ILC Positron Source WS. Report

Transcription

1 ILC Positron Source WS KURIKI Masao ILC Positron Source WS Report KURIKI Masao Contents 1)ILC Positron UK 2)Review of talks 3)Summary Powered by 20 April

2 ILC Positron Source WS KURIKI Masao ILC Positron UK Daresbury laboratory in UK. Over 40 participants from Japan, US, and European countries. Many issues on undulator, conventional, and Compton schemes were discussed. A framework is decided A report describing proposed schemes will be made untill (or before) Snowmass. Discussion will be made based on this report. A baseline and option(s) will be decided according to this discussion. 20 April

3 ILC Positron Source WS KURIKI Masao The ILC parameters and the demands on the positron source Nick Walker DESY Workshop on Positron Sources for the ILC CCLRC Daresbury Lab 11th April April

4 GDE Goal for 2005 ILC Positron Source WS KURIKI Masao Arrive at an internationally agreed upon BASELINE CONFGURATION by end of Baseline configuration will form blue print for CDR+$ due end 2006! Snowmass Workshop ( ) critical to this process we must attempt to agree on basic parameters by end of workshop Remainder of year will be needed to document decisions parameter sets basic layouts lattice files etc Aggressive schedule makes this workshop critical! 20 April

5 Polarisation ILC Positron Source WS KURIKI Masao Undulator-based source currently seems the most viable option [my opinion] Questions have been raised over impact on operations and commissioning particularly during early turn-on phase One scenario: begin with conventional source (non-polarised) Upgrade to undulator (polarised) source at a later date 20 April

6 The Choice of Baseline Configuration Conventional Undulator Snowmassend 2005? baseline end 2006 C D R ILC Positron Source WS KURIKI Masao 2008? T D R options Compton GDE change control board 20 April

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16 Review of Target Thermal Damage Workshop on Positron Sources for the International Linear Collider 11 April 2005 Toshihiro Mimashi, KEK

17 Biggest issue in this Workshop A Conventional positron source? Or Undulator Based Positron Source? Target Thermal Damage is the one of the key points

18 What we want to know about target thermal damage. One bunch beam may give a damage to the target? (spot size) Bunch Overlap Limit (rotating speed) Time distance limit (# of target in multi target system)

19 To avoid damage of Positron Target Material A high heat capacity A low coefficient of thermal expansion A high ratio of yield strength A Large material yield stress Increase spot size of the incident beam Multi Target System Rotate Target to avoid individual pulses imping on the same spot Liquid Target

20 Target Material (1) Target Material High Z targets Cross section Z2/A High melting point Strong Strength Higher positron yield Tantalum Tungsten Rhenium Iridium

21 Other Material? Poisson s ratio ( ) σ = α /[ 2( 1µ )] T ET ZrW O 2 8 Maximum Stress Young s modulus Thermal expansion coefficient Target temperature rise 2 T( 2 N /r C ) de /dx p W 20 Ta 12 Mo z 1. 1ln( Ee )3. 9 max αt 0

22 Liquid lead target From PAC2001 proceedings, Liquid Metal Target for NLC Positron Source By T. Vsevolozhskaya, et.al

23 ILC Positron Source WS KURIKI Masao ILC Positron Project At KEKB IPPAK(一泊) The positron production target hardness is examined by injecting electron bunches stored in KEKB at the beam dump. KEKB mode : Reproduce the energy density of the ILC target with the KEKB normal operation. ILC mode : Reproduce the energy density and the flux by modifying the bunch fill pattern and the abort kicker. 20 April

24 ILC Positron Source WS KURIKI Masao Treasure Hunting W-Re alloy is the best candidate as the target material, but it is hard to obtain as ingot. Pure W is considered to be a possible replacement. Vinod (SLAC) has kept a W-Re ingot as a memorial paper-weight. He will give it us. Geometry is in 2.5inc(6.25cm) diameter, 20mm thickness. 4 or more targets can be made from the ingot. 20 April

25 Undulator Based Positron Source Issues Jim Clarke ASTeC Daresbury Laboratory

26 Planar Undulators Period ~ 14 mm K~1 B ~ 0.75 T L ~ 100 m Gap ~ 5 mm Conventional permanent magnet solution straightforward Less demanding than X-FEL undulators in terms of field quality Access at sides for magnet measurements, diagnostics, pumps etc Available from industry today

