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LC-BEAM-3 ILC Collimator Damage Test

spoiler. LC-BEAM-3 ILC Collimator Damage Test . Nigel Watson (Birmingham) ATF Technical Board, 29-May-2007. Purpose of Proposal ILC Collimator Design R&D Required ATF Proposal. Purpose/Outputs. Understand survival properties of candidate materials for ILC spoilers

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LC-BEAM-3 ILC Collimator Damage Test

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  1. spoiler LC-BEAM-3ILC Collimator Damage Test Nigel Watson (Birmingham) ATF Technical Board, 29-May-2007 • Purpose of Proposal • ILC Collimator Design • R&D Required • ATF Proposal

  2. Purpose/Outputs • Understand survival properties of candidate materials for ILC spoilers • Experimental test necessary to support simulations • Examine beam damage from impact on thin targets (SEM) • Measure surface motion (VISAR) to validate shockwave modelling • In parallel with R&D to optimise for wakefield performance ATF Technical Board / 29-May-2007

  3. ILC Spoiler Design • Design of spoiler jaws (geometry and materials) to optimise performance for wakefields: • E.M. modelling: GdfidL - J.Smith, ECHO - TEMF • T480 beam test of collimator profiles (Fernandez-Hernando, Molloy, NKW + …) • Develop data-validated ability to predict (3D) short range transverse wakes to 10% in regimes ~ ILC • Realistic wakefield models implemented in tracking codes (Bungau, Latina) • “Simple”, direct experimental measurement at ESA • … and beam damage • Fluka, Geant4, EGS simulations (Fernandez-Hernando, Bungau, Keller, NKW) • ANSYS (Ellwood, Greenhalgh – RAL/STFC) • More difficult to quantify “significant” damage • Need to consider wakefield and damage mitigation designs together ATF Technical Board / 29-May-2007

  4. 0.6c0 a Starting point • Long, shallow tapers (~20mrad?), reduce short range transverse wakes • High conductivity surface coatings • Robust material for actual beam spoiling • Long path length for errant beams striking spoilers • Large c0 materials (beryllium…, graphite, ...) • Require spoilers survive at least 2 (1) bunches at 250 (500) GeV • Design approach • Consider range of constructions, study relative resiliance to damage (melting, fracture, stress) • Particularly important for beam-facing surfaces (wakefields) • Also within bulk (structural integrity, heat flow) • Design external geometry for optimal wakefield performance, reduce longitudinal extent of spoiler if possible • Use material of suitable resivity for coating • Design internal structure using in initial damage survey seems most appropriate. ATF Technical Board / 29-May-2007

  5. Spoilers considered include… 0.6c0 2.1010 e-, Ebeam=250 GeV, sxsy=1119mm2 also, Ebeam=500 GeV 2mm 335mrad 10mm Option 1: Ti/C, Ti/Be As per T480 Ti, Cu, Al Graphite regions Option 3: Ti/C Option 2: Ti/C, Cu/C, Al/C 0.6 Xo of metal taper (upstream), 1 mm thick layer of Ti alloy 0.3 Xo of Ti alloy upstream and downstream tapers [Details, see Eurotev Reports 2006-015, -021, -034] ATF Technical Board / 29-May-2007

  6. 2 mm deep from top Full Ti alloy spoiler 810 K 405 K 270 K 135 K ∆Tmax = 870 K per a bunch of 2E10 e- at 500 GeV σx = 79.5 µm, σy= 6.36 µm [L.Fernandez, ASTeC] ATF Technical Board / 29-May-2007

  7. beam Ti C 10 mm deep from top Ti alloy and graphite spoiler Temperature data in the left only valid the Ti-alloy material. Top increase of temp. in the graphite ~200 K. Dash box: graphite region. Peak at the exit 405 K 270 K 200 K 135 K ∆Tmax = 295 K per a bunch of 2E10 e- at 250 GeV σx = 111 µm, σy= 9 µm [L.Fernandez, ASTeC] ATF Technical Board / 29-May-2007

  8. 2 mm deep from top Ti alloy and graphite spoiler Temperature data in the left only valid the Ti-alloy material. Top increase of temp. in the graphite ~400 K. Dash box: graphite region. 540 K 405 K 400 K 270 K ∆Tmax = 575 K per a bunch of 2E10 e- at 500 GeV σx = 79.5 µm, σy= 6.36 µm [L.Fernandez, ASTeC] ATF Technical Board / 29-May-2007

  9. 10 mm deep from top Ti alloy and graphite spoiler Temperature data in the left only valid the Ti-alloy material. Top increase of temp. in the graphite ~400 K. Dash box: graphite region. 540 K 405 K 400 K 270 K ∆Tmax = 580 K per a bunch of 2E10 e- at 500 GeV σx = 79.5 µm, σy= 6.36 µm [L.Fernandez, ASTeC] ATF Technical Board / 29-May-2007

  10. 10 mm depth from top Ti alloy (solid central region) and beryllium spoiler (all tapers) 675 K Temperature data in the left only valid the Ti-alloy material. ∆Tmax = 675 K per a bunch of 2E10 e- at 500 GeV σx = 79.5 µm, σy= 6.36 µm [L.Fernandez, ASTeC] ATF Technical Board / 29-May-2007

  11. Summary of simulations Temperature increase from 1 bunch impact Exceeds fracture temp. Exceeds melting temp. ATF Technical Board / 29-May-2007

