Integrating International collaborations on RD of Xband RF

Integrating International collaborations on R&D of X-band RF technology Zhentang Zhao Shanghai Institute of Applied Physics, CAS July 11，2015

Outline • International collaboration Impacts • The state of art on X-band RF collaboration for LC and FEL • Main infrastructures on X-band RF technology R&D • New strong interests on X-band technology. • Wide and deep collaboration for promoting X-band RF technology • Conclusion

International collaboration impacts • Integrate and unify the global efforts to make breakthrough in short time and cost-effective way. • Make good utilization of various resources from collaborators, including funds, infrastructure, manpower and experience and focus on the cornel challenges, reduce the simple repetition. • . Make the key R&Ds from in series to in parallel • International world infrastructures can integrate collaborations

CLIC collaboration including X-band RF technology Courtesy of Wuensch Walter

The Xb. FEL Collaboration The aim of the Xb. FEL Collaboration is to promote the use of X-band technology for FEL based photon sources. http: //xbandfel. web. cern. ch/ ST Elettra - Sincrotrone Trieste, Italy. CERN Geneva, Switzerland. JU Jagiellonian University, Krakow, Poland. STFC Daresbury Laboratory Cockcroft Institute, Daresbury, UK SINAP Shangai Institute of Applied Physics, Shanghai, China. VDL ETG T&D B. V. , Eindhoven, Netherlands. OSLO University of Oslo, Norway. IASA National Technical University of Athens, Greece. UU Uppsala University, Uppsala, Sweden. ASLS Australian Synchrotron, Clayton, Australia. UA-IAT Institute of Accelerator Technologies, Ankara, Turkey. ULANC Lancaster University, Lancaster, UK.

R&D activities on X-band technology • SLAC, CERN and KEK has kept collaboration on X-band technology for more than 30 years, and carried out many crucial techniques for linear collider (LC), in particular 100 MV/m for accelerating gradient, and NLCTA for beam test. • Compact XFEL could be new breakthrough of X-band application based on present level of X-band technology R&D, so that many FEL labs such as Elettra - Sincrotrone Trieste, SINAP, Ankara University, Australian Synchrotron, STFC, Oslo University and so on, are strongly interested at developing specific X-band technology for compact XFEL. • X-band technology is also available for replacing old accelerators to upgrade beam energy, as Tsinghua University is going to use X-band linac to upgrade the Compton scattering facility. • CPI, Toshiba and CETC force on X-band klystron development, and VDL is good at price X-band RF structure machining.

X-band basis at SLAC - many types of X-band tubes One of four T-type Structures -T 53 VG 3, 60 -Cell 2π/3 Mode TW SW 20 PIL 15 -Cell π Mode SW One of more than 10 High Phase Advance 5π/6 Mode TW Structures, H 60 VG 3 S 18 with HOM Slots and Manifolds. Courtesy of Juwen Wang

X-band basis at SLAC – XTA of NLCTA 1. There were two T 105 accelerator structures working at XTA. 2. 1 st structure was made in 2001, and still running more than 70 MV/m routinely. 3. 2 nd structure was made in 2013, and running as high as 80 MV/m stably. Courtesy of Juwen Wang

X-band basis at SLAC – ASTA Accelerator Structure Test Area (ASTA) The facility includes: 1. Two X-band 50 MW klystrons that can be combined. 2. A variable length pulse compressor that can produce up to 500 MW. 3. The most agile RF system suitable for fast turn around of experiments. 4. One 40 MW S-band klystron 5. IR and UV short pulse lasers Programs intended for this facility: 1. Scan the material for RF accelerator structures using the single cell accelerator structure technology as vehicle for these studies. 2. Test Dielectric Accelerator structures in collaboration with ANL 3. Test highly damped RF structures in collaboration with CERN and KEK 4. Test superconducting materials and structures 5. Photo cathode RF gun development

X-band at CERN for CLIC: X-box 1, X-box 2, X-box 3 1. X-box 1, X-box 2 are running for high power test, beam test. 2. X-box 3 is in the progress of construction, and will be ready soon. 3. Three X-band klystron-based tests stands will be operated through at least 2018. X-box 1 50 MW klystron Inside X-box 1 X-box 2 50 MW klystron Inside X-box 2 X-box 3 Four 7 MW klystrons Courtesy of Weunsch Walter

