TESLA TeV Collider Project Overview

Transcription

1 Hamburg-Zeuthen Linear Collider Meeting TESLA TeV Collider Project Overview Carlo Pagani Milano & DESY

2 The TESLA Challenge Physical limit is 50 MV/m > 25 MV/m could be obtained Common R&D effort for TESLA Higher conversion efficiency Smaller emittance dilution 1992 TESLA Collaboration set up at DESY Origin of the name Carlo Pagani 2

3 SRF before TESLA From Hasan Padamsee Total >1000 meters > 5 GV Carlo Pagani 3

4 A lot of R&D around the world Understanding Multipactoring A few computer codes developed Spherical shape realized at Genova and qualified at Cornell & Wuppertal Understanding Field Emission Emitters were localized and analyzed Improved treatments and cleanness Cure thermal Breakdown Higher RRR Nb Deeper control for inclusions E acc >5 MV/m 1984/85: First great success A pair of 1.5 GHz cavities developed and tested (in CESR) at Cornell Chosen for CEBAF at TJNAF for a nominal E acc = 5 MV/m Carlo Pagani 4

5 Limiting Problems before 90s Material properties Moderate Nb purity (Niobium from the Tantalum production) Low Residual Resistance Ratio, RRR Low thermal conductivity Normal Conducting inclusions Quench at moderate field Cavity treatments and cleanness Cavity preparation procedure at the R&D stage High Pressure rinsing and clean room assembly not yet introduced Microphonics Mechanical vibrations in low beta structures High RF power required Multipactoring MP has been the major limit for HEPL, and electron linacs to 1984 Pill-box like geometry: higher shunt impedance but higher MP problems Quenches/Thermal breakdown because of low RRR and NC inclusions Field Emission General limit at those time because of poor cleaning procedures and material Carlo Pagani 5

6 The 9-cell TESLA cavity Major Contributors: CERN, Cornell, DESY, Saclay 9-cell, 1.3 GHz, TESLA cavity Figure: Eddy-current scanning system for niobium sheets Figure: Cleanroom handling of niobium cavities TESLA cavity parameters R/Q E peak /E acc B peak /E acc f/ l K Lorentz Ω mt/(mv/m) khz/mm Hz/(MV/m) 2 - Niobium sheets (RRR=300) are scanned by eddy-currents to detect avoid foreign material inclusions like tantalum and iron - Industrial production of full nine-cell cavities: - Deep-drawing of subunits (half-cells, etc. ) from niobium sheets - Chemical preparation for welding, cleanroom preparation - Electron-beam welding according to detailed specification C high temperature heat treatment to stress anneal the Nb and to remove hydrogen from the Nb C high temperature heat treatment with titanium getter layer to increase the thermal conductivity (RRR=500) - Cleanroom handling: - Chemical etching to remove damage layer and titanium getter layer - High pressure water rinsing as final treatment to avoid particle contamination Carlo Pagani 6

7 Preparation of TESLA Cavities Carlo Pagani 7

8 3 rd Cavity Production - BCP 1E+11 1E+10 Q rd Production - BCP Cavities AC55 AC57 AC59 AC61 AC63 AC65 AC67 AC69 AC56 AC58 AC60 AC62 AC64 AC66 AC68 AC79 1E Cavity AC 67 has a cold He leak E acc [MV/m] Carlo Pagani 8

9 Cavity vertical tests and linac performances: <E acc > for Q <E acc > for Q Improved welding Stricter niobium quality control Module performance in the TTF LINAC Carlo Pagani 9

10 TESLA Milestones July International TESLA Cornell University 7-9 August Meeting on SC Cavities and DESY February TESLA Collaboration Board DESY End 1992 Decision to build at DESY the TESLA Test Facility (TTF) March A Proposal to Construct and Test Prototype Superconducting RF Structures for Linear Colliders End 1994 SASE FEL included in TESLA TTF 2 March TESLA Test Facility Linac Design Report-A VUV Free Electron Laser at the TESLA Test Facility at DESY May 1996 first beam at TTF March 2001 TESLA Technical Design Report March 2001 First SASE-FEL Saturation July Positive Conclusions from the German Science Council February 2003 Positive news from German Governement DESY in Hall 3 TTF II TESLA Collider TTF I TESLA X-Ray FEL Carlo Pagani 10