  12. Manufacturing study Ti6Al4V profile • Ti “option 3”, spoiler can survive if profile not supported by C (rigidity, uniformity of surface, taper angle) • At 50mrad, 0.6c0(Ti6Al4V) in z is 1mm thick layer • Wire erosion process used, also characterise surface quality • Importance of outer geometry optimisation from wakefield study • Pillars are artefact of ESA vacuum vessel ATF Technical Board / 29-May-2007

  13. beam 2 ILC bunches [Ellwood/RAL] • ANSYS for transient mechanical stress, temperature rise • Peak stress from bunch 1 ~ arrival time of bunch 2 • Time structure important for tests • Realistic spoiler energy depostion from FLUKA • Consistent results from G4/EGS ATF Technical Board / 29-May-2007

  14. 2d shockwave study beam Use “option 3” spoiler with simple heated zone ~ beam dimensions Most damage caused by reflected shear waves Depends on angle of incidence of reflected wave and free surface, i.e. taper angle from wakefield optimisation Reflected Shear Waves Heated Zone Compressive waves Reflected tensile waves ATF Technical Board / 29-May-2007

  15. Code benchmarking • Gives some confidence that our simulations are reasonable • Simulation of existing Cu data encouraging • Need to understand mechanical properties of Ti alloy (or Be) in rapid heating / shock regime • Effect of two bunch impacts • Beam timing required for meaningful tests • Found single bunch/2nd bunch do need delta t ~ILC bunch timing for most useful information • Too low energy at FLASH for full shower development • Considered options at FLASH, ESA,… ATF Technical Board / 29-May-2007

  16. Fluka Benchmark Observed size of beam damage hole in Cu, from FFTB Fluka prediction of beam damage, good agreement with data (NB: evaporated vs. melted – expect data < FLUKA) [Measurements c/o Marc Ross et al., Linac’00] FLUKA SLAC data Measured impact point size /mm2 Simulated impact point size /mm2 Incident e-/mm2 (+/- 2s) Incident e-/mm2 (+/- 2s) x107 ATF Technical Board / 29-May-2007

  17. Summary & New ATF Proposal • Good agreement between FLUKA, GEANT4, EGS4 on energy deposited • Resulting mechanical stresses examined with ANSYS3D • Study beam damage in candidate materials • Experimental tests to reduce largest uncertainties in material properties • Study geometries which can reduce overall length of spoilers while maintaining performance • Means of damage detection, start engineering design of critical components • Revisit collimation requirements for materials (0.6c0 optimised?) • Combine information on geometry, material, construction, to find acceptable baseline design for • Wakefield optimisation • Collimation efficiency • Damage mitigation ATF Technical Board / 29-May-2007

  18. beam X X X X 10mm target area Cu Ti y x ATF Proposal sample holder • Initially, single pulse operation • Locate reference position in sample (low charge) • Beam to damage site #1, … # N (same charge, size) • Change size (charge density), … • End of test: remove sample from vessel, examine with SEM offline • Phase 2: instrumented test of materials dynamics low mass mounting From discussions with Stewart Boogert reference pin hole guide channels pin hole ATF Technical Board / 29-May-2007

  19. Proposed Vessel ATF Technical Board / 29-May-2007

  20. Wire scanner + screens ATF Technical Board / 29-May-2007

  21. Estimated damage region ATF Technical Board / 29-May-2007

  22. Fluences out of beam Integrated +/-5cm in y e.g. 0.6c0 Cu with sxsy =202 mm2 e+e- photons • With details of vessel geometry and regions for radiation protection monitoring, we can estimate effective dose ATF Technical Board / 29-May-2007

  23. Requirements • Alignment/survey • DAQ infrastructure and support • One BPM downstream and one immediately upstream • Polarised positron source vacuum vessel • Request permission to re-use existing hardware • Axis mover to manipulate sample (borrow from LaserWire) • Control software • Additional controllers/stepper motors (UK) • Wire scanner, wires • Gate valves for chamber isolation • Radiation protection – “show stopper” until ATF2? • Provision of local shielding + • Changes to radiation safety document? ATF Technical Board / 29-May-2007

  24. Collaborators • Birmingham: Watson + 1FTE new RA • STFC: Greenhalgh, (0.5FTE) Ellwood, Densham (RAL), (0.5FTE) Fernandez-Hernando + proj. engineering (DL) • SLAC: Keller, McCormick, Seryi • +… ATF Technical Board / 29-May-2007

  25. Summary • Simple first phase test • Compare with existing data • Commission apparatus/operation for study of shockwaves • Exploit ATF’s ILC-like bunch timing • Follow on with test of dynamics of materials with ILC bunch timing, VISAR (RAL experience) • Conduct R&D in parallel with wakefield optimisation of spoilers • Test bench for development of damage detection system • Discussion of request – radiation safety and use of equipment ATF Technical Board / 29-May-2007

  26. Phase 2: dynamics of surface motion ATF Technical Board / 29-May-2007

  27. TTF • ILC bunch spacing • Multiple bunch effects • ~450 MeV • Limited material in transfer line (~0.4c0), space in existing jig (4mm thickness) • Do not get significant shower development in Ti on downstream surface ATF Technical Board / 29-May-2007

  28. ESA • 28.5 GeV • 10Hz, therefore only single pulse damage can be studied • Would need beam focussing to sr~ 10 mm (typical beam size in 2006 sx sy~ 500  100 mm2 • Dispersion in ESA currently limiting ATF Technical Board / 29-May-2007

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