Target%20Station%20and%20Target%20Damage%20Session%20-Introduction-

1
Target Station and Target Damage
Session-Introduction-

• I. Bailey
• University of Liverpool /
• Cockcroft Institute
• RAL September 27th 2006

2
Session Outline

• 1100 Introduction (20 min) - Ian Bailey
• 1120 Target damage simulations (15 min) - Andriy
  Ushakov
• 1135 Discussion (45 min) - All
• 1220 Alternative target design status (5 min) -
  Ian Bailey
• 1225 New results for crystallized W target from
  KEK (10 min) - Masao Kuriki
• 1235 Discussion (10 min)- All

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Undulator-Based Positron Source for ILC

• The ILC requires of order 1014 positrons / s to
  meet its luminosity requirements.
• A factor 60 greater than the conventional SLC
  positron source.
• Undulator source should have lower stresses in
  the production target(s) and less activation of
  the target station(s) compared with a
  conventional source.
• Collimating the circularly-polarised SR from the
  undulator leads to production of
  longitudinally-polarised positrons.

4
ILC Positron Source Layout
EUND - undulator TAPA - target station A TAPB -
target station B
Baseline layout of ILC with undulator at 150GeV
position in main linac.
Not to scale in any dimension!
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Undulator Photon Beam (BCD)

• Assume K1, 1cm period, 100m long undulator.
• Assume nominal ILC e- bunch structure.
• Neglect collimation.
• Target 450m downstream of undulator.
• Total photon beam power 145 kW
• Average photon energy 13MeV
• Beam spot rms 1.5 mm (0.75mm in BCD)

Simulations using SPECTRA
10MeV photons
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Undulator Photon Beam (2)
Target designed for 300kW average photon beam
power.
? Proportional to undulator length
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Target Project Overview
The University of Liverpool heads a
EUROTeV-funded task to carry out design studies
of the conversion target and photon collimator
for the polarised positron source.
Capture Optics
Positron beam pipe/ NC rf cavity
Target wheel
Photon beam pipe
Motor
Vacuum feedthrough
LLNL - draft design

• Working in collaboration with SLAC and LLNL.
• Developing water-cooled rotating wheel design.
• 0.4 radiation length titanium alloy rim.
• Radius approximately 1 m.
• Rotates at approximately 1000 rpm.

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Target Station Systems and Groups

• LLNL
• Target design
• Computational studies
• SLAC
• Integration
• Radiation studies
• Liverpool / DL / RAL
• Target design / prototyping
• DESY
• Target performance modelling
• Cornell /BINP / KEK
• Alternative target
• ANL
• Source modelling

• Approx 400 m downstream of undulator
• Key sub systems
• Target wheel
• Drive system
• Cooling system
• Vacuum system (10-8Torr)
• Remote-handling system
• Diagnostic and control systems
• Target support systems
• Photon collimator
• Photon beam dump
• Capture optics
• NC rf cavity

9
Target Wheel Design
Numbers refer to LLNL study of earlier solid-disc
design.

• Constraints
• Wheel rim speed determined by thermal load and
  cooling rate
• Wheel diameter determined by radiation damage and
  
• Materials fixed by thermal and mechanical
  properties and pair-production cross-section

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Power Deposition Cooling
Approximately 10 of photon beam power is
deposited in target wheel (30kW)
Water fed into wheel via rotating water union on
drive shaft.
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Target Wheel Design

• Recent drawings from DL design team
• 5 spokes (following LLNL vibrational studies)
• Thicker inner region to allow for stability,
  easier manufacture and balancing
• Scaled to 1m diameter
• LLNL may also extend driveshaft through vacuum
  chamber on both sides to allow separation of
  water union and drive system and prevent
  deflection of wheel in AMD field.

12
Radiation Effect Issues

• Material Damage
• Need further analysis to gain confidence in
  numbers from earlier work.
• Currently investigating options for this work.
  Damage to nearby components (motors, seals, etc)
  needs to be checked.
• Material Activation
• Analysis needs to be done on this for handling
  issues as well. Planning to have this done by
  whoever does the damage assessment. Needs to
  include looking at cooling fluid (water, liquid
  nitrogen). Possibly will need to include
  filtration on nitrogen loop to remove carbon
  decay products (soot).