11 What is TESLA now TESLA is at present the combination of: 3 independent Projects: TESLA LC, TESLA X-FEL and TTF2 All based on the outstanding SC linac technology Created by the TESLA Collaboration effort TESLA LC is one of the two remaining competitors for the next HEP large accelerator facility TESLA X-FEL is the core of a proposal for an European Laboratory of Excellence for fundamental and applied research with ultra-bright and coherent X-Ray photons TTF2 will be the first user facility for VUV and soft x-ray coherent light experiments with impressive peak and average brilliance. It will be also the test facility to further implement the TESLA SC Linac technology in view of the construction of large and reliable accelerators Carlo Pagani 11

12 Electropolishing for 35 MV/m EP developed at KEK by K. Saito (origiginally by Siemens) Coordinated R&D effort: DESY, KEK, CERN and Saclay First electro-polished single cell cavities 0.5 mm BCP Surface (1µm roughness) 0.5 mm EP Surface (0.1µm roughness) Electro-polishing (EP) instead of the standard chemical polishing (BCP) eliminates grain boundary steps Field enhancement. Gradients of 40 MV/m at Q values above are now reliably achieved in single cells at KEK, DESY/CERN and TJNAF. Carlo Pagani 12

13 TESLA 800 Performances Vertical Tests 1E+11 1E+10 Q cell 3rd EP Production cavities from - electro-polished 3 rd production Cavities EP by KEK AC72 ep AC73 ep 1400 C heat treatment AC76 ep AC78 ep AC76: just 800 C backing TESLA-800 specs: 35 Q 0 = E E acc [MV/m] Carlo Pagani 13

14 Cavity Vertical Test The naked cavity is immersed in a super-fluid He bath. High power coupler, He vessel and tuner are not installed RF test are performed in CW with a moderate power(< 300W) Carlo Pagani 14

15 TESLA 800 in Chechia Long Term (> 500 h) Horizontal Tests.0E E+10 Q In Chechia the cavity has all its ancillaries Chechia behaves as 1/8 th (1/12 th ) of a TESLA cryomodule Cavity AC73 AC73 - Vertical and Horizontal Test Results Vertical tests of naked cavity Chechia tests of complete cavity CW CW after 20K CHECHIA 10 Hz I CHECHIA 5 Hz CHECHIA 10 Hz II CHECHIA 10 Hz III.0E TESLA-800 specs: 35 Q 0 = E acc [MV/m] Carlo Pagani 15

16 Horizontal tests in Chechia Cavity is fully assembled It includes all the ancillaries: Power Coupler Helium vessel Tuner ( and piezo) RF Power is fed by a Klystron through the main coupler Pulse RF operation using the same pulse shape as TESLA/TTF Carlo Pagani 16

17 EP + Backing played the crucial role DESY EP Infrastructure for 9-cell cavities commissioned with single cell cavities. 9-cell cavities will follow soon. Carlo Pagani 17

18 Piezo-assisted Tuner To compensate for Lorentz force detuning during the 1 ms RF pulse Feed-Forward To conteract mechanical noise, michrophonics Feed-Back Carlo Pagani 18

19 Successful Compensation Cavity detuning induced by Lorentz force during the tests performed in Chechia at TESLA-800 specs Piezo-compensation on Piezo-compensation off Carlo Pagani 19

20 Experience from TTF I operation Maximum cavity operating gradient is set by quench, field emission, or low Q no structure damage is not a hard limit. It results in high cryogenic load, radiation, and dark current does not trip off cavities LLRF can avoid quenches. Action taken prior to the next pulse. Cavity quench detection algorithms and exeption handling procedures analyze the probe signals. Stable Module #1* operation with slowly but steadily increased gradient 1 st quench: Cavity 2 E acc =19 MV/m 2 nd quench: Cavity 6 E acc =21 MV/m 3 rd quench: Cavity 1 E acc =24 MV/m Carlo Pagani 20

