[email protected] ICRS-11 / RPSD-2008 Mario Santana Leitner FLUKA SIMULATIONS of the radiation damage of permanent magnets M. Santana Leitner,

[email protected]@slac.stanford.eduICRS-11 / RPSD-2008

Mario Santana Leitner

FLUKA SIMULATIONSof the radiation damage of permanent magnets

M. Santana Leitner, J. Vollaire, A. Fassò,

S. X. Mao and Sayed RokniRadiation Protection Department

Stanford Linear Accelerator Center

LCLS Undulator Magnet Irradiation Sensitivity WorkshopSLAC, June 19 2008


Mario Santana Leitner- 2 / 27 -

Advanced 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



LCLS Undulator Radiation damageScheme of work

[email protected]@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.



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%.

[email protected]





Irradiation Experiment(T-493) Spokesman: Heinz-Dieter Nuhn




Irradiation ExperimentIrradiation Experiment (T-493) Spokesman: Heinz-Dieter Nuhn

FLUKA Simulations: Joachim Vollaire

FLUKA simulations [J]MEASUREMENTS: delta B [T]


Dep

osi

ted

En

erg

y [J

]

Mag

net

izat

ion

Lo

ss [

T]

Measurements and simulations along a ‘diameter’ in

each of the magnets



Neutron fluence [n/cm2]

Rel

ativ

e M

agn

etiz

atio

n L

oss

[%

]



FLUKA analysis: Alberto Fassò & Joachim Vollaire


`

`

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 (90o)

Higher damage: M1-M4 (axis)

Possible cause for the two different

regimes: 900 GDR neutrons (low E)

0o high energy neutrons and other

hadrons

For 0.01 % demagnetization: 6E12 n/cm2 (slow)1.67E-15 [%dm/n/cm2]

~E11 n/cm2 (fast) ~E-13 [%dm/n/cm2]





FLUKA analysis: Alberto Fasso & Joachim Vollaire


Non Electromagnetic Dose [Gy]

Rel

ativ

e M

agn

etiz

atio

n L

oss

[%

]

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]



H.D. Nuhn & metrology at SLAC



TDUND stopper and shielding

Radiation from TDUND

A B

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



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’



LCLS Undulator Damage from TDUNDPRELIMINARY RESULTS. UNDULATOR ROLLED OUT

Simulation for beam parked at tdund.

1st 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/cm2/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



LCLS Undulator Damage from TDUNDROLLED IN | ROLLED OUT

The electromagnetic dose is reduced by about a factor 10

The none-EM dose is reduced by a factor ~2



LCLS Undulator Damage from TDUNDFIRST MODULE | SECOND MODULE

The dose decreases very rapidly from the first segment to the

second.



LCLS Undulator Damage from TDUNDIRRADIATION PATTERN

Electromagnetic dose in first

module, first magnet



LCLS Undulator Damage from BFW

Need to validate optical

transport



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

Documents

[email protected] ICRS-11 / RPSD-2008 Mario Santana Leitner FLUKA SIMULATIONS of the radiation damage of permanent magnets M. Santana Leitner,