Provisional list from Tom Piggott, LLNL
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Neutron Production
See Target Hall Design and Activation session
From TESLA study, expect 100mSv/h activation in
target region. EU exposure limit for radiation
workers is 20mSv/year
V. Bharadwaj - Positron Source Workshop,
Daresbury 2005
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Mechanical Design Issues

• Thermal Modeling
• Complete modeling to check earlier results with
  varying beam parameters as well as varying wheel
  diameter and speed.
• Structural Modeling
• Complete structural modeling for various cases
  analyzed thermally. Continue with vibration
  analysis, check internal modes, probably change
  to an odd number of spokes to avoid possible
  problems.
• Repetitive Loading
• Check for effects of repetitive loading from
  beam, fatigue, creep, etc. Confer with
  metallurgist at LLNL.
• Shaft Orientation/Deflection
• Evaluate moving to shaft supported on both ends.
  Possible vacuum seal issues, but simplifies
  motor and water union mounting. Evaluate
  movement of wheel under load conditions. Some of
  this already done with vibration modeling.
• Wheel Size
• Evaluate thermal/structural/radiation damage
  limitations on wheel diameter. Also include
  looking at limitations imposed by other system
  components (capture optics, etc).
• Target Station Handling
• Evaluate remote handling possibilities. Also
  look at packaging of target station to allow easy
  removal, and possible motion of target to move
  beam to extend target life.
• Vacuum Design
• Requirements for vacuum in target station is
  determined by amount of differential pumping
  possible between the downstream accelerating
  cavity and the target station itself. Vacuum
  simulations /calculations required to determine
  achievable vacuums given outgassing from target
  seal leakage.
• Cooling System Design
• Layout and specification for target wheel
  cooling as well as AMD cooling system (and photon
  collimator?)
• Piping/Electrical Layout
• Instrumentation and controls
• Layout and specification of needed
  instrumentation and controls.

Provisional list from Tom Piggott, LLNL
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AMD Related Issues
Provisional list from Tom Piggott, LLNL

• AMD Design
• Further evaluation of pulsed/continuous design.
  Look in more detail at cooling and stress issues.
• Magnet Loading on Wheel
• Try to bring simulations and experimental data
  closer. Look at required motor power, additional
  heat input.

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Integration Issues
Provisional list from Tom Piggott, LLNL

• Integrated Simulations
• Changes to undulator and collimator designs alter
  thermal load requirements of target. Effect of
  evolution in target / AMD design needs to be
  related to yield and polarization of finally
  captured positrons.

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Eddy Current Simulations
See AMD Session

• Initial Maxwell 3D simulations by W. Stein and
  D. Mayhall at LLNL indicate
• 2MW eddy current power loss for 1m radius solid
  Ti disc in 6T field of AMD.
• lt20kW power loss for current 1m radius Ti rim
  design.
• However - Simulations do not yet agree with SLAC
  rotating disc experiment.
• 8 diameter Cu disc rotating in field of
  permanent magnet.
• Possibility of OPERA-3D simulations at RAL.

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Other Issues
Provisional list from Tom Piggott, LLNL

• Other Target Technologies
• Stay aware of developments regarding alternative
  target materials, radiatively-cooled targets,
  liquid metal targets, etc.
• Other Positron Source Technologies
• Stay aware of developments regarding conventional
  and Compton scattering sources.

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UK Plans

• Prototyping to demonstrate
• Stability of rotating target
• Reliability of drive mechanism and vacuum seals.
• Rotation of target in B field of capture optics.
• Reliability of water-cooling system for required
  thermal load (average / peak?)
• Engineering techniques for manufacture of
  water-cooling channels.

• Liverpool, DL, and RAL plan to further develop
  the LLNL design and build prototypes of the
  target systems to determine the reliability.
• Bid submitted to PPARC as part of LC-ABD.
• Further EU funding? Coordination needed with
  other positron souce projects (CLIC) through
  ELAN, EUROTeV, etc.

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UK Proposed Milestones

• Goal 3. Construct and test a prototype to
  establish the mechanical stability of the target.
• 3.1 Jul 07 - Infrastructure in place at Daresbury
  Laboratory.
• 3.2 Aug 07 - Design of target test rig and
  instrumentation complete.
• 3.3 Oct 07 - Construction of target test rig
  complete.
• 3.4 Oct 07 -Construction of first prototype
  complete.
• 3.5 Apr 08 -Testing of first prototype complete.
• 3.6 Jun 08 - Data from first prototype analysed.
• Goal 4. Construct and test a prototype to
  demonstrate operation of target in strong
  magnetic field.
• 4.1 Nov 07 - Magnet design complete.
• 4.2 Mar 08 - Magnet construction complete.
• 4.3 Sep 08 - Construction of second prototype
  complete.
• 4.4 Mar 09 - Testing of second prototype
  complete.
• 4.5 May 09 - Data from second prototype analysed.
• Goal 5. Construct and test a prototype to
  establish performance of the target cooling
  system.
• 5.1 Feb 08 - Possible technologies for simulating
  thermal load identified.
• 5.2 Jun 08 - Design of thermal load source and
  interface complete.
• 5.3 Mar 09 - Installation of thermal load in test
  rig complete.
• 5.4 Jun 09 - Construction of third prototype
  complete.
• 5.5 Jan 10 - Testing of third prototype complete.

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Discussion

• Whats missing from the RD list?
• Are all topics covered?
• Is the proposed prototyping programme sufficient
  / necessary?
• Do we have enough faith in radiation damage
  simulations to opt for smaller target wheel?
• Scope for further collaboration / cooperation

• Alternative targets discussed later in session