An ERL-Based High-Power Free- Electron Laser for EUV Lithography

Transcription

1 An ERL-Based High-Power Free- Electron Laser for EUV Lithography Norio Nakamura High Energy Accelerator Research Organization(KEK) 2015 EUVL Workshop, Maui, Hawaii, USA, June 15-19, 2015.

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

3 Outline Introduction Injector Design Main Linac Design Bunch Compression & Decompression Scheme Design of Arc & Chicane Bunch Compression Simulation FEL Performance Summary and Outlook

4 Motivation 10-kW class EUV sources are required in the future for lithography The order of EUV-FEL size and cost can be acceptable ERL-FELs have merits of energy recovery, low dumped beam power and activation

5 Design Concept Target : 10kW 13.5 nm, 800 MeV Use available technology without too much development Make the most of the designs, technologies and experiences of the Compact ERL(cERL) at KEK

6 Compact ERL at KEK Beam Energy: 20 MeV Max. Beam Current: 80 µa ( à 10 ma ) RF Frequency: 1.3 GHz in operation since 2013

7 Injector Design DC Photocathode gun with the same structure of 2 nd gun at cerl Two cerl cryomodules with six 2-cell SC cavities for E inj =10.5 MeV Two solenoid magnets and one buncher cavity New merger (under design) 500 kv Gun Two solenoid magnets Buncher Two injector cryomodule (Max. E acc : 8 MV/m) Beam E inj =10.5 MeV Injector system of EUV source (merger not included)

8 Injector Parameters Normalized emittance [mm mrad] Optimization of injector parameters before merger 1ps Q b =60 pc E= MeV 2ps Bunch length[mm] Bunch length[mm] Tracking by GPT 60pC/bunch 1 ps : 0.30 mm mrad, 0.25 % à ε n = 0.60 mm mrad, σ p /p = 0.25 merger exit 2 ps : 0.25 mm mrad, 0.25 % à ε n = 0.55 mm mrad, σ p /p = 0.25 merger exit 100pC/bunch 1 ps : 0.57 mm mrad, 0.35 % à ε n = 0.80 mm mrad, σ p /p = 0.35 merger exit 2 ps : 0.35 mm mrad, 0.16 % à ε n = 0.60 mm mrad, σ p /p = 0.16 merger exit Momentum spread[%] 1ps Q b =60 pc E= MeV The results are used as ini8al values for simula8ons including bunch compression ps

9 Design of Main Linac Cavity ERL-EUV cavity (Model 1) TESLA-type 9-cell cavity + 108ϕ beam pipe Under design. A large-aperture beam pipe will be also applied to the left side. cerl cavity (Model 2) stably operated at ~8.5 MV/m Parameters for acceleration mode Model 2 Model 1 Model 2 Model 1 Frequency 1300 MHz 1300 MHz 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 12.5 MV/m seems achievable due to reduced E p /E acc.

10 Main Linac Optics Main linac optics 2 cryomodules Quadrupole triplet n Main Linac 64 cavities in 16 cryomodules (4 cavities/cryomodule) E acc 12.5 MV/m n Optics Focusing of quadrupole triplet at every two cryomodules Body/edge focusing of cavities Betatron function optimization against BBU à I th,bbu > 190 ma Symmetric for acceleration and deceleration

11 HOM Heating Non-resonant heating Parasitic loss absorbed at HOM damper P loss = k loss Q b 2 f b k loss : Loss factor, Q b : bunch charge f b : bunch frequency Estimation of loss factor k loss ~ 20 1 ps ~ 15 2 ps Examples of parasitic loss power Bunch 9.75mA x 2 60pC 162.5MHz 8mA x 2 100pC 81.25MHz 1 ps 23.4 W 32 W 2 ps 17.6 W 24 W Max. absorption power of HOM damper : 30 W (first target), 100 W (final goal) Heating resonant to monopole HOMs Difference between monopole HOM frequency and harmonics of bunch frequency momopole f HOM [MHz] Bunch frequency f b [MHz] : frequency difference within 10 MHz Max. absorption power of the HOM damper restricts the bunch charge, length and frequency. The bunch frequency should be selected so as to avoid the resonant heating.

12 FEL Parameters FEL power at saturation P sat ρ FEL P electron, Pierce parameter! ρ FEL = # 1 "# 16 I p = I p I A Q b 2πσ t, λ = λ! u 1+ K 2 $ # & 2γ 2 " 2 % K 2 [JJ] 2 2 λ u γ 3 σ x σ y (2π ) 2 I A =17kA P electron = EI av [JJ] = J 0 (ξ) J 1 (ξ), ξ = K 2 / (4 + 2K 2 ) [JJ] =1 $ & %& Helical undulator 1/3 σ x = γε nx β x, σ y = γε ny β y Planar undulator Photon wavelength and undulator parameters K = K y K = 2K x = 2K y Planar undulator Helical undulator High peak current and low emittance are important for FEL power.

