MULTIMW TARGET DEVELOPMENT FOR EURISOL

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MULTI-MW TARGET DEVELOPMENT FOREURISOL
EUROTRANS
Y. Kadi A. Herrera-Martinez (AB/ATB) European
Organization for Nuclear Research, CERN CH-1211
Geneva 23, SWITZERLAND yacine.kadi_at_cern.ch
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Multi-MW Target Challenges

• High-Power issues
• Thermal management
• Target melting
• Target vaporization
• Radiation
• Radiation protection
• Radioactivity inventory
• Remote handling
• Thermal shock
• Beam-induced pressure waves
• Material properties

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Thermal Management Liquid Target with window
The SNS Mercury Target
Harold G. Kirk et al. (BNL)
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Thermal Management Liquid Target with window

• MEGAPIE Project at PSI
• 0.59 GeV proton beam
• 1 MW beam power
• Goals
• Demonstrate feasablility
• One year service life
• Irradiation in 2005

F. Groeschel et al. (PSI)
Proton Beam
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Thermal Management Liquid Target with window
F. Groeschel et al. (PSI)
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Thermal Management Liquid Target with free
surface
DG16.5 Hg Experiments nominal volume flow 10 l/s
BEAM

• Close to desired configuration
• intermediate lowering of level
• some pitting
• axial asymmetry

High-speed flow (2.5 m/s) permits effective heat
removal
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Thermal Management Target Pitting Issue
Before
ESS team has been pursuing the Bubble injection
solution. SNS team has focused on Kolsterizing
(nitriding) of the surface solution. SNS team
feels that the Kolsterized surface mitigates the
pitting to a level to make it marginally
acceptable. Further RD is being pursued.
After 100 pulses at 2.5 MW equivalent intensity
Harold G. Kirk et al. (BNL)
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Worldwide Programs
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Thermal Management radiation cooled rotating
toroidal target

• Distribute the energy deposition over a larger
  volume
• Similar a rotating anode of a X-ray tube

rotating toroid
toroid magnetically levitated and driven by
linear motors
R.Bennett, B.King et al.
solenoid magnet
toroid at 2300 K radiates heat to water-cooled
surroundings
proton beam
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Thermal Management JET
J.Lettry et al. (CERN)
TT2A
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Radiation Management
The SNS Target Station
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Radiation Management
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Radiation Management
The JPARC Kaon Target
18m
Concrete shield block
10m
Service space 2m(W)?1m(H)
Water pump
Iron shield
2m
T1 container
Concrete shield
Beam
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EURISOL Multi-MW Target
Objectives The objective is to perform the
technical preparative work and demonstration of
principle for a high power target station for
production of beams of fission fragments using
the mercury proton to neutron converter-target
and cooling technology similar to those under
development by the spallation neutron sources,
accelerator driven systems and the neutrino
factories. This high power target that will make
use of innovative concepts of advanced design can
only be done in a common effort of several
European Laboratories within the three
communities and their proposed design
studies. In this study emphasis is put on the
most EURISOL specific part a compact window or
windowless liquid-metal converter-target itself
while the high power design of a number of other
more conventional aspects are taken from the
studies in the other EURISOL tasks or even in
other networks like ADVICES, IP-EUROTRANS.
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EURISOL Target Stations

• 3x100 kW direct irradiation
• Fissile target surrounding a spallation n-source
• gt100 kW Solid converters (PSI-SINQ 740 kW on Pb,
  570 MeV 1.3 mA / RAL-ISIS 160 kW on Ta, 800 MeV
  0.2 mA / LANL-LANSCE 800 kW on SS cladded W, 800
  MeV 1.0 mA )
• 4 MW Liquid Hg (windowless or jet)

