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Linear Collider R&D in the U.S.

Linear Collider R&D in the U.S. Steve Holmes Chicago Linear Collider Workshop January 9, 2002. Outline. Goals R&D Program Elements NLC Activities in the U.S. TESLA Activities in the U.S. Site Studies in the U.S. Remaining Technology Challenges. Goals of the U.S. Program. Context

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Linear Collider R&D in the U.S.

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  1. Linear Collider R&D in the U.S. Steve Holmes Chicago Linear Collider Workshop January 9, 2002

  2. Outline • Goals • R&D Program Elements • NLC Activities in the U.S. • TESLA Activities in the U.S. • Site Studies in the U.S. • Remaining Technology Challenges

  3. Goals of the U.S. Program • Context The directors of the U.S. laboratories have publicly stated their support for construction of a linear collider as an international endeavor based on the optimum technology. This vision has been further supported by the HEPAP Subpanel and its European and Asian counterparts. • Goals The goal of the U.S. Linear Collider R&D program is to develop the technology that would support construction of a linear collider, operating at an initial energy of 500 GeV and luminosity of at least 1034 cm-2 sec-1, and upgradable to an energy in excess of 1 TeV. • Bulk of the U.S. effort is currently being directed into x-band (11 GHz) based implementation. • Aiming for technology demonstration/decision on the timescale of 2003-04. (As is superconducting effort.)

  4. Goals of the U.S. ProgramPerformance Parameters

  5. LC R&D Program Elements • Energy Performance • RF Structures • An accelerating structure must be developed that can support the desired gradient in an operational setting and there must be a cost effective means to fabricate this structure. • RF power generation and delivery • The rf generation and distribution system must be capable of delivering the power required to sustain the design gradient.  Demonstration projects: NLC 8-pack test, TTF-II • Luminosity Performance The specified beam densities must be produced within the injector system, preserved through the linac, and maintained in collision at the interaction region. • Damping ring performance • Vibration specification and site characterizations. • Wakefield suppression/compensation and IR feedback schemes.  R&D Facilities: ATF, ASSET, NLCTA, TTF, and LINX(?)

  6. LC R&D Program Elements • Energy Upgrades There need to be plausible visions of how to upgrade the energy (to and beyond 1 TeV) somewhere down the road.  Gradient R&D to establish the limits of x-band and SC structures. • Site(s) At least one viable site has to be identified and understood. This includes both technical feasibility and public acceptance/support.  Site studies • Cost The cost of facility construction and operation has to be understood.

  7. LC R&D Program ElementsNLC(/JLC) Program SLAC FNAL LBNL LLNL KEK Structures Gradient R&D ✓ ✓ ✓ Industialization ✓ Power Source/Distribution Klystron Development ✓ ✓ Modulator Development ✓✓ ✓ System Integration 8-pack test ✓✓✓ ✓ Civil/Siting ✓ ✓ ✓ Injector Source/linacs ✓ ✓ Damping Rings ✓ ✓ Beam Delivery ✓ ✓

  8. The NLC R&D ProgramStructures/Gradient R&D An aggressive R&D Program has been triggered by observation of cavity deterioration following 1000+ hours of operation a little over a year ago. Test Structure L (m) Vg (% c) Maximum Gradient a Stable Operation b DDS3 1.8 12 50 40 T105VG5 1.0 5 70 60 T53VG5 0.5 5 85 65 T53VG3 0.5 3 90 70 (NLC Spec) • Unloaded gradient (MV/m) used during processing. • Unloaded gradient (MV/m) at which operation is stable. 5000 hours of high-power operation of the NLCTA.

  9. The NLC R&D ProgramStructures/Gradient R&D 1.8 m Vg = 12 % 0.5 m Vg = 5 % 1.0 m Vg = 5 % 0.5 m Vg = 3 % 1500 hrs 1700 hrs 500 hrs 1200 hrs Hours of Operation at 60 Hz

  10. Input 58 Cells Output The NLC R&D ProgramStructures/Gradient R&D T53VG3 (vg from 3.3% to 1.6% c) Distribution of Breakdowns (70 MV/m, 400 ns, 10 hr run) Structure (T53VG3RA) with adaptive input coupler now being tested.  It appears likely that the next iteration NLC design will be based on low group velocity, modest length accelerating structures.