21 Performant Cryomodules Three generations of the cryomodule design, with improving simplicity and performances, while decreasing costs Cryomodule Characteristics He gas return pipe 2 K He pipe Input coupler Length # cavities 8 # doublets 1 12 m Static 2 K K 8 K 70 W Beam line Required plug power < 6 kw Sliding 2 K Finger Welded Shields Reliable alignement Strategy Carlo Pagani 21

22 Great experience from TTF I e - beam diagnostics undulator bunch compressor e - beam diagnostics laser driven electron gun photon beam diagnostics preaccelerator superconducting accelerator modules 240 MeV 120 MeV 16 MeV 4 MeV Carlo Pagani 22

23 More experience from TTF II FEL User Facility in the nm Wavelength Range Unique Test Facility to develop X-FEL and LC Six accelerator modules to reach 1 GeV beam energy. Module #6 will be installed later and will contain 8 electro-polished cavities. Engineering with respect to TESLA needs. Klystrons and modulators build in industry. High gradient operation of accelerator modules. Space for module #7 (12 cavity TESLA module). Commissioning RF in June 2003 FEL in 2004 experimental area bypass 1000 MeV 450 MeV 150 MeV BC 3 BC 2 4 MeV 250 m undulators seeding collimator #7 #6 #5 #4 #3 #2 module #1 RF gun Carlo Pagani 23

24 German Government Decisions The decisions of the German Ministry for Education and Research concerning TESLA was published on 5 February 2003: TESLA X-FEL DESY in Hamburg will receive the X-FEL Germany is prepared to carry half of the 673 MEuro investment cost. Discussions on European cooperation will proceed expeditiously, so that in about two years a construction decision can be taken. TESLA Collider Today no German site for the TESLA linear collider will be put forward. This decision is connected to plans to operate this project within a worldwide collaboration DESY will continue its research work on TESLA in the existing international framework, to facilitate German participation in a future global project Carlo Pagani 24

25 Consequences for the LC The path chosen by TESLA to move towards approval was recommended by the German Science Council and is generally considered to be the fastest one. Community will now take the other path used for international projects (e.g. ITER): unite first behind one project with all its aspects, including the technology choice, and then approach all possible governments in parallel in order to trigger the decision process and site selection. ICFA initiative for an international co-ordination: Asian SG US SG European SG Gov Gov Gov ECFA International LC SC Carlo Pagani 25

26 Priorities on Linac Technology In view of the construction of a large scale facility based on TESLA SC Linac Technology, the priorities are: Analyze and Improve Accelerator Reliability, that is: Review TTF Linac components for performances and reliability Review the module design to reduce the assembly criticalities Focalize effort on critical items Give precise specifications for all minor ancillaries Complete the development of the 2 K quadrupole Reach routinely 35 MV/m on cavities. This is due to: Understand and handle all the fabrication process: Make the X-Ray FEL reliable and more performing Allow for higher c.m. Energies of the TESLA Collider Carlo Pagani 26

27 International TRC for LC Greg Lowe Panel Results from International Technical Review (Feb. 2003) Quotes: Ranking 1: R&D needed for feasibility demonstration of the machine Ranking 2: R&D needed to finalize design choices and ensure reliability of the machine Carlo Pagani 27

28 Second to First TRC Comparison Greg Lowe Panels 2003 vs E cm = 500 GeV TESLA TESLA JLC/NLC <JLC/NLC> CLIC CLIC f [GHz] L [cm -2 s -1 ] P beam [MW] P AC [MW] γε y [ 10-8 m] σ y * [nm] Carlo Pagani 28

29 R1 for TESLA Carlo Pagani 29

30 What we planned to do The focus of the work: reach the R1 milestone, as defined in the ITR report (test of one module with beam at 35 MV/m). Due to the extremely tight financial situation at DESY in 2003 this goal will not be reachable within one year. It is therefore very important to approach this goal as much as possible until spring 2004: Test as many 9-cell cavities as possible, with full power for as long as possible at their highest gradient (35 MV/m). Test with a first 9-cell cavity have shown very promising results. In addition it would be very good if at least one 9-cell cavity could be tested with beam (under investigation). In order to prepare the construction of the X-FEL, DESY and its partners will soon focus on issues related to the mass production of all components. This will lead within one to two years to further improvements of the technical design and a better cost evaluation. Carlo Pagani 30

