SCSS Prototype Accelerator -- Its outline and achieved beam performance --

Transcription

1 SCSS Prototype Accelerator -- Its outline and achieved beam performance -- Hitoshi TANAKA RIKEN, XFEL Project Office 1

2 Content 1. Light Quality; SPring-8 v.s. XFEL 2. What are the critical issues? 3. Mission of the Prototype Accelerator 4. Unique Features of the Prototype 5. Achieved Beam Performance 6. Towards 8-GeV XFEL 2

3 1. SPring-8 v.s. XFEL (1/3) (1) (Peak) Brilliance of ~10 20 (10 24 ) photons/s/mm 2 /mrad 2 /0.1b.w./100A(5A) (2) 1D Spatial Coherence at the sample (3) Pulse Width of ~40psec (4) High Pulse Rate >200KHz Signal Integration Time-Averaged Steady State 3

4 1. SPring-8 v.s. XFEL (2/3) (1) (Peak) Brilliance of ~10 21 (10 32 ) photons/s/mm 2 /mrad 2 /0.1b.w. (2) 2D Full Spatial Coherence at the sample (3) Pulse Width of ~100fsec (4) Low Pulse Rate, 60Hz Shot-by-Shot Time-Sliced Observation Unsteady State 4

5 1. SPring-8 v.s. XFEL (3/3) XFEL provides users with: (1) Transversally full coherent, (2) short pulsed, (3)ultra-intense probe and exciter in x- ray wavelength regime. 5

6 2. What are the critical issues? FEL Interaction Image Undulator Field (1/3) E x v e EM Field by Radiation Electron Orbit z E x v e v e E x 6

7 2. What are the critical issues? (2/3) S N S N S N S N S λ=1å N S N S N S N S N The density modulation of λ-scale is necessary for achieving the amplified undulator radiation. 7

8 2. What are the critical issues? (3/3) (1) Generation of high quality electron beam with small emittance and high peak current (2) Ultimate stability of electron beam (3) Precise overlap of electron beam and undulator radiation (4) Measurement of slice emittance, etc 8

9 3. Missions of the Prototype (1/2) SPring-8 Compact SASE Source (SCSS) adopts three unique systems; a low emittance injector with 500 kv pulsed electron gun, C-band accelerator, and invacuum undulator. The prototype is a test-bench to confirm the performance of each system. 9

10 3. Missions of the Prototype (2/2) The biggest question is whether "emittance conservation" through the injector is a sufficient level or not under the practical error condition. Only the experimental results can answer the above and verify the validity of the injector system. 10

11 Unique Features (1/7) Schematic View 11

12 Unique Features (2/7) Picture from the E-gun 12

13 4. Unique Features (3/7) 4.1. Specially Designed In-vacuum Undulator 45-deg. Tilted Magnet Configuration Period: 15mm Length: 4.5m Period No. : 300 Material: NdFeB Min.Gap: 2mm K-value: 1.8@MinG 13

14 4. Unique Features (4/7) 4.2. C-band Accelerator System initially developed for JLC was used. f RF : 5.7GHz Gradient: 32MV/m RF Power: 53MW Accel. Unit Length: 1.8m RF Pules Width: 2.5µsec 14

15 4. Unique Features (5/7) Schematic View of C-band Accelerator System 15

16 4. Unique Features (6/7) 4.3. Low Emittance Injector with 500kV pulsed E- gun World Standard: Photo-cathode RF-gun based system Most of accelerator physicists at the inside and outside of SPring-8 were negative against the SCSS injector system. 16

17 4. Unique Features (7/7) Beam Energy Peak Current Pulse Width (FWHM) Repetition Rate Cathode Diameter Cathode Temperature Cathode Material Theoretical Thermal Emittance (rms) Measured Normalized Emittance (rms, 90% particles) 500keV 1~3A 2µsec 60Hz 3mm 1400~1600 C CeB 6 0.4πmm.mrad 0.6πmm.mrad 17

18 5. Beam Performance (1/6) First SASE lasing at 49nm was successfully observed in June this year. The lasing data showed that the achieved beam brilliance reaches to the target value, 200A/π 2 mm 2 mrad 2. 18

19 5. Beam Performance (2/6) Prototype Target v.s. 8GeV XFEL Target Prototype: Peak Current=800A Normalized Emittance=2πmm.mrad 8GeV XFEL: Peak Current=3kA Normalized Emittance=1πmm.mrad 19

20 5. Beam Performance (3/6) 5.1. Electron Beam Brilliance(1) Angular photon flux v.s. K-value with ID#1. Ratio(Coherent/Spontaneous) ~315 π 2 mm 2 mrad 2 10 estimated by 3D-FEL simulator SIMPLEX A 1250A 1070A 937A Q=0.25nC ε=2πmm.mrad σ δe/e = A 750A Meas K Value 20

21 5. Beam Performance (4/6) 5.1. Electron Beam Brilliance(2) Radiation Intensity v.s. peak current with ID#1 and ID# π 2 mm 2 mrad 2 estimated by 1D-FEL model. Intensity (a.u.) y=a x 1/2 exp(b x 1/3 )+c x Experiment Fitting Curve Electron Beam Charge (nc) 21

22 5. Beam Performance (5/6) 5.2. Lasing Stability Good reproducibility of SASE lasing by reloading machine parameters. E(µJ/pulse) Ave.=0.96µJ/pulse 1σ=0.43µJ/pulse(~45%) Time (sec) 22

23 5. Beam Performance (6/6) 5.3. Beam Stability Orbit ~1/5~1/10 of beam size Energy Stab. (1σ) Frequency Hori. Vert. σ x =13µm σ y =21µm Devitation [mm] 23

24 6. Towards 8-GeV XFEL (1/3) The experimental results show that PARMELA gives a good design guideline in our case and conclude that the beam performance for x-ray FEL is reachable by the smooth extension of the prototype accelerator. 24

25 6. Towards 8-GeV XFEL (2/3) The remaining issues: Optimization of multi-stage bunch compression system Improvement of inverter PS Precise timing system Alignment scheme for photon and electron beam along undulators etc 25

26 6. Towards 8-GeV XFEL (3/3) 26