Outstanding issues for a Mercury Beam Dump

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Outstanding issues for a Mercury Beam Dump

• Tristan Davenne
• STFC Rutherford Appleton Laboratory, UK
• UKNF meeting
• Lancaster University
• 23rd April-2009

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Mercury beam dump design from NUFACT Feasibility
Study
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Mercury beam dump design from NUFACT Feasibility
Study
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Fluka Simulation - Energy deposition in mercury
pool 24 GeV beam
How much of the beam energy is absorbed in the
beam dump?
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Agitation eruption of mercury pool surface due
to 24GeV proton beam Autodyne simulationSplash
following pulse of 20Terra protons
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Autodyne simulation - Fluid Structure
interactionDamage to underside of 15mm stainless
steel plate
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Thermal shocks and magnetohydrodynamics in
highpower mercury jet targetsJ Lettry, A
Fabich, S Gilardoni, M Benedikt, MFarhat and E
Robert
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Damage as a result of high speed impact of a
mercury dropletStainless Steel vs. Ti-6Al-4V
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Splash mitigationConsider helium bubbles in beam
dump to reduce splash velocity
Proton beam
helium
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Mercury beam dump design from NUFACT Feasibility
Study
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Agitation of mercury pool surface due to
impinging mercury jet
2 phase CFX model mercury jet velocity 20m/s
Angle 5.7 mercury pool surface area 0.05m2
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Conclusions

• Simulations show that mercury splashes with a
  velocity of 75m/s will result when a pulse from
  the undisrupted 24GeV beam is absorbed by the
  mercury beam dump.
• (Mercury splash velocity of 30m/s has been
  observed experimentally when a 1GeV proton beam
  interacted with a trough of mercury. Lettry et
  al.)
• A 3mm diameter mercury droplet impacting a
  stainless steel plate at 75m/s is predicted to
  cause significant damage. Ti-6Al-4V is
  predicted to be more resistant to damage due to
  higher ultimate strength and shear strength.
• Significant agitation of the mercury surface also
  results from the impingement of the mercury jet.

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Outstanding Issues

• Is there space inside the solenoid to house a
  large enough mercury beam dump? (Must consider
  fluctuating mercury level as a result of mercury
  jet and proton beam.)
• How much shielding required? (Superconducting
  materials have very low heat capacity so need to
  ensure beam energy is captured in the dump and
  shielding.)
• What material should the inside surfaces of the
  beam dump and solenoids be made of? (Material
  selection critical in terms of resistance to
  pitting)
• Is an active mitigation device desirable to
  reduce the splash that results from the proton
  beam interaction? (sprung baffles, helium bubbles
  etc)

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Instantaneous Energy Deposition

• Result of instantaneous energy deposition
• Increase in temperature causes pressure rise
• (analagous to Youngs Modulus linear relationship
  between stress and strain)
• 2. Strain energy is built up in the fluid due to
  compression (area under graph)
• Ref (Sievers Pugnat)
• 3. Strain energy will be released as kinetic
  energy
• 4. Expansion velocity is proportional to energy
  deposition

Sievers Pugnat 2000 considered a parabolic
radial energy deposition in 2cm diameter mercury
target and reported a radial velocity at surface
of mercury jet due to proton beam is 36m/s
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Autodyne Model of Merit Jet beam energy
24GeVbunches in a pulse 4pulse duration
2.3ustotal energy deposition in mercury in a
pulse 8kJ
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Autodyne Model of Merit Jet Beam at 33mrads to
10mm diameter mercury jet
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Autodyne Model of Merit JetMax radial Velocity
93m/s