X-band at CERN: CLIC accelerating structure Operating frequency 12 GHz Accelerating gradient 100 MV/m Peak surface electric field 250 MV/m Pulse length 200 ns Repetition rate 50 Hz Input power 50 MW Breakdown rate <10 -7 BD/pulse/m 1. Many types of structures. 2. 120 MV/m maximum 3. Several structures reached the target of CLIC breakdown rate. Courtesy of Weunsch Walter

X-band at KEK: Nextef and KT 1 1. Tsinghua-made T 24 has been tested in shield-A 2. SINAP-made 1 m-structure will be tested here at shield -A. Nextef X-band B KT-1 X-band A Shield-A Courtesy of Higo Toshiyasu

X-band at KEK: accelerating structures 20 cm structure 60 cm structure In 2003 KX 03 in 2005 Courtesy of Higo Toshiyasu

X-band development results based on LC collaboration • SLAC, CERN and KEK have developed X-band technology remarkably based on international collaboration, and in particular built many high power test setup for X-band high gradient research, and reached 100 MV/m with stable breakdown rate. • SLAC, CERN and KEK also have collaborated with many companies, such as VDL, Toshiba and so on, to develop high quality machining for X-band accelerating structures, and totally hundred of structures have been made, so that a great deal of RF design and fabrication are accumulated. • Klystron is crucial component for X-band technology, and so far two specific types of Xband klystron have also been developed by SLAC, KEK, CERN, CPI and Toshiba collaboration, so that 50 MW and 7 MW X-band klystrons are available for X-band facilities. • Further research on X-band technology will still be based on collaborations.

New strong interests on X-band technology Ø The demand for new FEL facilities is worldwide continuously increasing, spurring plans for new dedicated machines. This led to a general reconsideration of costs and space issues, particularly for the hard X-ray sources, driven by long and expensive multi-Ge. V NC linacs. Ø For these machines the use of X-band technology can greatly reduce cost and capital investment, reducing the linac length and the size of buildings, opening the way to the construction of a multitude of affordable “Regional Facilities”. Courtesy of G. D’Auria

Interests for X-band FELs Ø FERMI FEL Elettra – Sincrotrone Trieste • Linac energy increase → FEL shorter wavelenghts (≤ 1 nm) • Possibility to operate with two linacs at the same time (two e-beam pulses at different energies) Ø Ankara University (Turkish X-ray FEL) • 6. 0 Ge. V linac → FEL wavelengths 0. 1 -10 nm • Possibility to operate at high rep rate (up to 500 Hz) Ø Australian Synchrotron (AXXS–Australian X-band X-ray Source) • Plans for a 6. 0 Ge. V linac Ø SINAP Shangai • Proposal for hard X-FEL (6. 5 Ge. V) submitted to Chinese government. Ø STFC • CLARA FEL Test Facility (Ultra short pulse generation). An S-band linac module (Linac 4) will be replaced with an X-band module as test bed for this technology on FELs. Ø Oslo University • The possibility for a compact FEL based on X-band technology has been presented to the Norwegian light source user community. Several scientists have shown interest for a National Facility. Courtesy of G. D’Auria

FERMI perspectives 1. 5 Ge. V l 4 -80 nm 2 3. 5 Ge. V l < 1 nm 1 S-band linac two e-bunches/RF pulse HF bunch separator Two separate linacs at 50 Hz S-band → 1. 5 Ge. V X-band → 3. 5 Ge. V Courtesy of G. D’Auria

Turkish X-ray FEL (Ankara University) • It consist of: ■ RF photocathode gun ■ Injector ■ Two main linacs S band structure delivering beam @7 Me. V with 250 p. C charge, 2. 5 ps (800μm) lengt and 0. 25 mm rad emittance S-band structures and one X-band structure as linearizer, accelerating beam up to 300 Me. V Two X-band modules: stage one 0. 3 Ge. V 2. 0 Ge. V stage two 2. 0 Ge. V 6. 0 Ge. V ■ Two bunch compressors , Beam delivery lines , Undulator(s), Laser transport line(s) • The advantage of using X-band: – Compact reduction of length with high gradient – Costs reduction – Possibility to go to a high repetition rate (up to k. Hz regime) Courtesy of A. Aksoy 18

Shanghai Photon Science Center at SINAP SXFEL: Shanghai Soft X-ray FEL S-band, C-band, X-band Energy: 0. 84 Ge. V (Phase I), 1. 3 Ge. V (Phase II) Compact hard X-ray FEL (X-band, S-band) Energy: 6. 5 Ge. V, 8 Ge. V (200 m linac) SSRF: Shanghai Synchrotron Radiation Facility Total length: About 550 meters Energy: 3. 5 Ge. V, user operation

