ERL-Based High-Power EUV-FEL Source (ERL を用いた高出力 EUV-FEL 光源 )

Transcription

1 ERL-Based High-Power EUV-FEL Source (ERL を用いた高出力 EUV-FEL 光源 ) Norio Nakamura High Energy Accelerator Research Organization (KEK)

2 Outline Introduction Energy Recovery Linac(ERL) Design of EUV-FEL Source Simulation Conclusions

3 Energy Recovery Linac (ERL)

4 Energy Recovery Linac(ERL) Ordinary Energy Linear Recovery Accelerator(Linac) (ERL) Merits of ERLs Acceleration energy is almost recovered. Dumped beam power and activation are drastically reduced. High average current (high beam power) can be achieved more easily.

5 Energy Recovery Linac(ERL) Recirculation loop Main SC Linac Injector preaccelerated or decelerated beam accelerated beam Beam dump

6 JLab ERL-FEL ERL FEL at Thomas Jefferson Laboratory(US) First kw-class FEL in the world, average current up to 10 ma IR-FEL: 1.7 µm(1999),14.3 µm (2006) with oscillator UV-FEL: 124 nm (3 rd harminics of 372 nm) with oscillator Parameter IR-FEL UV-FEL Beam Energy MeV 135 MeV Average Current 9.1 ma 5 ma Bunch Charge 135 pc 60 pc Norm. Emittance 8 mm mrad 5 mm mrad Bunch Length 125 fs 100 fs Energy Spread 0.4 % 0.35 % Peak Current 400 A 250 A Bunch Frequency MHz (max.) ERL is suitable for high-power FELs.

7 Compact ERL(cERL) at KEK Demonstration of ERL potentials for future light sources Development of key technologies (photocathode gun, CW SC cavities, ) in operation since 2013 Beam Energy: 20 MeV RF Frequency: 1.3 GHz

8 Recent Progress of cerl (1) High average current & efficient energy recovery 1 ma 10 ma Beam current 0.1 ma Present Δ(P in P ref ) History of achieved beam current Achievement of high beam current (~1 ma ) with efficient energy recovery (~99.97 %) (2) Beam loss reduction (3) Bunch compression COL OUT COL IN 1 THz electron bunch Mitigation of beam halo by collimators at injector Coherent radiation spectrum up to THz by bunch compression in 1 st arc

9 Design of EUV-FEL Source

10 Design Concept Target : 10kW 13.5 nm, 800 MeV Use available technology without too much development Make the most of the cerl designs, technologies and operational experiences

11 Image of EUV-FEL Source 1 st Arc Beam energy: 800 MeV RF frequency: 1.3 GHz Beam Dump 2 nd Arc Gun Merger Injector Linac Rey.Hori/KEK

12 FEL Parameters FEL average power P FEL ρ FEL P electron, P electron = EI av average current Pierce parameter! ρ FEL = # 1 "# 16 I p I A K 2 [JJ] 2 2 λ u γ 3 σ x σ y (2π ) 2 $ & %& 1/3 ( ρ FEL > σ p / p) momentum spread I p = Q b 2πσ t, FEL wavelength λ = λ! u 1+ K 2 $ # & 2γ 2 " 2 % I A =17kA [JJ] = J 0 (ξ) J 1 (ξ), ξ = K 2 / (4 + 2K 2 ) [JJ] =1 Circular-poliarizing undulator σ x = ε nx β x / γ, σ y = ε ny β y / γ K = K y K = 2K x = 2K y Linear-polarizing undulator Linear-polarizing undulator K = eb 0 λ u 2πmc peak current normalized emittance undulator field/period Circular-polarizing undulator High average current, high peak current and low emittance are important. (Lower momentum spread is also required.)