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EURISOL Hg-converter and 238UC2 target
60 kV
60 kV gt 2000º
Grounded lt 200º
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EURISOL Multi-MW Target
Participants
Contributor
P4 CERN P18 PSI Switzerland P19 IPUL
Latvia
C5 ORNL USA
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EURISOL Multi-MW Target
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EURISOL Multi-MW Target
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EURISOL Multi-MW Target
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Breakdown of work (per sub-task)
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Preliminary Studies

• Projectile Particle Proton
• Beam Shape Gaussian, ? 1.7 mm
• Energy Range 123 GeV
• Target Material Hg / PbBi
• Target Length 406080100 cm
• Target Radius 10203040 cm
• Spatial and energy particle distribution

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1 GeV Primary Proton Flux
1 GeV Proton range 46 cm

• The beam opens up to 20 degrees, with some
  primary back-scattering
• Primaries contained in 50 cm length and 30 cm
  radius

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Energy Deposition for 1 GeV protons

• Maximum energy deposition in the first 14 cm in
  the beam axis beyond the interaction point, 30
  kW/cm3/MW of beam ? dT/dt 14 K/s (Hg boiling
  point at 357 ºC)
• Energy deposition drops one order of magnitude
  at the proton range (46 cm)
• Large radial gradients (dE/dr 200) in the
  interaction region

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Neutron Flux Distribution for 1 GeV Protons
Radial
Front Cap
End Cap

• Neutron flux centered radially around 10 cm
  from the impact point
• Isotropic flux after 15 cm from the center,
  decreasing with r2
• Escaping neutron flux peaking at 300 keV
  (evaporation neutrons), with a 100 MeV component
  in the forward direction (direct knock-out
  neutrons)

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Neutron Energy Spectrum vs Fission Cross-Section
in Uranium

• Very low fission cross-section in 238U below 2
  MeV (10-4 barns). Optimum neutron energy 35 MeV
• Alternatively, use of natural uranium fission
  cross-section in 235U (0.7 wt.) for 300 keV
  neutrons 2 barns
• Further gain if neutron flux is moderated

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Alternative Target Configurations
Standard Configuration
Alternative Configurations
Reflector?
UCx Target
Reflector / UCx Target
Protons
Protons
Hg Target
Hg Target
Deuterons
UCx Target
Reflector / UCx Target
UCx Target
Reflector?
Low-Z Filter (?)
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Alternative Target Configurations
Alternative Configurations
Reflector / UCx Target
Protons
Hg Target
Deuterons
Reflector / UCx Target
UCx Target
Low-Z Filter (?)

• Increasing HE neutron flux through the End-Cap
  with decreasing Hg target length
• Increasing charged-particle and photon escapes
  with decreasing Hg target length
• Possible use of a low-Z filter to tune the
  average neutron energy to 35 MeV (maximise
  fission probability in 238U)

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Neutron Balance Density for 1 GeV Protons
Neutral balance boundary
Neutron absorbing region
Neutron producing region

• Neutron absorbing region 6 cm behind the
  interaction region, following the primary
  particle distribution
• Neutron producing region extending to the end of
  the target
• Small contributions from regions beyond the
  proton range
• Neutron producing region not extending beyond r
  1013 cm

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2 GeV Primary Proton Flux
2 GeV Proton range 110 cm

• Forward peaked primary distribution at 10
  degrees
• No back-scattering and rare radial escapes
• Few end-cap escapes
• 2?10-3 escapes/primary with an average energy of
  1 GeV for 80 cm
• 2 ?10-5 escapes/primary with an average energy
  of 0.7 GeV for 100 cm

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Energy Deposition for 2 GeV protons

• Largest energy deposition in the first 18 cm
  beyond the interaction point, 16 kW/cm3/MW of
  beam ? dT/dt 8 K/s (40 lower compared to the
  use of 1 GeV primary protons)
• Identically, smaller radial gradient in the
  interaction region (dE/dr 100)

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Neutron Flux Distribution for 2 GeV Protons
Neutron Yield (2 GeV proton) 57 77 n/p