31 US-hosted Linear Collider Options The Accelerator Subcommittee of the US Linear Collider Steering Group (USLCSG) has been charged by the USLCSG Executive Committee with the preparation of options for the siting of an international linear collider in the US. Membership of the USLCSG Accelerator Subcommittee: David Burke (SLAC) Gerry Dugan (Cornell) (Chairman) Dave Finley (Fermilab) Mike Harrison (BNL) Steve Holmes (Fermilab) Jay Marx (LBNL) Hasan Padamsee (Cornell) Tor Raubenheimer (SLAC) Two technology options are to be developed: a warm option, based on the design of the NLC Collaboration, and a cold option, similar to the TESLA design at DESY. Both options will meet the physics design requirements specified by the USLCSG Scope document. Both options will be developed in concert, using, as much as possible, similar approaches in technical design for similar accelerator systems, and a common approach to cost and schedule estimation methodology, and to risk/reliability assessments. Carlo Pagani 31

32 Cold option reference design The major changes to be made to the TESLA design are: An increase in the upgrade energy to 1 TeV (c.m.), with a tunnel of sufficient length to accommodate this in the initial baseline. Use of the same injector beam parameters for the 1 TeV (c.m.) upgrade as for 500 GeV (c.m.) operation The choice of 35 MV/m as the initial main linac design gradient for the 500 GeV (c.m.) machine. The use of a two-tunnel architecture for the linac facilities. An expansion of the spares allocation in the main linac. A re-positioning of the positron source undulator to make use of the 150 GeV electron beam, facilitating operation over a wide range of collision energies from 91 to 500 GeV The adoption of an NLC-style beam delivery system with superconducting final focus quadrupoles, which accommodates both a crossing angle and collision energy variation. At the subsystem and component level, specification changes to facilitate comparison with the warm LC option. Carlo Pagani 32

33 Both with crossing angle Carlo Pagani 33

34 Schedule for task force work Jan. 10: Charge to Accelerator Subcommittee from USLCSG Executive Subcommittee April 14: Joint task force meeting #1 April 16: Status report to USLCSG ExecComm June 15-16: Joint task force meeting #2 July 13: report on work at Cornell ALCW meeting Late August: Final joint task force meeting, to review the final draft of the work, possibly with observers from DESY and CERN invited for comments and suggestions. September : Completion of task force work Carlo Pagani 34

35 And more CERN wants and needs to play a leading role in a Next Linear Collider Discussions in SPC and Council have just started A joint selection of one technology is foreseen in 1 year The 29th of July DOE and NSF will jointly sponsor a one day workshop on RF Superconductivity: to bring DOE and SNF program managers and senior management up to date on the current activities regarding R&D on RF Superconductivity within their sponsored programs The directors of all major possibly interested laboratories (TJNAF, ANL, FNAL, Cornell, ORNL, LANL, NSCL, BNL,..) have been asked to identify their delegation members. Carlo Pagani 35

36 Concluding Remarks The International TESLA Collaboration was created by Bioern Wiik, as DESY Director, to set up the technology and make possible the construction of a high luminosity TeV lepton collider. The technology has been developed and the Linear Collider remains the primary goal for all the TESLA Collaboration founders. Nevertheless The development of the Superconducting linac technology give us a wider responsibility that we should proudly accept as something going beyond the Linear Collider itself. The pursuit of the Linear Collider goal, hopefully based on the TESLA technology, must integrate the new boundary conditions to maximize the probability of having success. Carlo Pagani 36

37 Thanks to TESLA achievements New projects are funded or proposed High Energy Physics TESLA Neutrino Factories and Muon Colliders Kaon Beam Separation at FNAL New TEVATRON Injector Nuclear Physics RIA EURISOL CEBAF Upgrade High Power Proton Linacs for Spallation SNS, Joint-Project, Korea, ESS ADS for Waste Transmutation New Generation Light Sources Recirculating Linacs (Energy Recovery) SASE FELs SNS 200 MHz for Neutrinos Carlo Pagani 37