WP2: Targets

Proposed Outline Work Programme

Chris Densham

Chris Densham

A few quotes from the EUROnu proposal:

1) “The target is probably the most difficult problem for both a Superbeam and a Neutrino Factory.”

2) “For a Superbeam facility, the integration of the target inside the horn has to be considered from the beginning of the project.”

3) “The work on the [neutrino factory] target is very similar to that for the Superbeam and will be undertaken in that [i.e. this] work package.”

-> Therefore, target options should be considered in terms of compatibility with both a Superbeam and a Neutrino Factory.

Chris Densham

Powers and power densities in a few target systems

Material Beam Power in targetkW

Peak power densityJ/cc/pulse

Pulse length

SPL-SB Heavy metal?

2.2/3.5 GeV protons

1000 200 0.5 – 2.2x10-3 s

T2K Graphite 30-50 GeV protons

30 344 5x10-6 s

Neutrino Factory

Hg jet or tungsten

8 -50 GeV protons

1000 300 Few x10-9 s

SNS

(J-SNS)

Contained Liquid Hg

1 (3) GeV protons

1400(1000) 10 (17) 1x10-6 s

GSI/FAIR Li or

Graphite

Heavy ions ?? 30000 5x10-9 s

Chris Densham

SPL-SB Baseline Schematic layout:

Neutrino Factory Baseline Schematic

layout:

Both baselines use liquid mercury jet target

Chris Densham

Pulsed beam interactions with mercury

MERIT experiment: Beam-induced splashing of mercury jet (c.200 J/cc)

- Damping of splashes due to magnetic field observed as predicted

- Analysis of MERIT data required

Cavitation damage in wall of Hg target container after 100 pulses of 19 J/cc proton beam (WNR facility at LANL)

Contained mercury

Free mercury jet

Chris Densham

Can a free mercury jet be combined with a magnetic horn?

• Magnetic horns are typically manufactured from aluminium alloy

• Mercury is commonly known to cause severe and rapid erosion of aluminum and its alloys

• Is it possible to protect a horn with a material compatible with liquid mercury? – If so, would the jet be ‘open’ or ‘contained’?

• Corrosion problem is in addition to the shock wave problem

• Combination of a mercury jet with a magnetic horn would appear to be extremely difficult

• Analysis of MERIT data necessary but not sufficient

Chris Densham

How about graphite targets? (pion+muon production for a neutrino factory)

MARS simulations by Harold Kirk

Graphite looks competitive with mercury for SPL beam energy (2-3 GeV)

Chris Densham

T2K graphite target design and installation within the 1st magnetic horn for T2K Phase 1 (750 kW beam, 30 kW deposited in target)

Max. helium velocity c.400 m/s

Chris Densham

Solid targets for Superbeams

• How high a power can a static graphite target dissipate for a Superbeam or a Neutrino Factory?– T2K phase 1 target power = 30 kW – c.f. 1000 kW on target for SPL-SB! – Static graphite target appears unfeasible for SPL-SB

• Is it possible to combine a moving target with a magnetic horn?

Chris Densham

Helium

Beam window

beam

Helium

Tungsten powder hopper

A flowing powder target for a Superbeam or Neutrino Factory?

Chris Densham

Tungsten powder open jet first results:

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

2

cm

30 cm

Chris Densham

Powder jet targets: some potential difficulties

• Erosion of material surfaces, e.g. nozzles, valves• 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

Outline Targets Programme

1) Contribution to interpretation of results of MERIT experiment.

This will answer many technical questions regarding liquid metal jet targets

2) Study of integration of mercury jets with a magnetic horn

3) Investigate ideas and limits for static and moving solid targets

4) Continue flowing powder target studies at RAL5) Begin studies of target integration with collection

system both for Nufact (solenoid) and for SuperBeam (magnetic horn)

6) Evaluate relative merits of different target options