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Damage Considerations David Fritz. FEL Source Propagation Absorbed Energy Dose Damage Processes in Solids Damage Thresholds FLASH Results Summary. Comparison to Synchrotron Sources. Average heat load is not a concern but instantaneous energy deposition must be considered. - PowerPoint PPT Presentation
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David [email protected]
LUSI DOE Review July 23-24, 2007Damage Considerations 1
Damage ConsiderationsDavid Fritz
Damage ConsiderationsDavid Fritz
FEL Source Propagation Absorbed Energy DoseDamage Processes in SolidsDamage ThresholdsFLASH ResultsSummary
FEL Source Propagation Absorbed Energy DoseDamage Processes in SolidsDamage ThresholdsFLASH ResultsSummary
David [email protected]
LUSI DOE Review July 23-24, 2007Damage Considerations 2
Comparison to Synchrotron SourcesComparison to Synchrotron Sources
Parameter APS LCLS
Repetition Rate 6,500,000 Hz 120 Hz
Pulse Length 70 ps 0.25 ps
Average Power 1,000 W 0.25 W
Peak Power 2.2 MW 8,000 MW
Average heat load is not a concern but instantaneous energy deposition must be considered
Average heat load is not a concern but instantaneous energy deposition must be considered
David [email protected]
LUSI DOE Review July 23-24, 2007Damage Considerations 3
FEL Source PropagationFEL Source Propagation
2/12
0
1)(
z
zzW
2
00
Wz
Distance
rangeRayleigh
waistbeamGaussian
0
z
z
W
A diffraction limited Gaussian source is assumed
A diffraction limited Gaussian source is assumed
David [email protected]
LUSI DOE Review July 23-24, 2007Damage Considerations 4
Peak FluencePeak Fluence
densityphoton Peak
densityPhoton
pulse ain photons ofNumber
)(
2)(
2
)()(
),,(
)(),,(
2
2
)(2
2
22
peak
photon
peak
peak
photon
zw
yx
peakphoton
A
N
zw
NzA
zwzA
dydxzyxN
ezAzyx
David [email protected]
LUSI DOE Review July 23-24, 2007Damage Considerations 5
Radiation Dose per AtomRadiation Dose per Atom
photoionpeakphoton AEDose section crossron photoelect Atomic
energyPhoton
photoion
photonE
David [email protected]
LUSI DOE Review July 23-24, 2007Damage Considerations 6
Solid State Damage ProcessesSolid State Damage Processes
Thermal meltingPresure effects
SpallationShear
AblationNon-thermal melting
Multi-pulse fatigue effectsThermomechanical stressChemical Phase transition
Thermal meltingPresure effects
SpallationShear
AblationNon-thermal melting
Multi-pulse fatigue effectsThermomechanical stressChemical Phase transition
David [email protected]
LUSI DOE Review July 23-24, 2007Damage Considerations 7
Thermal Damage ThresholdsThermal Damage Thresholds
M
R
T
T
TM dTCD QdTCDM
R
T
T
M
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.
meltingofheatLatent
etemperaturMelting
etemperaturRoom
heatSpecific
melttoDose
etemperaturmeltingreachtoDose
Q
T
T
C
D
D
M
R
M
TM
David [email protected]
LUSI DOE Review July 23-24, 2007Damage Considerations 8
Thermal Damage Thresholds (2)Thermal Damage Thresholds (2)
Beryllium Silicon
David [email protected]
LUSI DOE Review July 23-24, 2007Damage Considerations 9
Thermal Damage Thresholds (3)Thermal Damage Thresholds (3)
Material Dose to Tmelt † Dose to Melt † Dose in NEH3 † * Dose in FEH1 † *
Be 0.34 0.42 0.0002 0.00004
B 0.54 1.06 0.0005 0.0001
Al 0.19 0.30 0.03 0.007
Si 0.37 0.89 0.04 0.01
Ti 0.50 0.65 0.24 0.06
Cu 0.31 0.45 0.15 0.03
Ge 0.29 0.68 0.12 0.03
Mo 0.93 1.32 0.36 0.08
Ag 0.41 0.43 0.56 0.13
Ta 0.98 1.36 0.72 0.16
W 1.24 1.78 0.76 0.17
Pb 0.09 0.14 1.17 0.26
* 8265 eV Photon Energy, 1.1 x 1012 ph/pulse† Units of eV/atom
David [email protected]
LUSI DOE Review July 23-24, 2007Damage Considerations 10
FLASH ResultsFLASH Results
32.5 nm wavelength25 fs pulse duration5.5 μJ pulse energyB4C, C, Si, SiC were exposed to focused FLASH FELUp to 2.2 J/cm2
Threshold for surface damage is on the order of the fluence required for themal melting
32.5 nm wavelength25 fs pulse duration5.5 μJ pulse energyB4C, C, Si, SiC were exposed to focused FLASH FELUp to 2.2 J/cm2
Threshold for surface damage is on the order of the fluence required for themal melting
S. Hau-Riege et al., Applied Physics Letters 90, 173128 (2007).
David [email protected]
LUSI DOE Review July 23-24, 2007Damage Considerations 11
SummarySummary
Instantaneous energy deposition must be consideredHigh melting point, low-Z materials will be most resistent to damageThermal model predicts that some materials can be safely placed in the NEH and FEH beam at normal incidenceFLASH damage results are consistent with the thermal model
Instantaneous energy deposition must be consideredHigh melting point, low-Z materials will be most resistent to damageThermal model predicts that some materials can be safely placed in the NEH and FEH beam at normal incidenceFLASH damage results are consistent with the thermal model
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