  11. The NLC R&D ProgramStructures/Industrialization The NLC requires ~11,000, 0.9 meter, accelerating structures to reach 500 GeV. Fermilab has undertaken the task of developing an industrialization process for x-band structures fabrication • Short term Goals • Driven by desire to initiate 8-pack test at SLAC in late 2003/early 2004 • Structures fabrication facility • Assembly of eighteen 0.9 (or twenty four 0.6) meter structures • Includes twelve (or 18) destined for 8-pack test at SLAC • Capability of >1 structure/month by December 2002 • Tolerances/acceptance criteria • Develop complete understanding of tolerances and develop QC criteria and specifications • Girders • Develop girder design and prototype • Delivery of two complete girders to SLAC for 8-pack test

  12. The NLC R&D ProgramStructures/Industrialization • Status • IB-4 conversion to structures fabrication facility nearly complete (w/NICADD support) • First 20 cell Fermilab structure, FXA-001, complete • FXA-002 nearing completion “Small” furnace and the structures fabrication facility at Fermilab

  13. The NLC R&D ProgramStructures/Industrialization • Goals for FY02 • Complete fabrication facility • Fabricate and test FXA-002,003 • Fabricate and test FXB-001-003 • Achieve production rate of one structure/month (December 2002) • Complete structures QC and acceptance criteria • Identify vendors and production techniques for FXC-001-006 • Prototype of support girders FXA-001 undergoing bead pull measurement at Fermilab

  14. The NLC R&D ProgramRF Power Sources/Klystrons • The NLC requires ~2000 klystrons, each capable of delivering • 75 MW • 3 msec • 120 Hz • Status • 75XP1 constructed and operated at 75 MW x 3 msec (@10 Hz) • Three more tubes, one built jointly with CPI, are being fabricated to be ready for test in first half of 2002 • Eight tubes required by end of 2003 for 8-pack test. 75XP1 tube at SLAC

  15. The NLC R&D ProgramRF Power Sources/Modulators The NLC requires ~250 modulators each capable of delivering • 500 KV • 3 msec • 120 Hz • Status • Development based on solid state high power switching technology, led by LLNL • 500 KV x 3 msec achieved in “4-Dog” “4-Dog” Solid-State Modulator at SLAC

  16. The NLC R&D Program8-pack Test “8-pack” test: Proof of principle demonstration of the NLC rf generation and distribution system Goals: “Single feed” demonstration in 2002 • Deliver rf power suitable to support 70 MV/m (unloaded) for one girder (5.4 m) of structures. • Test facility for rf power system to run independently of the high-gradient structure testing. Complete 8-pack in late 2003 • Demonstrate full power source with one DLDS arm. • Demonstrate full power operation of two girders (10.4 m) worth of accelerating structures, including at least one of the final RDDS design.

  17. The NLC R&D Program8-pack Test Full “8-Pack” NLCTA Fall 2003 NLC “Single Feed” (5.4 m of Accelerator)

  18. The NLC R&D ProgramOther Areas • Electron polarization with thin strained-lattice (SLAC/Wisconsin/Nagoya) • Polarization of 78% measured at NLC-spec beam density with no sign of charge saturation. • Damping ring studies at the ATF (KEK/SLAC/LBNL). • Intra-beam scattering. • Multi-bunch dynamics. • Permanent magnet R&D (FNAL/LBNL) • Very close to achieving required 1 mm center stability under adjustement • Final focus and beam collimation (SLAC/DESY) • Optics designs and collimator wakefield studies at ASSET • Linx proposal? • Photon-photon collider (LLNL). • IR design and Mercury laser prototype.

  19. The NLC R&D ProgramLINX Proposal Goals: • Test stabilization techniques proposed for future linear colliders and demonstrate nanometer stability of colliding beams • Investigate new optical techniques for control of beam background • Provide a facility where ultra-small and ultra-short beams can be used for a variety of other experiments • Eventually gamma-gamma facility What is it?: A facility to provide e+e- collisions with 30 GeV, ~50nm beams

  20. TESLA R&D in the U.S. The U.S. is in a unique position as the only region in the world in which the technology choice for a linear collider does not appear to be “locked in”.However the character of the U.S. effort on TESLA is fundamentally different from the NLC program because leadership comes from abroad (DESY). • US members of the TESLA collaboration • Argonne National Laboratory • Cornell • Fermilab • Jefferson Lab • UCLA • Elements of the U.S. Program • Collaboration on construction and operation of the TESLA Test Facility (TTF) • Collaboration on preparation of the TESLA proposal • Superconducting materails/processing/fabrication R&D • Injector development and R&D • Engineering/cost study of the TESLA proposal (w/SLAC participation) • SCRF operational experience at Cornell and JLab

