Alessandro Variola

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ESGARD OMNIA Meeting10/09/2007

• JRA
• Polarised Positron Sources

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Polarised Positron Sources

• Framework Future lepton colliders need positron
  sources !!!
• The important requirements in peak currents imply
  extremely high performances that are much more
  demanding
• SLC 0.6 mA - 4 kW deposited in the target
• LEP (LIL) 3 mA - 0.6 kW deposited in the
  target ILC 40 mA -
  5 kW deposited in the target
• DAFNE 2 mA - 0.5 kW deposited in the target
  ILC (conventional) gt
  28 kW
• KEKB 0.5 mA - 2 kW deposited in the target
  CLIC new 10 mA gt
  Conventional 16 kW
• LAL 0.8 mA - 0.8 kW deposited in the target
• Positron source performances lt electron sources
  Many parameters of the collider (also in the
  electron arm) are imposed by the quality of the
  positron source !!
• Positron production efficiency e electron
  driver e conversion e capture need for
  extremely performing electron beams, high thermal
  dissipation in converters, optimised capture
  section (linked with the whole machine)
• Physics case for polarised positrons already
  illustrated (see for example Moortgat-Pick, G. et
  al The role of polarized positrons and
  electrons in revealing fundamental interactions
  at the Linear Collider. ArXiv High Energy Physics
  - Phenomenology e-prints arXivhep-ph/0507011).
• Advantage of polarised positron source vs
  conventional pair creation in the converter
  only by high energy gammas. No charged particles.
  Thermal constraints strongly reduced.
• Disadvantage need for a lot of gammas.and RD
  too
• Most components of the colliders project are
  based on established technologies (need for D
  only). Polarised positron sources imply
  completely innovative schemes (undulators at 150
  GeV, Compton scattering _at_ 1-2 GeV with MW class
  optical devices) that need important RD programs
  to be validated.
• I hope that I managed to convince you that
  positron sources are critical for future lepton
  colliders projects and that polarised is better !!

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Two main lepton collider projectsCLIC ILCAnd
two different techniques to produce polarised
positrons Undulator and Compton
CLIC 2007 (3 TeV) ILC (Nominal)
Energy E GeV 9 150
Bunch population N 109 4 - 4.1 20
Nb bunches / train nb - 311 2625
Bunch spacing Dtb ns 0.667 (8 RF periods) 369.2
Train length tpulse ns 207 968625
Emittances gex , gey nm, nm.rad 600, 10 8400, 24
rms bunch length sz mm 43 - 45 300
rms energy spread sE 1.5 - 2 1.5
Repetition frequency frep Hz 50 5
Beam power P kW 91 130
ILC (Already in EDR phase) Baseline solution
undulator Alternative Solution
Compton CLIC Preferred solution
Compton Analysed Solution Undulator
Both schemes are based on a drive high energy
beam (undulator 150 GeV Compton 1-2 GeV)
producing the gammas. These are
subsequently converted in polarised pairs in a
spinning target
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Critical aspects JRA for Polarised positron
sources

• Undulator Comptongt Instantaneous Energy
  deposition. Heating Target technology
• Undulator Length gt Prototype of new materials SC
  undulator. Higher B field
• Undulator mass production
• Compton High power, high frep fiber laser
• CW warm cavity for the capture section thermal
  dissipation
• Polarimetry and polarisation transport
• This JRA aims at solving these issues, at least
  the most important ones on this list (or even
  betterall of them).

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ESGARD feedback and present situation

• 1st Proposal presented on Compton Sources
• 2nd phase join also of the Undulator request. A
  big effort was spent in integrate the different
  activities.
• Feedback from the Directors meeting to be
  postponed (or fully included in Optional
  activities)
• Also if in Optional activities strong budget
  reduction requested (4.1 M total _at_ 33 refunding)
• We find unfair both decisions and
• We try to convince the community that the program
  is indispensable
• We will present our Priority (4.1 MEuros) and
  Option (1.5 MEuros) activities. We feel that,
  since we have already been penalised once (fully
  optional), the budget cut is not justified
  compared with other programs that have maintained
  a fraction of CORE activities. In the case that
  we will still remain in the Optional we want to
  go with our 5.6 MEuros Program.
• It is difficult for us to set up a clear scenario
  (JRA/WP) since it depends on the decision on
  funds availability

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JRA WP0 Management

• Managing the JRA program, work, reports and
  milestones
• Coordinate the communication between different
  institutes
• Ensuring the communication with the FP7 IA
  management and with the EU representatives.

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JRA WP1

• Priority
• Develop a high-power fiber laser and its
  associated digital feedback to be locked on a
  Fabry Perot resonator 564.500 (EU-funded). On a
  basis of the 33 EU refunding the total cost is
  1,693,500 .
• The expected outcomes are to develop a 200W
  continuous pulsed laser (Min. repetition
  frequency 40 MHz) and to lock it to a Fabry Perot
  cavity (Min. finesse 10000). This system should
  subsequently be installed in an accelerator
  complex (ATF/FLASH/CTF3/DAFNE Linac/ERLP) to test
  the gamma/x production.
• Participating labs LAL Orsay, IPN Lyon, LNF
  Frascati

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JRA WP2

• Priority
• Develop prototype of ILC positron source target
  consisting of a rapidly spinning wheel of
  titanium alloy in a strong magnetic field, with
  integral water cooling. Demonstrate mechanical
  stability under strong eddy current braking,
  reliability, and thermal control. The prototype
  would be developed jointly by STFC and University
  of Liverpool at Daresbury Laboratory.
• Cost to EU 420,000 with matching funds of
  1,310,000 giving a total cost of 1730,000 .
• Participating labs Liverpool, Daresbury
  Laboratory

