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J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008
Radiation Damage Study at FLASH using the Diagnostic Undulator
J. Pflüger, J. Skupin, B. Faatz, Y. Li, T. Vielitz
DESY, Hamburg
J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008
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
The Diagnostic Sacrificial Undulator
J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008
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
TTF1 Undulator System 1999-2002
1999 On Axis Collimator System
From: J. Pflüger, B. Faatz, M. Tischer, T. Vielitz NIMA 507 (2003), 186,
J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008
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
0.3m
J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008
FLASH: Three representative weekly dose readings
Weekly Dose
0,00
5,00
10,00
15,00
20,00
25,00
30,00
35,00
40,00
45,00
50,00
1/1 1/2 1/3 1/4 1/5 2/1 2/2 2/3 2/4 2/5 3/1 3/2 3/3 3/4 3/5 4/1 4/2 4/3 4/4 4/5 5/1 5/2 5/3 5/4 5/5 6/1 6/2 6/3 6/4 6/5
Meßstelle
Do
sis
(S
v)
25.07.06
22.04.08
16.04.08
12 / 2004 - 4 / 2008
Sacrificial Undulator
J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008
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
TTF1 Revisited
Model for Dose
Symmetric Parabola
Observed Difference proportional to Dose
Demagnetization
Results: 2 x 10-4 / kGy
Test Undulator at FLASH:
5 x 10-4 / kGy
XFELThe EuropeanX-Ray Laser Project X-Ray Free-Electron Laser
Joachim Pflueger, DESYSTI Presentation October 10, 2007
Undulator Errors and FEL Performance
Yuhui Li, Bart Faatz Joachim Pflüger
Reference:Y. Li, B. Faatz, J. Pflueger, Proceedings of the FEL07 Aug 26-31 Novosibirsk, Russia
FEL Simulations
Joachim Pflueger, DESYSTI Presentation October 10, 2007
XFELThe EuropeanX-Ray Laser Project X-Ray Free-Electron Laser
Traditional: Tolerance Estimation using the Pierce Parameter
Very stringent requirements on undulator precision and temperature stability
2ρ
Resonance condition:
)1(2
22
Kus
Δ g < 1 μmΔT < 0.08°C
410~ For XFEL
SASE FEL bandwidth
K
K
K
KK
s
s
2
1
22
• If this criterion is fulfilled no gain degradation is expected!
Joachim Pflueger, DESYSTI Presentation October 10, 2007
XFELThe EuropeanX-Ray Laser Project X-Ray Free-Electron Laser
Phase shake --- correlation to power degradation
• Field calculated for different periodic errors
• Power Loss calculated by GENESIS 1.3• RMS Phase shake calculated by formula
SASE1
0K
K
depends on K0, u and error geometry = 39.7 rad/m for u=35.6mm, K0= 3.3 and sinusoidal error function
)()()( zfKKzfKKzK
Periodic Field Error
: Error period length
GENESIS 1.3
Joachim Pflueger, DESYSTI Presentation October 10, 2007
XFELThe EuropeanX-Ray Laser Project X-Ray Free-Electron Laser
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
0K
K
20
20
tan
sin
;12
1;
180
1
;120
1;
22
1
KkAAA
AA
stconssawtooth
triangleus
λδ1 …… = λδn
z
K
ΔK
λδ1λδ1 …… = λδ
z
K
ΔK
λδ2
λδ1 λδ2 …… = λδ
z
K
ΔK
λδ1 …… = λδn
z
K
ΔK
λδ2 λδ3
89.3:1:23.1:51.1::: tansin tconssawtoothtriangleus
Joachim Pflueger, DESYSTI Presentation October 10, 2007
XFELThe EuropeanX-Ray Laser Project X-Ray Free-Electron Laser
Girder Deformation as a periodic sinusoidal error
Magnet attract Magnet attract
Girder support point
Magnet attract Magnet attract
Girder support point
K
K0 λδZ
ΔK1.2m
• 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 2m AlMg Alloy 6-7m
Result:
=1.2mK/K= .0036 30m = 8.4°10% Power Degr.
J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008
Parabolic Error Model I
)()( and 0for 2
2)(
22
zfzfzzzf
Periodic Function
Periodic Modulation of Beam Profile.Leads to “Periodic” Damage Profile
“Periodic” Damage Profile leads to…periodic Modulation of K
J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008
Parabolic Error Model II
10% Loss .2-.28rad or 11-16°
Limits:
10% Loss 0.4- 0.7% loss of K/K
Damage Rate: 5x10-4 /kGy 10% Level 0.4 / 0.7% 10% Dose 8 / 14 kGy
Calculate Phase Shake and Power Loss
J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008
Lifetime Estimate for FLASH
2kGy/a
Average Dose over Time
0.3kGy/a
1.2kGy/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
Est. Lifetime [Years]
4 (pessimistic)
6,7
17.3
Future:
26.7
J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008
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!