13 Bunch compression and decompression scheme (1) 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 1 st Arc R 56 > 0, T 566 > 0 (R 56 < 0, T 566 < 0 ) Main Superconducting Linac EUV Source (ERL) 2 nd Arc R 56 < 0, T 566 < 0 (R 56 > 0, T 566 > 0 ) p Undulator(FEL) p FEL light t Bunch compressor : 1 st Arc Bunch decompressor : 2 nd Arc t

14 Bunch compression and decompression scheme (2) 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 Undulator(FEL) Bunch compressor : Chicane : 1 st Arc + Chicane Bunch decompressor : 2 nd Arc p FEL light t

15 Design of Arc Sections (1) Dispersion function[m] Betatron function[m] cell TBA lattice and optics(r 56 =0.0 m) ρ =3 m, θ =π/8 rad, L B =1.178 m, L Q =0.4 m, L SX =0.2 m η c TBA cell R 56 = 4ρ(θ sinθ)+ 2η c sinθ SX3 SX4 SX1 SX2 TBA cell B Q Q Q B B Q Q Q B Q Q Q Q B Q Q Q B B Q Q Q B 0 SX1 SX SX3 SX4 30 s[m] B: Bending magnet, Q: Quadrupole magnet, SX: Sextupole magnet Eight sextupole magnets can be inserted in the arc to optimize T 566.

16 Design of Arc Sections (2) Dispersion func8on[m] Betatron func8on[m] Dispersion func8on[m] Betatron func8on[m] R 56 =0.3m Examples of 2-cell TBA optics with different R s[m] R 56 =0.6m s[m] Dispersion func8on[m] Betatron func8on[m] Dispersion func8on[m] Betatron func8on[m] R 56 =-0.3m s[m] R 56 =-0.6m s[m] The 2-cell TBA lattice has a wide dynamic range of R 56. Momentum acceptance is more than 4% for horizontal half-aperture of ~5cm.

17 Design of Chicane L D Four-magnet chicane d L B R 56 = 4L B cosθ 4L 2 BL D ρ 2 cos 3 θ + 4ρθ Beam orbit Bending magnet ρ θ Chicane optics for L B =1m and L D =d=0.51m R 56 = m, ρ=3 m, θ=0.34 rad R 56 = m, ρ=4.1 m, θ=0.246 rad

18 Bunch Compression by Arc Main Linac + 1 st Arc (R 56 =0.30 m) simulation by Elegant Q b =60 pc E=10.5 MeV Main linac E=800 MeV M1 1 st arc entrance of main linac σ t =1.00 ps σ p /p=0.250 % entrance of 1 st arc σ t =1.01 ps σ p /p=0.099 % exit of 1 st arc σ t =43.9 fs σ p /p=0.107 % ε nx =0.60 mm mrad ε ny =0.60 mm mrad ε nx =0.60 mm mrad ε ny =0.60 mm mrad ε nx =2.27 mm mrad ε ny =0.60 mm mrad RF phase and sextupole strengths maximizing the Pierce parameter K 2 (SX1)=-54.6 [m -3 ], K 2 (SX4) =26.4 [m -3 ], φ RF =96.7 [deg]

19 Bunch Compression by Chicane Main Linac + 1 st Arc (R 56 =0.0 m) + Chicane (R 56 =-0.3 m) Q b =60 pc E=10.5 MeV E=800 MeV Main linac M1 1 st arc M2 Chicane entrance of main linac σ t =1.00 ps σ p /p=0.250 % entrance of 1 st arc σ t =0.997 ps σ p /p=0.104 % exit of chicane σ t =43.8 fs σ p /p=0.110 % ε nx =0.60 mm mrad ε ny =0.60 mm mrad ε nx =0.60 mm mrad ε ny =0.60 mm mrad ε nx =1.72 mm mrad ε ny =0.60 mm mrad RF phase and sextupole strengths maximizing the Pierce parameter K 2 (SX1)=-91.2 [m -3 ], K 2 (SX4) =23.6 [m -3 ], φ RF =82.4 [deg]