• Neutron flux centered radially around 15 cm
  from the impact point, presenting a
  forward-peaked component
• Escaping neutron flux peaking at 300 keV, with
  a 100 MeV component in the forward and radial
  directions and few 1 GeV neutrons escaping
  through the end-cap
• Harder neutron energy spectrum and higher flux
  and in the target compared to the 1 GeV case

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Neutron Balance Density for 2 GeV Protons

• Increase in the relevance of the axial region in
  the neutron production
• Neutron producing region still not extending
  beyond r 10 13 cm
• The neutron capturing region gains relevance
  (6?10-4 bal/cm3/prim) compared to 1 GeV (6?10-5
  bal/cm3/prim)
• Significant reduction in neutron captures (one
  order of magnitude) by reducing the radius to 20
  cm

Neutral balance boundary
Neutron absorbing region
Neutron producing region
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3 GeV Primary Proton Flux
3 GeV Proton range 175 cm

• The beam opens up to 8 degrees, no
  back-scattering and few radial escapes (even for
  20 cm radius)
• Some primaries escapes through the end-cap ( 5
  ?10-5 escapes/primary)
• Average energy of the escaping protons 750 MeV

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Energy Deposition for 3 GeV protons

• Largest energy deposition in the first 22 cm
  beyond the interaction point, 12 kW/cm3/MW of
  beam ? dT/dt 6 K/s (60 lower compared to the
  use of 1 GeV primary protons)
• Smaller radial gradient in the interaction
  region (dE/dr 50) compared to the 1 GeV case

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Neutron Flux Distribution for 3 GeV Protons
Neutron Yield (3 GeV proton) 82 113 n/p

• Neutron flux centered radially around 20 cm
  from the impact point, with a larger
  forward-peaked component
• Escaping neutron flux peaking at 300 keV, with
  a 100 MeV component in the forward and radial
  directions and some 1.5 GeV neutrons escaping
  through the end-cap
• Slightly higher neutron flux in the target
  compared to the 2 GeV case

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PbBi Alternative 1 GeV Primary Particles
1 GeV proton range in Hg 46 cm
Hg
1 GeV proton range in PbBi 60 cm
PbBi
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PbBi Alternative Energy Deposition
Maximum energy deposition 30 kW/cm3/MW of beam
Hg
Maximum energy deposition 21 kW/cm3/MW of beam
PbBi
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PbBi Alternative Neutron Flux
Hg
PbBi
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PbBi Alternative Neutron Balance
Hg
Neutron absorbing region
Neutral balance boundary
Neutron producing region
PbBi
Neutron producing region
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PbBi Alternative Neutron Spectrum
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Summary of the Results

• Optimised for neutron production
• Radius 10 15 cm target radius from neutron
  balance point of view is enough
• Length Extend to the proton range to maximise
  neutron production and avoid charged particles in
  the UCx
• Energy Spectrum of the neutrons
• Dominated by the intermediate neutron energy
  range ( 20 keV - 2 MeV)
• Harden neutron spectrum by reducing the target
  size (but reduce yield and increase HE charged
  particle contamination)
• Use of natural uranium to take advantage of the
  high fission cross-section of 235U in the
  resonance region ? Improvement thorough neutron
  energy moderation
• Alternatively, axial converter-UCx target
  configuration for depleted uranium target
• Very localised energy deposition, 20 cm from the
  impact point along the beam axis 30 kW/cm3/MW of
  beam power, reduced with the increasing proton
  energy
• Possibility of using PbBi eutectic to improve
  neutron economy and reduce maximum energy
  deposition

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Future Work

• Optimise the energy deposition once the size is
  fixed
• Study the effect of the shape of the beam
  (parabolic, annular, variations in the sigma of
  the Gaussian distribution)
• Activation of the target (calculate the
  spallation product distribution)
• Model the fission target (including
  moderator/reflector) and optimise the fission
  yields
• Analyse alternative target disposition to
  improve the fission yields
• Study the use of deuterons as projectile
  particle