ENG Meeting

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ENG Meeting Targets Collectors 26 March 2003 J
R J Bennett, RAL
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NOTES These overheads should be read in
conjunction with those of Helmut Haseroth (this
meeting) to see a more complete picture of
targets and collectors. A meeting of the Target
and Collector Group was held on the morning of 26
March. The subjects covered the present position
of targets and collectors. The overheads will be
available at the CERN muon website http//muonsto
ragerings.web.cern.ch/muonstoragerings/ This
talk gives a summary of the current situation.
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Meeting of Target and Collector Section, 26
March 2003, 9.30 am in Room 40-S2-B01. Programme
09.30 Introduction Roger Bennett 09.55
Mercury targets Adrian Fabich 10.20 Coffee
Break - 20 minutes 10.40 Solid granular
targets Peter Sievers 11.05 Rotating toroidal
targets Paul Drumm 11.30 Horns Simone
Gilardoni 11.55 Discussion 12.15 Close
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• Specification
• Proton Beam - Pulsed at 10-50 Hz
• Energy 2-30 GeV
• Average Power 4 MW

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• High Power Pulsed Targets
• Power Dissipation
• Neutrino Target
• mean power dissipation 1 MW
• pulse length 1-2 ms
• pulse repetition rate 50 Hz
• energy dissipated per pulse 20 kJ
• energy density 0.3 kJ/cm3
• Spallation Neutron Source Target
• mean power dissipation 1-10 MW
• pulse length 1 ms
• pulse repetition rate 50 Hz
• energy dissipated per pulse 20-200 kJ
• energy density 0.03 kJ/cm3
• p-bar target at Fermi Lab 6 kJ/cm3

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• The Importance of Target Studies
• The proton accelerator looks good
• The collection and cooling channel is
  inefficient but will work
• Know how to design a target for lower power
  dissipation - 100 kW
• The target is a potential Show Stopper

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Programmes under way The USA are building SNS.
The Japanese are active as well. LAL/Orsay are
developing Horns.
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Target Studies Continue with present lines of
study 1. Molten Metal Jets 2. Flowing Contained
Molten Metal (Probably not viable with the small
diameter required for a neutrino target) 3.
Helium Cooled Solid Spheres 4. Moving Solid
Targets or Rotating Band 5. New Ideas?
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• The Liquid Metal (Mercury) Jet
• The jet is constantly being reformed for every
  pulse. The jet becomes heated by the beam and
  disperses to hit the walls
• No Problems with
• Radiation Damage
• Shock Damage
• Power dissipation
• Possible Problems with
• Jet formation
• Interaction with the magnetic field
• Interaction of the mercury with other equipment
• Tests to date indicate that the jet is viable

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Granular Target Solid Metal Spheres in Flowing
Coolant P. Sievers, CERN This design is based
on a number of targets - which reduces the energy
density to a level where small spheres (2 mm
diameter) will not suffer from shock effects. The
targets are constructed from a matrix of spheres
and cooled by flowing a liquid (helium) over
them. This solves the problems of shock, but has
the disadvantages of diluting the target to make
space for the coolant and requiring the pion
beams from the several targets to be collected
and formed into a single beam.
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• A Water Cooled Cu-Ni Rotating Band Target (BNL
  and FNAL, Bruce King)
• A Radiation Cooled Rotating Toroid, (RAL)
• TOROID OPERATES AT 2000-2500 K
• RADIATION COOLED
• ROTATES IN A VACUUM
• VACUUM CHAMBER WALLS WATER COOLED
• NO WINDOWS
• SHOCK? Pbar target OK. Tests using electron beam
  simulation indicate no problem.

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V
V Lf R not fixed
No threading solenoid
Individual Targets Levitated
Reservoir for targets to collect and cool
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• Advantages of Solid Target
• No windows
• Cooling in the walls
• Simple concept
• Disadvantages
• Large rotating toroid or individual targets
• Problems if toroid breaks
• Thermal shock - toroid breaks
• Very radioactive

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• Pulsed Effects in Solid Target
• The thermal shock can exceed the mechanical
  strength of the material causing it to break.
• The pbar target at FNAL is OK at 10 times the
  pulse power density. The pbar target has
• 600-700 J/gm in nickel discs, DT per pulse (1.6
  ms) 1000 K
• (compare to 60 J/gm in the neutrino tantalum
  target)

Stack of slowly rotating discs
Gas cooling between discs
proton beam
pbar target
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Tests by RAL with electron beams show that
tantalum foils can withstand at least 200000
pulses and have lasted for 1000000.
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• OTHER PROBLEMS
• Magnet
• Target operates in a magnetic field, Forces,
  Induced Currents
• SC magnet (heat and radiation),
• Radiation and Safety
• Beam Dump - 1-4 MW! Spread the beam to make
  cooling easier.
• Radiation Shielding.
• Maintenance. Remote handling essential. Target
  changes.
• Disposal
• Safety requirement/legislation -formidable.

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Collector 1. Solenoid, 10-20 Tessla US
consider they have a long life (gt1 year)
design 2. Horn Problems with Heat
dissipation, Radiation damage, Stress
Possible 6 week life Studies will continue
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• EXCITING TIMES
• Challenge
• At the edge and beyond
• present knowledge
• New Ideas Required