J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008 Radiation Damage Study at FLASH using the Diagnostic Undulator J. Pflüger, J. Skupin,

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


Overview

• The FLASH Diagnostic or “Sacrificial” Undulator

• Dose Measurements• Observed Demagnetization• TTF1 Results Revisited• FEL Damage Theory and Simulations • Life expectancy• Conclusions


The Diagnostic Sacrificial Undulator




Radiation Dose Measurements


12 / 2004 - 4 / 2008

Measurement


Demagnetization Measurements





TTF1 Results (1999-2002) Revisited

J. Pflüger, B. Faatz, M. Tischer, T. Vielitz NIMA 507 (2003), 186,


TTF1 Undulator System 1999-2002

1999 On Axis Collimator System

From: J. Pflüger, B. Faatz, M. Tischer, T. Vielitz NIMA 507 (2003), 186,


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


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


Field Difference Before-After Installation

Positions of Focusing Magnets for the FODO Lattice (In Total 10)

Conclusion: No detectable Radiation Damage up to 12000Gy


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



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!



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



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



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.


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


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


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


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!


The End

Documents

J. Pflüger / DESY - Radiation Damage Workshop Stanford June 19, 2008 Radiation Damage Study at FLASH using the Diagnostic Undulator J. Pflüger, J. Skupin,