27 Polarised Positrons Use circularly polarised light to generate polarised positrons Generate this light with a helical magnetic field Several permanent magnet helical undulators have been installed on light sources now mainstream technology For ILC can use circular beam pipe and so generate higher on axis fields than light source undulators Circular pipe also well suited to superconducting helical designs Helical Undulators give a higher flux anyway regardless of polarisation

28 Possible Designs for ILC Helical Undulator 7 On Axis B Field (T) Need a short period more periods more photons more positrons Two competing designs both 14mm period and ~4mm beam aperture: Required B Field to Produce 20 MeV Photons Undulator Period (cm) Super-Conducting Bifilar helix Permanent Magnet Ring undulator 2.9

29 Winding Geometry Material: Al 314 * 20 periods of double-helix Winding cross section: 4*4 mm2 29

30 Achieving a Vacuum in the undulator vessel To achieve ~10-8 mbar at room temperature will require a NEG coated vessel Standard NEG coating techniques impractical for a 4mm circular aperture vessel Vacuum Science R&D required Possible coating techniques are being investigated with Manchester Metropolitan University collaboration Superconducting magnet will be a cryopump so NEG not needed But vacuum level achieved in both schemes will be limited by synchrotron radiation hitting the vessel and desorbing molecules Calculations of SR in near field and at large angle important

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35 F. Zomer Orsay LAL/IN2P3 CNRS Daresbury 11 13/04/05 Fabry Perot cavity & pulsed laser Klaus s talk: LASER: 1ps pulsed with ~ ~300MHz & Smallest beam waist Solution: Concentric Fabry Perot resonator in pulsed regime

36 R&D to match Klaus s requirement Moderate cavity gain (Urakawa et al. KEK) Very small laser beam waist ( 5µm) to increase de laser e luminosity 4 mirrors cavity High input laser power KEK R&D Very high cavity gain Moderate laser beam waist ( 50µm) 2 mirrors cavity Concentric cavity Moderate input laser power Orsay (Eurotev) R&D

37 Possible laser for Klaus s scheme Opt. & Phot. News 2003 Yb:YAG, 33MHz 1.7µJ/pulse { 105 (cavity) 0.1J/pulse}

38 Experience of Remote Handling of a Proton Beam Target Tim Broome, ISIS Facility Rutherford Appleton Laboratory

39 Guiding Principles (1) All components that have a limited lifetime must be exchangeable within a reasonable time. (Within natural scheduled shutdown periods.) All components that can be designed for facility life must still be exchangeable as long as chance of failure theoretically exists; longer shut down time is acceptable. Allow either complex repair inside the target station or limit handling to exchange of pre manufactured modules. Non exchangeable components should be limited to carefully justified cases. These considerations will determine the overall design of the handling facilities

40 Guiding Principles (2) Handling requirements on every component have to be considered on a case by case basis. Issues to be considered during the conceptual and detailed design of a component as well as its direct environment are: Expected lifetime of the component and therefore frequency of handling. Expected activation of the component to be handled and its environment. Expected contamination of the component to be handled and its environment. Size and weight of component to be handled. Complexity of geometric arrangement of the component and its environment. Handling areas. In most cases the basic driver is the expected lifetime or end of life mode of the addressed component. Decommissioning

41 Spallation Neutron Source Targets Proton Beam Power LANSCE 100 kw solid target Vertical handling ISIS (RAL) 160 kw solid target Horizontal handling SINQ (PSI) 1000 kw solid target Vertical handling SNS (ORNL) 2000 kw mercury target Horizontal Handling JSNS (JAERI) 1000 kw mercury target Horizontal Handling Full remote Handling is essential Typical Heat loads Mean power density kw/l Peak Power density MW/l (Small when compared to the positron target.)

42 Alternative Concepts (2) - Vertical Services disconnected and target removed to a storage facility. Later can be worked on in a separate remote handling facility

43 Complex Handling Equipment (JSNS)

44 ILC Positron Source WS KURIKI Masao Summary and Overview A framework for the technical decision is decided. Equal opportunity is reserved for all methods. Hybrid of the conventional and undulator is one of the most viable candidate. 20 April