TESLA Linear Collider project overview and linac technology

TESLA Linear Collider project overview and linac technology R. Brinkmann, DESY ITRP Meeting, RAL Jan. 28, 2004

500 ( 800) Ge. V e+e- Linear Collider Based on superconducting linac technology

The TESLA Collaboration: 54 Institutes from 12 countries MIT (Jan 2004)

Acknowledgement Many thanks to the colleagues from other LC design groups for critical and competent reviews of TESLA design issues! Collaborative effort (e. g. beam dynamics) during TRC process is a step in the right direction

Cost estimate 500 Ge. V LC, one e+e- IP: 3, 136 M€ (no contingency, year 2000) + ~7000 person years

Why… …technology? Low RF losses in resonators (Q 0 = 1010 , pure Nb at T=2 K) High AC-to-beam efficiency Long pulses/many bunches with low RF peak power Fast intra-train orbit&energy feedback & luminosity stabilisation Low frequency (f=1. 3 GHz), small wakefields f 3 Relaxed alignment tolerances, good beam stability

Accelerating gradient on test stand reached 25 MV/m on average for 1999/2000 cavity production

Higher performance cavities: energy reach 800 Ge. V 1 st step: no add. investment, 2 nd step: add cryo+RF power

Site power: 140 MW Linac: 97 MW Sub-systems: 43 MW RF: 76 MW Cryogenics: 78% 65% 60% 21 MW Beam: 22. 6 MW Injectors Damping rings Water, ventilation, …

Main Linac basic unit: 10 MW klystron 3 prototypes delivered from European industry operated at design spec Ongoing: prototypes from two more vendors 3 modules with 12 cavities each Per main linac: 286 units, incl. 2% reserve for failure handling

The sub-systems… • Considerable complexity • technical and beam dynamics challenges Damping ring e+ source Beam delivery e- sources

Preparation of Cavities

Search for clusters in Nb sheets. Eddy current system. DESY eddy current scanning apparatus for niobium discs. 100% Nb sheets for TTF scanned and sorted out An eddy current scanning system for Nb sheets can be industrially produced now on basis of DESY and BAM development

Fluorescence analysis Example of the Nb sheet eddy current scanning test. Arrow indicates the suspicious spot.

Unloaded Quality Factor Q 0 High Gradient Performance Exciation Curves for Cavities from the 3 rd Production Series TESLA goal The First Three Production Series (without electropolished cavities) TESLA goal 35 TESLA goal 30 TESLA goal Accelerating Gradient ( MV/m ) Approx. 70 cavities were produced in three production series. Gradient and gradient spread improved a lot. Six accelerator modules with 8 cavities each were assembled. Three of them were used in the TTF Linac. Modules 4 and 5 tests started in autumn 2003. <Eacc> [MV/m] 25 The First Six Accelerator Modules 20 15 10 5 0 1 2 3 4 1* Accelerator Module no. 5

TESLA Test Facility Linac (Phase-I until 2003) e- beam diagnostics undulator photon beam diagnostics 240 Me. V bunch compressor superconducting accelerator modules 120 Me. V e- beam diagnostics laser driven electron gun preaccelerator 16 Me. V 4 Me. V

Total accumulated beam time 13, 000 h Mainly at 13… 17 MV/m (FEL) Several weeks of module 3 at max gradient 30 MV/m M 5 Test with RF, Q 0 = 8 109 at 25 MV/m (equal RF power to all cav’s – limitation on acc gradient by cav #8)

Approx. 50% of beam time allocated to FEL operation week 3 / 2002 week 7 / 2002 FEL User Operation Accelerator Studies

Beam operation with module #3 at max. gradient (average of 8 cavities) 22 MV/m

TTF Phase-II (from 2004) experimental area bypass undulators seeding 1000 Me. V 450 Me. V collimator #7 #6 #5 #4 150 Me. V #3 #2 4 Me. V module #1 250 m • VUV/soft X-ray FEL user facility down to 6 nm wavelength • Operational experience with 5 accelerator modules • Beam test of module with high-performance EP cavities (M 6) RF gun

Other Test Facilities • PITZ, DESY-Zeuthen: photocathode RF gun (lowemittance beam, mainly FEL-related R&D), n. c. booster cavity (e+ injector prototype) • A 0, FNAL: photocathode RF-gun, 9 -cell cavity & bunch compressor, diagnostic beam line (lowemittance short bunches, flat beams x>> y, and R&D not related to LC) • RF power input coupler test stand, LAL-Orsay

R&D towards higher energy reach: 1. Superstructure • Increase fill factor by 6% • Reduce # of RF couplers by factor 2 Test of two prototypes Sept/Oct. 2002: • Frequency tuning no problem, field flatness >90% • Beam test with long bunch trains at 15 MV/m, d. E/E ~few 10 -4 • HOM damping better than TESLA specs

2. Improvement of Nb surface quality with electro-polishing (pioneering work done at KEK) BCP EP • Several single cell cavities at g > 40 MV/m • 4 nine-cell cavities at ~35 MV/m, one at 40 MV/m

EP facility at DESY, commissioned 2003

CW test of best 9 -cell EP-treated (at DESY) cavity note: no 1400 C titanisation treatment!

CHECHIA test in pulsed mode (two cavities tested to date, similar results) TESLA 500 – 800 design

Calib. Measurement HERA plant High Power Test of a complete EP nine-cell cavity • • Power/k. W • • Eacc/MV/m • • 1/8 th of a TESLA cryomodule 5 Hz, 500 ms fill, 800 ms flattop 35 +/-1 MV/m with no interruption related to cavity-coupler for more than 1000 hours No field emission upto 35 MV/m, small FE > 35 MV/m Active compensation of Lorentz force detuning operational for more than 500 hours Interruptions due to – cryoplant (HERA shutdown, TTF restart) – RF system (power jumps, problem with old LLRF system +modulator)

Lorentz force detuning at high-g successfully compensated with piezo-tuner

HH/SH Linear Collider site • Most of preparation work for “Planfeststellungsverfahren” (plan approval, legal procedure for construction permission) has been completed • Will not start formal procedure unless decision/approval process more advanced • LC and XFEL sites are decoupled

Seismic measurements: Ellerhoop more quiet than HERA (data taken on a Monday, 0. 00 h – 1. 00 h) HERA tunnel Ellerhoop (barn)

Tunnel layout being reviewed: Optimise usage of the cross section

The European X-ray FEL project • Update to TDR in Oct. 2002: XFEL with separate linac • Estimated cost 684 M€ (year 2000) including personnel • Approval for construction as European project by German Government Feb. 2003, incl. 50% funding • Discussion with European Partners ongoing at government and laboratories levels • European project organisation in 2005 and start of construction 2006

New site: starting from DESY, 3. 3 km towards WNW Seismic measurements