20 Bunch Compression by Arc & Chicane Main Linac + 1 st Arc (R 56 =-0.15 m) + Chicane (R 56 =-0.15 m) Q b =60 pc E=10.5 MeV E=800 MeV Main linac M1 1 st arc M2 Chicane entrance of main linac σ t =1.00 ps σ p /p=0.250 % entrance of 1 st arc σ t =0.997 ps σ p /p=0.104 % exit of Chicane σ t =43.2 fs σ p /p=0.108 % ε nx =0.60 mm mrad ε ny =0.60 mm mrad ε nx =0.60 mm mrad ε ny =0.60 mm mrad ε nx =1.67 mm mrad ε ny =0.60 mm mrad RF phase and sextupole strengths maximizing the Pierce parameter K 2 (SX1)= [m -3 ], K 2 (SX4) =41.4 [m -3 ], φ RF =82.4 [deg]

21 Peak Current & Slice Emittance Bunch Compression by Arc Bunch Compression by Chicane Q b =60 pc Bunch Compression by Arc + Chicane projected normalized horizontal emittance Slice emittance at high peak currents is lower than the projected emittance.

22 FEL Performance Electron beam parameters: E=800 MeV, Q b =60 pc, f b =162.5/325 MHz Helical undulator parameters: K=1.652, λ u =28 mm, L u =2.8m Bunch compression scheme: 1 st Arc + Chicane 67.6 µj 55.5 µj FEL power without tapering: 9.0/ /19.5 ma FEL power with 10% tapering: 11.0/ /19.5 ma

23 Image of ERL-EUV Design 1 st Arc Beam Dump 2 nd Arc Gun Merger Injector Linac

24 Summary & Outlook Design of ERL-EUV Injector (gun, SRF cryomodule, tracking) Main linac (cavity, optics, HOM BBU and heating) Arcs and chicane (lattice, optics) Bunch compression simulation Performance of the designed ERL-EUV 9 kw power at 9.75 ma without tapering 11 kw at 9.75 ma with tapering Further design work and optimization Improvement of FEL power (tapering, optics, beam&undulator parameters etc.) Bunch decompression simulation à S2E simulation

25 Thank you for your attention!

26 Appendix

27 HOM BBU HOM-BBU threshold current is calculated by Simulation code bi. HOM parameters of Model 1 cavity Calculation of BBU threshold current 0.45 Average threshold <I th > / A HOM randomization effects Frequency randomization std. f / MHz BBU Current / A Δψ (πrad) ΔT/T 0 Scan over the betatron phase advance (0-2π) and return loop length (in one period of the base mode). Minimum BBU current is found to be about 195 ma. (478mA maximum). Considering a Gaussian frequency distribution between linac cavities, the average BBU threshold current grows with the frequency spread σ f increases, reaching about 1.1A when σ f =2MHz. BBU threshold current is well above the expected average current

28 Bunch Compression and Decompression at cerl after deceleration before acceleration σ t =1.34[ps], σ p /p= σ t =1.20[ps], σ p /p= σ t =1.02[ps], σ p /p=0.001 σ t =0.86[ps], σ p /p= K 2 (SXIF2)= [m -3 ] K 2 (SXIF4)= [m -3 ] φ RF (ACC)=24.62 [deg] 3 σ t =0.51[ps], σ p /p= Initial Condition at 1 : Bunch charge : 7.7 pc Initial bunch length : 1 ps Initial momentum spread : 0.1 % Initial norm. emittance : 1 mm mrad K 2 (SXIR2)= [m -3 ] K 2 (SXIR4)= [m -3 ] φ RF (DEC)= [deg] 4 σ t =45.2[fs], σ p /p= Bunch compression and decompression are successfully simulated at cerl.

29 Compensation of CSR effects (1) Q b =60 pc Minimization of CSR-induced horizontal emittance growth x Phase ellipse angle vs beam/fel parameters at chicane exit (bunch compression by chicane) φ CSR =63.4 x φ CSR =63.4 φ phase =32.9 x x φ phase =148.6 x φ CSR =63.4 x φ phase =56.1 1/ρ FEL 2 tan(θ / 2) tanφ CSR = ρ(1 cosθ) (rectangular magnet) tan2φ phase = 2α x γ x β x The phase ellipse and CSR kick directions can be matched at chicane exit. Such optics adjustment is difficult for bunch compression by arc.

30 Compensation of CSR effects (2) Q b =60 pc Minimization of CSR-induced horizontal emittance growth Phase ellipse angle vs beam/fel parameters at chicane exit (bunch compression by arc & chicane) x φ CSR =63.4 φ phase =36.9 x x φ CSR =63.4 x φ phase =151.0 x φ CSR =63.4 x φ phase =63.6 1/ρ FEL 2 tan(θ / 2) tanφ CSR = ρ(1 cosθ) (rectangular magnet) tan2φ phase = 2α x γ x β x The phase ellipse and CSR kick directions can be matched at chicane exit. Such optics adjustment is difficult for bunch compression by arc.