1. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner FLUKA SIMULATIONS of the radiation damage of permanent magnets M. Santana Leitner, J. Vollaire, A. Fassò, S. X. Mao and Sayed Rokni Radiation Protection Department Stanford Linear Accelerator Center LCLS Undulator Magnet Irradiation Sensitivity Workshop SLAC, June 19 2008

2. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 2 / 27 -  A dvanced multi-particle MONTE CARLO codes (i.e. FLUKA, MARS), are readily used in radiation protection and also in machine protection.  Ability to describe in detail multiple complex 3D objects  Flexible ‘detector’ setup.  Various scoring quantities: dose, energy deposition, fluence, etc.  The mechanism of damage to permanent magnets is not yet know, meaning that the MONTE CARLO code cannot yet predict magnet lifetimes.  By comparing experimental measurements and simulated values, a response function could be extracted.  This function could then be used by the Monte Carlo code to predict the damage of magnets in arbitrary circumstances, i.e. LCLS:  Damage from TDUND  Damage from BFW  Missteering Introduction

3. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner LCLS Undulator Radiation damage Scheme of work nuhn@slac.stanford.edu  LCLS undulators produce FEL with Nd-Fe-B magnets.  Radiation alters the magnetization of permanent magnets.  The exact damaging mechanism is not fully understood. It can depend on: Magnet type, irradiation pattern.  An on-site irradiation experiment was conducted to extract the radiation / demagnetization response function for LCLS magnets and radiation field conditions.  Detailed FLUKA simulations were run for LCLS TDUND  FLUKA results are scaled with the demagnetization response function.  Further experiments + analysis planned.

4. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner Irradiation Experiment (T-493) Spokesman: Heinz-Dieter Nuhn A 13.6 GeV electron beam is stopped in a copper dump, and 9 samples of magnet material are positioned at different distances from the dump. The layout to achieve a range of doses is calculated using FLUKA. The radiation absorbed will be measured by dosimeters. Magnetization will be measured before and after exposure. The integrated beam current will be needed to be recorded to 10%. A 13.6 GeV electron beam is stopped in a copper dump, and 9 samples of magnet material are positioned at different distances from the dump. The layout to achieve a range of doses is calculated using FLUKA. The radiation absorbed will be measured by dosimeters. Magnetization will be measured before and after exposure. The integrated beam current will be needed to be recorded to 10%. nuhn@slac.stanford.edu nuhn@slac.stanford.edu

5. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 5 / 27 - nuhn@slac.stanford.edu Irradiation Experiment (T-493) Spokesman: Heinz-Dieter Nuhn

6. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 6 / 27 - nuhn@slac.stanford.edu Irradiation Experiment Irradiation Experiment (T-493) Spokesman: Heinz-Dieter Nuhn FLUKA Simulations: Joachim Vollaire FLUKA simulations [J]MEASUREMENTS: delta B [T] vollaire@slac.stanford.edu Deposited Energy [J] Magnetization Loss [T] Measurements and simulations along a ‘diameter’ in each of the magnets

7. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 7 / 27 - Neutron fluence [n/cm 2 ] Relative Magnetization Loss [%] nuhn@slac.stanford.edu Irradiation Experiment Irradiation Experiment (T-493) Spokesman: Heinz-Dieter Nuhn FLUKA analysis: Alberto Fassò & Joachim Vollaire fasso@slac.stanford.edu fasso@slac.stanford.edu ` `  Neutron fluence would be a useful indicator:  Better statistics  Can be scored in air  However, in the simulations a clear position dependence was found:  Lower damage: M5-M7 (90 o )  Higher damage: M1-M4 (axis)  Possible cause for the two different regimes:  90 0  GDR neutrons (low E)  0 o  high energy neutrons and other hadrons  For 0.01 % demagnetization:  6E12 n/cm 2 (slow)  1.67E-15 [%dm/n/cm 2 ]  ~E11 n/cm 2 (fast)  ~E-13 [%dm/n/cm 2 ]

8. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 8 / 27 - nuhn@slac.stanford.edu Irradiation Experiment Irradiation Experiment (T-493) Spokesman: Heinz-Dieter Nuhn FLUKA analysis: Alberto Fasso & Joachim Vollaire fasso@slac.stanford.edu fasso@slac.stanford.edu Non Electromagnetic Dose [Gy] Relative Magnetization Loss [%] Total Dose [Gy]  Damage grows with total dose and non-electromagnetic dose but for this data set no clear function can be inferred.  Maximum allowed demagnetization for LCLS undulator magnets ~0.01%   3000 [Gy] total dose  3.33E-6 [% dm]/[tot Gy]   20 [Gy] non electromagnetic dose  5E-4 [% dm]/[non EM Gy]

9. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 9 / 27 - H.D. Nuhn & metrology at SLAC

10. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 10 / 27 - TDUND stopper and shielding Radiation from TDUND AB C A) Self-shielding of can, B) cover of can and C) cover of pneumatic system on top of the can (real models used in the simulations). A B C X Y Z=51299 D A+B TDUND Z (51299 cm) cross section of the tdund inner assembly with the stopper (TDUND), the steel can and its cover (A+B, C) and the 5%- borated polyethylene shielding (D) located inside the cover, around the pneumatic actuator, pipes and cables (not shown). C

11. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 11 / 27 - Lateral shielding of TDUND Radiation from TDUND  ~ 1m long lead block: attenuate muons  Concrete support  Aisle marble plate (gammas)  Steel supports  Main neutron shielding: 5% -borated polyethylene  Marble wrapping to attenuate gammas Plots generated from FLUKA input through ‘simplegeo’

12. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 12 / 27 - LCLS Undulator Damage from TDUND PRELIMINARY RESULTS. UNDULATOR ROLLED OUT  Simulation for beam parked at tdund. 1 st magnet of segment #1:  Doses:  Total ~ 0.1 Gy/h  lifetime ~ 30000 h  Non-Em ~1.8E-3 Gy/h  lifetime ~ 11000 h  (Total) Neutron fluence: 2.63E7 n/cm 2 /h  Lifetime ~ 6E12 / 2.63E7 = 22800 h  Lifetime ~ E11 / 2.63E7 = 3800 h ~ 1 year of commissioning at 100 % ~ 13 years at 10% duty factor Segment #2: about factor 10 longer lifetime!  Other considerations:  The undulator segments can be rolled away from the beam by 8 cm  The dose changes from one segment to the next

13. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 13 / 27 - LCLS Undulator Damage from TDUND ROLLED IN | ROLLED OUT  The electromagnetic dose is reduced by about a factor 10  The none-EM dose is reduced by a factor ~2

14. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 14 / 27 - LCLS Undulator Damage from TDUND FIRST MODULE | SECOND MODULE  The dose decreases very rapidly from the first segment to the second.

15. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 15 / 27 - LCLS Undulator Damage from TDUND IRRADIATION PATTERN Electromagnetic dose in first module, first magnet

16. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 16 / 27 - LCLS Undulator Damage from BFW Need to validate optical transport

17. msantana@slac.stanford.edu ICRS-11 / RPSD-2008 Mario Santana Leitner - 17 / 27 - 1. M. SANTANA LEITNER et. Al., “Prompt dose study in the LCLS undulator”, SLAC Radiation Physics Note RP-07-05, (2007). 2. D. DOWELL, P. EMMA, J. WELCH, “Electron Beam Loss in the LCLS”, LCLS Physics Requirement Document, 1.1-011, SLAC (2006). 3. A. FASSO, A. FERRARI and P.R. SALA, “Electron-Photon Transport in Fluka: Status,” Proc. Monte Carlo 2000 Conference, Lisbon, October 23--26 2000, A. Kling, F. Barao, M. Nakagawa, L. Tavora and P. Vaz eds., Springer-Verlag Berlin, pp. 159–164 (2001). 4. A. FASSÒ, A. FERRARI, J. RANFT and P.R. SALA, “Fluka: Status and Prospective for Hadronic Applications”, same proceedings, pp. 955–960 (2001). 5. P. EMMA, LCLS Linac Current Beaml-line Design Optics Files, www-ssrl.slac.stanford.edu/lcls/linac/optics 6. S. ROESLER and G.R. STEVENSON, “deq99.f - A Fluka user-routine converting fluence into effective dose and ambient dose equivalent”, Technical Note CERN-SC-2006-070- RP-TN, EDMS No. 809389, CERN (2006). 7. M. PELLICCIONI, “Overview of fluence-to-effective dose and fluence-to-ambient dose equivalent conversion coefficients for high energy radiation calculated using the Fluka code”, Radiation Protection Dosimetry, 88, pp. 279–297 (2000). 8. N.V. Mokhov, “The Mars Code System User's Guide”, Fermilab-FN-628 (1995). 9. O.E. Krivosheev, N.V. Mokhov, "MARS Code Status", Proc. Monte Carlo 2000 Conf., pp. 943, Lisbon, October 23-26, 2000; Fermilab-Conf-00/181 (2000). 10. N.V. Mokhov, "Status of MARS Code", Fermilab-Conf-03/053 (2003). 11. N.V. Mokhov, K.K. Gudima, C.C. JAMES et al, "Recent Enhancements to the MARS15 Code", Fermilab-Conf-04/053 (2004). 12. M. SANTANA LEITNER, A. FASSÒ, “Studies on Bremsstrahlung sources in the LCLS undulator”, SLAC Radiation Physics Note RP-07-04 (2007). 13. T. SANAMI, M. SANTANA LEITNER, X.S. MAO, and W.R. NELSON, “Calculation of Energy Distribution and Instantaneous Temperature Rise for the Design of the LCLS 5 kW Electron Dump”, Radiation Physics Note, RP-07-16, SLAC (2007). 14. A. FASSÒ, “Dose Absorbed in LCLS Undulator Magnets”, Radiation Physics Note, RP-05-05, SLAC (2005). 15. M. Santana, J. Vollaire, “Shielding design for LCLS tdund”, Radiation Physics Note, RP-08-to be published, SLAC (2005). 16. J. Vollaire, Johannes Bauer, M. Santana Leitner, FLUKA calculations for the T493 experiment, SLAC Radiation Physics Note RP-07-to be published. 17. T493 irradiation experiment at ES-A, SLAC, to be published. 18. T. Kawakubo, E. Nakamura, M. Numajiri, M. Aoki, T. Hisamura and E. Sugiyama, Permanent Magnet Generating High and Variable Septum Magnetic Field and its deterioration by Radiation, Proc. EPAC 2004, July 5–9 2004, Lucerne, Switzerland, p. 1696–1698 19. H. Schlarb, Collimation System for the VUV Free-Electron Laser at the TESLA Test Facility, PhD Thesis, Hamburg University, 2001