David Fritz LUSI DOE Review July 23-24, 2007 Damage Considerations 1 Damage Considerations David Fritz FEL Source Propagation Absorbed Energy Dose Damage Processes in Solids Damage Thresholds FLASH Results Summary FEL Source Propagation Absorbed Energy Dose Damage Processes in Solids Damage Thresholds FLASH Results Summary

David Fritz LUSI DOE Review July 23-24, 2007 Damage Considerations 2 Comparison to Synchrotron Sources ParameterAPSLCLS Repetition Rate6,500,000 Hz120 Hz Pulse Length70 ps0.25 ps Average Power1,000 W0.25 W Peak Power2.2 MW8,000 MW Average heat load is not a concern but instantaneous energy deposition must be considered

David Fritz LUSI DOE Review July 23-24, 2007 Damage Considerations 3 FEL Source Propagation A diffraction limited Gaussian source is assumed

David Fritz LUSI DOE Review July 23-24, 2007 Damage Considerations 4 Peak Fluence

David Fritz LUSI DOE Review July 23-24, 2007 Damage Considerations 5 Radiation Dose per Atom

David Fritz LUSI DOE Review July 23-24, 2007 Damage Considerations 6 Solid State Damage Processes Thermal melting Presure effects Spallation Shear Ablation Non-thermal melting Multi-pulse fatigue effects Thermomechanical stress Chemical Phase transition Thermal melting Presure effects Spallation Shear Ablation Non-thermal melting Multi-pulse fatigue effects Thermomechanical stress Chemical Phase transition

David Fritz LUSI DOE Review July 23-24, 2007 Damage Considerations 7 Thermal Damage Thresholds Heat Capacity - Energy required to raise the temperature of one gram of a substance by 1° K. Enthalphy of Transformation (a.k.a. Latent Heat) – the amount of energy released or absorbed by a substance during a change of phase. Heat Capacity - Energy required to raise the temperature of one gram of a substance by 1° K. Enthalphy of Transformation (a.k.a. Latent Heat) – the amount of energy released or absorbed by a substance during a change of phase.

David Fritz LUSI DOE Review July 23-24, 2007 Damage Considerations 8 Thermal Damage Thresholds (2) BerylliumSilicon

David Fritz LUSI DOE Review July 23-24, 2007 Damage Considerations 9 Thermal Damage Thresholds (3) MaterialDose to T melt † Dose to Melt † Dose in NEH3 † *Dose in FEH1 † * Be B Al Si Ti Cu Ge Mo Ag Ta W Pb * 8265 eV Photon Energy, 1.1 x ph/pulse † Units of eV/atom

David Fritz LUSI DOE Review July 23-24, 2007 Damage Considerations 10 FLASH Results 32.5 nm wavelength 25 fs pulse duration 5.5 μ J pulse energy B4C, C, Si, SiC were exposed to focused FLASH FEL Up to 2.2 J/cm 2 Threshold for surface damage is on the order of the fluence required for themal melting 32.5 nm wavelength 25 fs pulse duration 5.5 μ J pulse energy B4C, C, Si, SiC were exposed to focused FLASH FEL Up to 2.2 J/cm 2 Threshold for surface damage is on the order of the fluence required for themal melting S. Hau-Riege et al., Applied Physics Letters 90, (2007).

David Fritz LUSI DOE Review July 23-24, 2007 Damage Considerations 11 Summary Instantaneous energy deposition must be considered High melting point, low-Z materials will be most resistent to damage Thermal model predicts that some materials can be safely placed in the NEH and FEH beam at normal incidence FLASH damage results are consistent with the thermal model Instantaneous energy deposition must be considered High melting point, low-Z materials will be most resistent to damage Thermal model predicts that some materials can be safely placed in the NEH and FEH beam at normal incidence FLASH damage results are consistent with the thermal model