SXFEL Project at SINAP Phase I: 8 C-band acc for 4 units PC gun S-band acc X-band acc Upgrade: X-band accelerating structure Parameters Phase I Upgrade Unit 9 3 nm Bunch charge 0. 5~1 n. C Energy 0. 84 1. 2~1. 3 Ge. V 0. 1~0. 15% Energy spread (sliced) 0. 02% 0. 03% Normalized emittance 2. 0~2. 5 mm. mrad Pulse length (FWHM) 1. 1 ps Peak current ~0. 5 k. A Rep. rate 1~10 Hz Output Wavelength Energy spread

X-band plan for compact hard X-ray FEL (On proposal) E=330 Me. V I=300 A, σz=78μm ① ① ③ ② ② ④ E=1900 Me. V I=3000 A, σz=7μm 130 meters X-band linac E=6. 5 Ge. V, I=3 k. A σz=7μm, σδ=0. 021% ⑤ ④ ③ X-band: Phase I: 6. 5 Ge. V@65 MV/m Upgrade: 8 Ge. V@80 MV/m ⑤ Parameters Value Output Wavelength 0. 07 nm Bunch charge 250 p. C Energy 6. 5 Ge. V Normalized emittance 0. 4μm Energy spread (projected) 0. 02% Pulse length (Full) 40 fs Peak current 3 k. A Rep. rate 60 Hz Peak power 10 GW Peak brightness 2*1033

X-band Accelerator Test Facility plan based on collaborations at SINAP 1. SDUV-FEL is one facility about 50 meters long. 2. Most components will be moved to SXFEL. 3. The tunnel will be left for future X-band technology R&D at SINAP.

X-band accelerating structure design by SINAP and CERN Frequency 11424 MHz Phase advance 4π/5 Cell No. 89+2 Effective length 944. 73 mm Cell length, d 10. 497 mm Iris thickness, 2 a 1. 5 mm Ratio of elliptic radius, b_a 1. 8 Aperture, a_r 4. 3~3. 05. mm Group velocity, Vg/c 3. 45%~1. 12% Shunt impedance, R 86. 7~108. 7 MΩ/m Attenuation factor, τ 0. 61 Filling time, tf 150 ns Sc 4. 14~2. 33 MW/mm^2 Emax/E 0 2. 68~2. 02 Hmax/E 0 2. 68~2. 39 m. A/V Input power, Pin 52 MW @65 MV/m 80 MW @80 MV/m Two-Klystrons units 34 @65 MV/m 51 @80 MV/m Coupler design and matching status

X-band plans based on collaborations at SINAP 2014 -2015: start of X-band technology 1 ST 20 -cells X-band deflector 1. RF design at SINAP 2. Fabrication accumulation at SINAP 3. Tuning at SINAP 2015 -2016: 1 st X-band accelerating structure 1. Optimized for XFEL 2. Design based on beam simulation 3. 80 MV/m maximum gradient 2016 -2017: 1 ST T 24 structure for CLIC collaboration. 2016 -2018: 4 one-meter X-band accelerating structure for Xb. FEL Collaboration. 2018 -2019: Stable X-band RF technology for Hard X-ray FEL at SINAP

Wide and deep collaborations on X-band technology • Fruitful results have been carried out based on international LC collaboration, such as NLC and CLIC, and recently it’s still long time and many challenges for LC R&D. • XFEL based on X-band technology is one excellent opportunity for big collaboration between FEL and LC, so that X-band technology can make XFEL facility compact, and more importantly it can be first used for scale facility, and also some crucial techniques can be tested, and then feed back to LC development. • Meanwhile many other linac facilities are also interested at X-band technology, based on upgrading or replacing. • Based on strong interests on X-band technology, wide and deep collaborations on X -band technology should extended, so that more and more infrastructures could be forced on this technology, and make new breakthrough with high efficiency as soon as possible.

Conclusion • Collaborations on high gradient X-band RF technology have been kept for about 30 years, and developed deeply and systematically for electron linear collider in the range of Te. V, in particular NLC and CLIC project. • Recently high gradient X-band RF technology is approaching the target step by step, and there are many crucial techniques, in particular high gradient accelerating structure, to been or being mature. • Compact FEL in the range of ten Ge. V, may be the breakthrough of X-band technology application, moreover many mature techniques could be also used for industry applications, so that wider and deeper collaboration should promote R&D of X-band RF technology.

Thank you for your attention!