UK Resources from STFC (LCABD, CI,
ASTeC) Approved by UK Project Manager, CI
Director, ASTeC Director
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JRA WP3

• Priority
• Develop short undulator prototype (40 cm) using
  more advanced materials (eg Nb3Sn) with the goal
  of generating significantly higher on-axis
  magetic fields and so reducing the overall length
  of the full ILC undulator by several tens of
  metres.
• Cost to EU 180.000 with matching funds of
  970,000 giving a total cost of 1,150,000 .
• Participating labs Daresbury Laboratory, RAL

UK Resources from STFC (LCABD, CI,
ASTeC) Approved by UK Project Manager, CI
Director, ASTeC Director
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JRA WP4

• Priority
• Polarization studies for alternative
  helicity-flipping schemes
• Spin tracking through targets (including magnetic
  and electric fields) and capture section
• Polarization studies on possible systematic
  uncertainties in the machine design
• Theoretical uncertainties from higher order
  corrections including spin effects
• Construction and test of a prototype for a low
  energy positron polarimeter (Bhabha polarimeter).
  It will be developed and tested jointly by DESY,
  Humboldt University, Tel Aviv University and
  NCPHEP Minsk
• Cost to EU 200,000 with matching funds of
  400,000 giving a total cost of 600,000 .
• Participating labs DESY, IPPP Durham, Humboldt
  University Berlin, Liverpool (?)

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JRA WP5

• Option
• Design and construction of a CW RF warm cavity
  with high gradient (100 kW dissipation). Study
  prototyping 250,000 (EU Funded) gt Total cost
  750,000 .
• This cavity is needed in the capture section
  since after the target and in a strong solenoidal
  field we cannot envisage the use of a SC CW
  cavity. The expected outcomes are to design and
  realise a CW warm cavity (frequency ranging from
  600 to 1500 MHz) with a gradient higher than 1.5
  MeV/m with 100 kW max dissipation. The cavity
  will be tested in (DAFNE/ATF).
• Participating labs LAL Orsay, IPN Lyon, LNF
  Frascati

UK Resources from STFC (LCABD, CI,
ASTeC) Approved by UK Project Manager, CI
Director, ASTeC Director
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JRA WP6

• Option
• For the ILC approximately fifty undulator modules
  will be required. It is essential that the
  present design is taken forward to a position
  where a contract can be placed with an industrial
  partner for this large quantity. The undulator
  concept will be value-engineered and the revised
  design prototyped and tested.
• Cost to EU 250,000 with matching funds of
  500,000 giving a total cost of 750,000 .
• Participating labs Daresbury Laboratory, RAL

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At present (hoping in positive evolutions)

• JRA Priority Activities
• 
  EU funding request Total
• -WP1 fiber laser
  564000 1693000
• -WP2 converter target prototype
  420000 1730000
• -WP3 undulator prototype
  180000 1150000
• -WP4 polarisation studies
  200000 600000
• 
  1364000 5173000
• JRA Option Activities
• -WP5 CW cavity
  250000 750000
• -WP6 undulator engineering 250000
  750000
• 
  500000 1500000
• TOTAL gt
  1864000 6673000

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Commitments of the funding agencies

• LAL-IN2P3 CNRS 4.6 FTE/year 4 Years. Approved
  by LAL Director
• IPN Lyon 0,5 FTE/year 4 Years (TBC)
• INFN 0,5 FTE/year 2 Years (TBC)
• LCABD (UK) UK Resources from STFC (LCABD, CI,
  ASTeC)
• Approved by UK Project Manager, CI Director,
  ASTeC Director
• STFC 3 FTEs/year 4 years
• U of Liverpool 2 FTEs /year 4 Years
• DESY 1FTE /year 4 years (tbc)
• Durham 0.1 FTE /year, TBA

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Apart form the colliders program medical and
industrial fallout

• Compton
• Low energy Compton scattering application by
  the others gt
• in the static and dynamic imaging (like 3D
  compressionless mammography and broncography),
• In K-edge radiography and therapy and in the
  catheterless coronary arteries angiography
• gadolinium based cancer therapy and blood imaging
  .
• x-ray diffraction protein crystallography
• The possibility to identify the atomic number of
  different materials with hard x rays open the
  way also for nuclear application of the Compton
  scattering.
• High penetration photons are also suitable for
  security and aerospace applications like for
  example the radiography of shielded material
  investigating the presence for small quantities
  of a particular nuclei.
• Undulator
• Knowledge exchange with industrial partner will
  enhance superconducting magnet manufacturing
  within EU
• Superconducting undulators could have major
  impact on all light sources and FELs

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Conclusions

• Positron sources are one of the most critical
  issues for the future generation of lepton
  colliders
• An international community is working to give an
  answer to the most delicate aspects
• We planned to suggest a JRA to have the
  possibility to develop, in this framework,
  important advancements.
• Work is essentially based on Undulator, Laser and
  Target tech.
• We estimate to have been penalised twice. 1)
  Optional activities 2) budget cut.
• We are asking to get back into the game trying to
  take into account as much as possible the
  suggested work plan
• In principle we would like to be considered at
  least in the Priority activity. Also the
  Option activities are important for the
  completeness of the program.

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• Thanks to all the collaborators that provide
  material for this presentation
• Thank you for your attention