13 Injector & Merger 1 st Arc Beam energy: 800 MeV RF frequency: 1.3 GHz Beam Dump 2 nd Arc Gun Merger Injector Linac Rey.Hori/KEK

14 Injector & Merger Design Vacuum Vessel Segmented ceramic duct 5K Duct 5K Panel 5K Panel 80K Shield 2K He Jacket Electron beam 2K Gas Return Pipe Anode (0V) Ti chamber NEG pump Cathode (-500kV) cerl Injector cryomodule Photocathode DC gun e- Input coupler HOM coupler cavity cells 5K Support 80K Base-plate Input Coupler 2-cell Cavity HOM Coupler Cryomodule design Solenoid magnets Buncher cavity 2-cell SC cavity B : Bending magnets θ=15, ρ=1m Q : Quadrupole magnet injeclon point electron beam Einj~10.5 MeV Injector section (side view) matching section Merger section (top view)

15 Main Linac 1 st Arc Beam energy: 800 MeV RF frequency: 1.3 GHz Beam Dump 2 nd Arc Gun Merger Injector Linac Rey.Hori/KEK

16 Main Linac Design Main linac (9-cell cavities 64 in 16 cryomodules) Cryomodule(4 cavities) 2 Quadrupole triplet cerl cavity Basic unit of main linac structure EUV FEL cavity Quadrupole triplet Under design. A large-aperture pipe will be also applied to the left side. cerl EUV FEL cerl EUV FEL Frequency 1.3 GHz 1.3 GHz Iris diameter 80 mm 70 mm R sh /Q 897 Ω 1007 Ω Q o R s 289 Ω 272 Ω E p /E acc H p /E acc 42.5 Oe/(MV/m) 42.0 Oe/(MV/m) Stable operation at 8.5 MV/m (cerl) 12.5 MV/m (EUV-FEL)

17 Arc Sections & Chicane 1 st Arc Beam energy: 800 MeV RF frequency: 1.3 GHz Beam Dump 2 nd Arc Gun Merger Injector Linac Rey.Hori/KEK

18 Bunch Compression and Decompression Scheme p 2 nd turn p 1 st turn 2 nd turn 1 st turn bunch p t t t RF field t t Beam Dump Injector R 56 < 0, T 566 < 0 1 st Arc + Chicane Main Superconducting Linac EUV Source (ERL) 2 nd Arc R 56 > 0, T 566 > 0 p t Δt = R 56 c " $ # Δp p % ' + T " 566 $ & c # Δp p Undulator(FEL) 2 % ' + & Bunch compressor : 1 st Arc + Chicane Bunch decompressor : 2 nd Arc p t

19 Design of Arc Sections 6.8 m Blue:Bending magnet Red: Quadrupole magnet Yellow:Sextupole magnet TBA: Triple-bend achromat cerl Arc (one TBA cell) cerl arc(photograph) Same configuration with different R 56 signs à Bunch compression & decompression p e m p Bunch compression (1 st arc, R 56 < 0) p t t EUV-FEL Arc (Two TBA cells) with longer magnets for 800-MeV beam Δt = R 56 c Δ p p p t t Bunch decompression (2 nd arc, R 56 > 0)

20 Design of Chicane p L D L B d p t t e- Beam orbit ρ θ Bending magnet Δt = R 56 Δ p c p Four-magnet chicane for bunch compression R 56 = 4L B cosθ 4L 2 BL D ρ 2 cos 3 θ + 4ρθ L B =1m and L D =d=0.51m cerl chicane for path-length control R 56 =-0.15 m ρ=4.1 m, θ=0.246 rad R 56 =-0.30 m ρ=3.0 m, θ=0.340 rad

21 Undulator(FEL) Section 1 st Arc Beam energy: 800 MeV RF frequency: 1.3 GHz Beam Dump 2 nd Arc Gun Merger Injector Linac Rey.Hori/KEK

22 Undulator System for FEL Undulator System(including matching section) Undulator System(FEL) Undulator segment (K=1.652, λ u =28 mm) 18 units QMs for focusing QMs for optics matching. 4.9m 1.12m. Matching Section e - beam Exit of arc or chicane Adjustment of twiss parameter β x,y,α FEL entrance for maximizing FEL output power Circularly-polarizing undulator developed at KEK Parameters of undulator system to be optimized (1)Undulator period and K-value (magnetic gap) (2)Segment length and gap between segments (3)Magnetic strength of QMs for focusing (4)Undulator tapering

23 Simulation

24 Injector & Merger Optimization of Injection beam by simulation Bunch charge: Q b =60pC, Injection energy: E inj =10.5 MeV, Bunch length: σ t ~ 1ps entrance of main linac y[mm] ε nx =0.65 mm mrad ε ny =0.73 mm mrad x[mm] e - p/mc σ t =1.08 ps σ p /p=0.347 % t[ps] 5.0

