochemistry,

corrosion

Challenges:

Chris Densham UKNF 3rd Oct 2007

T2K at JPARC

Next Generation Long Baseline Neutrino Oscillation Experiment

Chris Densham UKNF 3rd Oct 2007

Solid T2K target supported within the 1st Horn

Helium cooling pipe

Chris Densham UKNF 3rd Oct 2007

Graphite to titanium diffusion bond

Graphite-to-graphite bond

Flow turns 180° at downstream

window

Inlet manifold

Outlet manifold

Upstream

Window

T2K Target Design:

Helium cooling path

Chris Densham UKNF 3rd Oct 2007

Pressures (gauge)Pressure drop = 0.792 bar

Velocity StreamlinesMaximum velocity = 398 m/s

Chris Densham UKNF 3rd Oct 2007

Options for T2K upgrade to Superbeam

• Window: should be OK if increased power is gained by increasing rep rate.

• Target: Static target difficult beyond 1 MW beam power – problems include:– Power dissipation– Thermal stress– Radiation damage– High helium flow rate, large pressure drops

• Target: expect to replace target increasingly often as beam power increases

• New target technology seems necessary

Chris Densham UKNF 3rd Oct 2007

Open jets

Is there a ‘missing link’ target technology?

SOLIDS LIQUIDS

Monolithic Powder jets Contained liquidsSegmented

Chris Densham UKNF 3rd Oct 2007

Examples: fluidised jets of particles in a carrier gas

Chris Densham UKNF 3rd Oct 2007

Different fluidising technologies

www.claudiuspeters.com

Chris Densham UKNF 3rd Oct 2007

Powder jet targets: some potential advantages

• Shock waves– a near hydrostatic stress field develops in the particles so high

energies can be absorbed before material damage– Shock waves constrained within material – no splashing or jets as for

liquids– Material is already broken

• Heat transfer– A flowing powder provides high heat transfer opportunities so the bed

can dissipate high energy densities and total power (and perhaps more than one beam pulse)

– External cooling

• Solid vs liquid?– Carries some of the advantages of both the solid phase and of the

liquid phase: • metamorphic, can be shaped to suit• Pumpable• replenishable - as powder wears out or gets damaged

Chris Densham UKNF 3rd Oct 2007

Powder jet targets: some potential difficulties

• Erosion of material surfaces, e.g. nozzles• Activated dust on circuit walls (no worse than e.g.

liquid mercury?)• Activation of carrier gas circuit• Achieving high material density – typically 50%

material packing fraction for a powdered material

Chris Densham UKNF 3rd Oct 2007

Some existing solutions to the erosion problem

Turbulent energy dissipation

Specially designed gravity fed heat exchangers

Chris Densham UKNF 3rd Oct 2007

Could a flowing powder or powder jet be a useful target technology?

For a T2K upgrade or another Superbeam e.g. SPL

• Obvious material for T2K would be graphite powder

• But 50% material would reduce pion yield• How about titanium powder?• Density of titanium powder may be similar to

solid graphite, ie 50% ρTi ≈ ρgraphite

For a Neutrino Factory target• Tungsten powder obvious candidate

–> the rest of this talk

Chris Densham UKNF 3rd Oct 2007

Schematic outline of a powder jet as a NuFact target

solenoid

W powder jet

He flow

beam

Pionshower

Chris Densham UKNF 3rd Oct 2007

Neutrino Factory Study II Target station layout

• W powder jet target roughly compatible with mercury jet target station layout – replace Hg pool with W powder receiver

Chris Densham UKNF 3rd Oct 2007

Neutrino Factory Study II Target station layout

• W powder jet target roughly compatible with mercury jet target station layout – replace Hg pool with W powder receiver

W powder

AIR LIFT

POWDER JET

NOZZLE

RECEIVER

POWDER COOLER

GAS COOLER

EXHAUSTER

COMPRESSOR

GAS

POWDER

FLUIDISED PRODUCT

Powder jet target plant - outline layout

SOLENOID BORE MIMIC

Chris Densham UKNF 3rd Oct 2007

AIR/PRESSURE IN

POWDER IN

JET GENERATION

AIR EXTRACTION/ VACUUM LIFT

DENSE MATERIAL FLOW ~1m

AUXILIARY AIR INPUT (NOT

NEEDED)

Powder jet prototype test plant - layout used in experiment

AIR IN

Chris Densham UKNF 3rd Oct 2007

The first day’s experiment18th July 2007

• Tungsten powder < 250 µm particle size• Discharge pipe length = 1 m• Pipe diameter = 2 cm• 3.9 bar (net) pneumatic driving pressure

Chris Densham UKNF 3rd Oct 2007

The first day’s experiment18th July 2007

• Tungsten powder < 250 µm particle size• Discharge pipe length = 1 m• Pipe diameter = 2 cm• 3.9 bar (net) pneumatic driving pressure• Approx. 10 m/s and c. 18% material by volume

achieved

Chris Densham UKNF 3rd Oct 2007

The second day’s experiment30th August 2007

• Tungsten powder < 250 µm particle size• Discharge pipe length = 1 m• Pipe diameter = 2 cm• 3.9 bar (net) pneumatic driving pressure• Vacuum lift to recirculate powder• Co-axial return air flow at entry of jet into mimic

of solenoid bore

Chris Densham UKNF 3rd Oct 2007

The second day’s results:

(Thanks to EPSRC Intrument Loan Pool for use of a high speed video camera)

2

cm

30 cm

Chris Densham UKNF 3rd Oct 2007

P0= 4.9 bar (abs)

P1= 1 bar (abs)

Initial bulk density

= 8660 kg/m3

= 45 % W (by volume)

Jet bulk density (approx. results):

~ 5000 kg/m3

~ 25 % W by vol.

(~ 2.5 x graphite density)

Jet velocity = 7-15 m/s

(100 kg in 9 seconds)

Tungsten powder jet – second day’s results

Chris Densham UKNF 3rd Oct 2007

NB 1: Calculation is for 10 GeV protons

NB 2: Calculation is for total yield from target ie capture losses excluded

MARS calculation of muon and pion yield from

(i) solid W and

(ii) 50% density W

by John Back, Warwick University

Chris Densham UKNF 3rd Oct 2007

• Improve bulk density of jet (-> 45% by volume?)– 18% -> 25% achieved by co-axial air flow - DONE– By changing discharge pipe length?– By incorporating porous (sintered) material into

discharge pipe?– By use of a nozzle?

• Demonstrate shock waves are not a problem– Possibility to use test facility planned at ISOLDE for

shock wave experiment on a powder sample – as for the mercury thimble experiment (Jacques Lettry)

• Demonstrate magnetic fields/eddy currents are not a problem– Use of high field solenoid (post MERIT – collaboration

with CERN + Harold Kirk?)

Powder jet: next stages

Chris Densham UKNF 3rd Oct 2007

Questions (mine) and requests

• Is a powder jet target of maximum density < 50% volume density an interesting or serious contender for either:– A Superbeam (e.g. graphite or Ti powder for T2K

upgrade?)– A Neutrino Factory (e.g. W)?– NB multiple bunches interacting with same material

should be OK

• If so, what are roughly optimal parameters for e.g. W powder NuFact target? MARS help requested.

• Could a contained pipe flow be used? – Necessary for T2K Superbeam, possible for NuFact? – (NB problems of window and 2ndary heating of pipe to

be addressed)

Chris Densham UKNF 3rd Oct 2007

Questions (yours)?

Chris Densham UKNF 3rd Oct 2007

Some porous sintered materials used in fluidised bed technologies