Radiation Damage Study at FLASH using the Diagnostic Undulator

1. Radiation Damage Study at  FLASH using the Diagnostic Undulator J. Pflüger, J. Skupin, B. Faatz, Y. Li, T. Vielitz DESY, Hamburg

2. Overview • The FLASH Diagnostic or “Sacrificial” Undulator • Dose Measurements • Observed Demagnetization • TTF1 Results Revisited • FEL Damage Theory and Simulations • Life expectancy • Conclusions J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

3. The Diagnostic Sacrificial Undulator J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

4. J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

5. J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

6. Radiation Dose Measurements J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

7. J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

8. 12 / 2004 - 4 / 2008

9. Measurement

10. Demagnetization Measurements J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

11. J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

12. J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

13. J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

14. TTF1 Results (1999-2002) Revisited J. Pflüger, B. Faatz, M. Tischer, T. Vielitz NIMA 507 (2003), 186, J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

15. TTF1 Undulator System 1999-2002 From: J. Pflüger, B. Faatz, M. Tischer, T. Vielitz NIMA 507 (2003), 186, 1999 On Axis Collimator System J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

16. 0.3m FLASH Collimator System • Well separated Axes of Accelerator and Undulator (300mm) • Provides Phase Space and Energy Collimation • Apertures fully integrated into Dogleg • Collimator does not shine into Undulators • Very effective for radiation protection J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

17. FLASH: Three representative weekly dose readings 12 / 2004 - 4 / 2008 Sacrificial Undulator J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

18. Field Difference Before-After Installation Positions of Focusing Magnets for the FODO Lattice (In Total 10) Conclusion: No detectable Radiation Damage up to 12000Gy J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

19. TTF1 Revisited Model for Dose Results: 2 x 10-4 / kGy Test Undulator at FLASH: 5 x 10-4 / kGy Symmetric Parabola Observed Difference proportional to Dose Demagnetization J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

20. FEL Simulations Undulator Errors and FEL PerformanceYuhui Li, Bart Faatz Joachim Pflüger Reference:Y. Li, B. Faatz, J. Pflueger, Proceedings of the FEL07 Aug 26-31 Novosibirsk, Russia

21. SASE FEL bandwidth 2ρ For XFEL Δ g < 1 μm ΔT < 0.08°C Traditional: Tolerance Estimation using the Pierce Parameter Resonance condition: • If this criterion is fulfilled no gain degradation is expected! Very stringent requirements on undulator precision and temperature stability

22. Phase shake --- correlation to power degradation Periodic Field Error SASE1 : Error period length GENESIS 1.3  depends on K0, u and error geometry = 39.7 rad/m for u=35.6mm, K0= 3.3 and sinusoidal error function • Field calculated for different periodic errors • Power Loss calculated by GENESIS 1.3 • RMS Phase shake calculated by formula

23. K K ΔK ΔK z z λδ1 λδ2 …… = λδ K K …… = λδ λδ1 λδ2 ΔK ΔK z z λδ1 λδ2 λδ3 …… = λδn λδ1 λδ1 …… = λδn Phase shake analytical calculation For all of the four errors analyzed , • For the same phase shake (same power degradation), large error period means small error strength. Vice versa… • if the error period is small, large error strength (larger than ρ) is permitted

24. K ΔK K0 λδ Z Girder support point Girder support point 1.2m Girder Deformation as a periodic sinusoidal error • Four Support Points used to minimize girder deformation • Remaining deformation is nearly sinusoidal, the error period δ equals to the support length • Deformation of 1.4429  2m AlMg Alloy 6-7m Result:  =1.2mK/K= .0036  30m = 8.4°10% Power Degr.

25. Parabolic Error Model I Periodic Modulation of Beam Profile.Leads to “Periodic” Damage Profile “Periodic” Damage Profile leads to…periodic Modulation of K Periodic Function J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

26. Limits: 10% Loss  .2-.28rad or 11-16° 10% Loss  0.4- 0.7% loss of K/K Parabolic Error Model II Calculate Phase Shake and Power Loss Damage Rate: 5x10-4 /kGy 10% Level 0.4 / 0.7% 10% Dose 8 / 14 kGy J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

27. Lifetime Estimate for FLASH Average Dose over Time 2kGy/a 1.2kGy/a 0.3kGy/a Assumptions: Max.Tolerable K/K (6nm , 10% Loss)  0.5% Resulting 10% Dose : 8 kGy Ave Dose. 2005-2007: 2.0 kGy/a,  40Gy/week Ave Dose. 2005-2008: 1.2 kGy/a  23Gy/week Future Dose: 0.3 kGy/a  6Gy/week J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

28. Summary • Radiation induced Demagnetization observed at FLASH! • With good will also visible at TTF1 in 2002 • Damage rates range from 5 x 10-4 / kGy • FEL Simulation: Exercise for Li’s periodic Error Theory It is shown that this corresponds to 10% Power Loss levels of 8-14 kGy • Life time is expected to be > 8 and < 26.7 years! J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008

29. The End J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008