25 Bunch Compression exit of chicane σ t =55.0 fs σ p /p=0.112 % 5ps Peak current ~600 A entrance of 1 st arc σ t =1.02 ps σ p /p=0.101 % ε nx =2.67 mm mrad ε ny =0.72 mm mrad e - ε nx =0.65 mm mrad ε ny =0.73 mm mrad entrance of main linac σ t =1.08 ps σ p /p=0.347 % ε nx =0.65 mm mrad ε ny =0.73 mm mrad

26 FEL Performance <γβ>= σ t =51.4 fs σ p /p=0.112 % FEL power with 6% tapering: 13.7/ /19.5 ma (P FEL =84 µj x MHz =13.7 kw, I av =60pC x MHz=9.75 ma) e - <γβ>= σ t =53.0 fs σ p /p=0.247 % P FEL > 10 kw is achieved.

27 Bunch Decompression σ t =53.0 fs, σ p /p=0.247 % exit of FEL Bunch decompression is achieved without beam loss. e - exit of main linac σ t =2.42 ps σ p /p=2.06 % 5ps Maximum x-size pipe aperture exit of 2 nd arc σ t =2.11 ps σ p /p=0.242 % σ x =2.86 mm, σ y =0.57 mm

28 Conclusions ERL is a suitable accelerator for high-power FELs. ERL-based EUV-FEL source has been designed with available technologies and its performance has been checked by computer simulation. Generation of FEL power more than 10 kw at 10 ma in the designed EUV-FEL source Successful transportation of electron beams throughout the EUV-FEL source without any beam loss Further design work and R&D will improve the source performance and enhance feasibility of the EUV-FEL source for lithography.

29 EUV-FEL Design Group (KEK) T. Furuya, K. Haga, I. Hanyu, K. Harada, T. Honda, Y. Honda, E. Kako, Y. Kamiya, R. Kato, H. Kawata, Y. Kobayashi, T. Konomi, T. Kubo, S. Michizono, T. Miura, T. Miyajima, H. Nakai, N. Nakamura, T. Obina, K. Oide, H. Sakai, M. Shimada, R. Takai, Y. Tanimoto, K. Tsuchiya, K. Umemori, S. Yamaguchi, M. Yamamoto (QST) R. Hajima (Tohoku Unv.) N. Nishimori The design study has been done under collaboration with a Japanese company.

30 EUV-FEL Light Source Study Group for Industrialization S. Ishihara (Leader) I. Matsuda Utsunomiya Univ. T. Higashiguchi Univ. of Hyogo H. Kinoshita Waseda Univ. M. Washio Osaka Univ. T. Kozawa Industrialization of High Power EUV light source based on and R. Hajima KEK H. Kawata et al. N. Sei

31 Thank you for your attention!

32 Backup Slides

33 Effects of CSR Generation of coherent synchrotron radiation(csr) in bending sections Incoherent synchrotron radiation(isr) N ph N e Electron bunch Coherent synchrotron radiation(csr) 2 N ph N e in Bending magnet CSR field becomes strong for higher bunch charge and shorter bunch length Intensity [a.u.] E=800MeV, ρ=3m 60pC, 1ps 60pC, 50fs 6pC, 1ps 6pC, 50fs Coherent SR 60pC 6pC Incoherent SR Frequency [Hz] Electron bunch Strong CSR field from the back part of bunch affects front part CSR in Bending magnet Degrade of beam quality Reduction of FEL power Arc sections/chicane should be designed so as to suppress CSR effects.

34 EUV/X-ray FELs LCLS SACLA FLASH Euro-XFEL LCLSII EUV-FEL Type of linac Normal conducting Super conducting Operation mode Pulse Long pulse CW Country US Japan Germany Germany US ERL scheme No No No No No Yes Repetition rate ~60 <5000 < M 162.5M Beam energy (MeV) ~ Wavelength(nm) ~ Pulse energy(mj) ~10 ~10 <0.5 ~10 ~1 ~0.1 Average Power (W) ~1 ~1 <0.6 ~100 ~1000 >10000 Beam dump power (W) ~1.5k ~0.5k ~6k ~0.5M ~1M ~0.1M Status Operation 2009 Operation 2011 Operation 2004 Construction 2017 Construction 2020 Planning