  21. TESLA R&D in the U.S.Highlights • Superconducting structure R&D • Fundamental investigations into breakdown phenomona, surface conditions and processing at Cornell • Flat beam studies at Fermilab/NICADD Photoinjector Laboratory (FNPL) • Goal • Generate a flat beam with an emittance ratio tailored to future linear collider requirements (eH/eV 100) • Typical emittance ratio achieved thus far is ~40 (@17 MeV and 1 nC) • Next step is to increase emittance ratio by decreasing space charge.

  22. TESLA R&D in the U.S.Highlights • Engineering/Cost Study • Develop an understanding of: • Scope included in the TESLA estimate • Basis and estimating methodology • Supporting studies (industrialization, schedules, etc.) • Implicit (or explicit) implementation choices • Mapping onto a U.S. style estimate • Report should be available by mid-to-late February • Opportunities • Activities centered at FNPL (many also applicable to NLC): • Flat beam experiments • Remote operations demonstration • 3.9 GHz (3rd harmonic) cavity to support longer bunches • Polarized rf guns? • Layout/proposal for Photoinjector III • Engineering study of TESLA in a deep site • Pursue other opportunities with U.S. collaborators

  23. LC Site InvestigationsU.S. Sites 127

  24. Outstanding Technology Challenges(SDH Perspective) • Energy Performance • RF Structures • It is safe to assume that both NLC and TESLA will demonstrate structures capable of supporting their design accelerating gradients (50 and 24 MV/m respectively) over the next year or so. • The critical issue that is going to take longer is to develop/demonstrate the manufacturing methodology that could allow construction of the linac in a finite time, for a finite cost (especially in the case of NLC/JLC). • RF power generation and delivery • The NLC/JLC rf distribution system has yet to be demonstrated. It is clever, but may not work. The fall back is a system similar to that described in the 1996 ZDR. Alternative implementations deserve continued consideration. • Both NLC and TESLA have to develop/demonstrate an industrial capability for delivering klystrons and modulators. • Multibeam klystron average tube lifetime needs demonstration

  25. Outstanding Technology Challenges(SDH Perspective) • Luminosity Performance: There are so many challenges (and opportunities) here it is impossible to list them all. A sampling: • Sources • Polarization (e- appears OK, what about e+?) • Flat beams • Damping Rings • Damping ring performance specs still await demonstration at ATF • The TESLA damping ring seems somewhat problematic due to issues (like space-charge) related to its large circumference. • Emittance preservation • Tolerances, alignment mechanisms, feedback algorithms all have to be defined in greater detail for both NLC and TESLA. • IR Feedback • Seems to be a viable concept for TESLA, can NLC scheme be validated? • Is LINX necessary or desirable testbed? • Reliability • We need a serious assessment/reliability model for these machines.

  26. Outstanding Technology Challenges(SDH Perspective) • Energy Upgrades • 800-1000 GeV • NLC has a relatively clean vision of achieving 1 TeV based on doubling the length of the linac. • TESLA has a vision of 800 GeV based on an rf power upgrade with a fixed length linac. This assumes a performance of 35 MV/m in the accelerating structures. This has yet been demonstrated, and is unlikely before TTF-II (2003/04) • Beyond 1 TeV? • Possible paths for NLC and TESLA have not been shown. Do they exist? • Site(s) • Criteria definition • Site investigation and characterization • Public/community Relations • (DESY is clearly ahead in this area) • Cost • This has to be iron-clad

  27. Summary Linear Collider R&D is being pursued in the U.S. and abroad with a goal of establishing underlying technologies in late 2003/early 2004 timeframe. Both NLC and TESLA are currently on paths that are expected to lead to credible technology demonstrations on this timescale. • Current support levels in the U.S. (and perhaps also abroad) could imperil this timescale. We need more resources (=people +$) on this. • The experimental community can help by getting directly involved in the machine R&D and technology discussion. If we are successful on the R&D (and establishing public support and forming an international collaboration) the world could construct such a facility over the ~2006-2012 time period

  28. 9th International Workshop on Linear Colliders • February 4-8, 2002 at SLAC • http://www-conf.slac.stanford.edu/lc02/

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