Feasibility Studies undulator - Stanford University · 2012. 3. 5. · Content • Technical challenges • Feasibility studies: ⇒ reﬂectivity of diamond crystals ⇒ heat load

48th ICFA Advanced Beam Dynamics Workshop on Future Light SourcesMarch 1-5, 2010, SLAC, Menlo Park, California

XFELO X-ray Cavity

Feasibility Studies

Yuri Shvyd’ko

C1

C2 C3

C4

M1

M2

e-

undulator x-rays

Content

• Technical challenges• Feasibility studies:

⇒ reflectivity of diamond crystals⇒ heat load problem⇒ nanoradian angular stabilization⇒ radiation damage

• Conclusions and Outlook

Yu. Shvyd’ko FLS2010, SLAC, March 1, 2010

XFEL Oscillator

x-rays

e-

Beam

dump

Linac

undulator

Permeablemirror

R1, T1

Mirror

R2 L 100 m

XFELO requires:

• ultra-low-emittance (εn . 10−7 m rad) electron beams,• low-loss x-ray crystal cavity (losses ' 15%) R1, R2 > 95%, T1 ' 4%

K.-J. Kim, Yu. Shvyd’ko, S. Reicher, PRL 100 (2008) 244802.


Reflectivity of Si in backscattering

0 5 10 15

0.75

0.8

0.85

0.9

0.95

1.0

Si@120 K

0 5 10 15

0.75

0.8

0.85

0.9

0.95

1.0

Si@300 K

E [keV]

Refl

ecti

vit

y


Theory predicts highest reflectivity from diamond

0 5 10 15

0.75

0.8

0.85

0.9

0.95

1.0

C@300 K

E [keV]

Refl

ecti

vit

y

Very high reflectivity (in theory)due to:

• High Debye Temperature, andthus high Debye-Waller factor

• Low Z, low photo absorption


undulator

L

S

H

H

2

2

A

B

M2

M1

e-

x-rays

RA × RB × RM1 × RM2 ' 0.9 TA ' 0.04

Diamond cavity for the X-FEL Oscillator


Diamond crystal and mirror reflectivity @ 12 keV

0.0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Tra

nsm

issi

vit

y

Ab

sorp

tio

n

-60 -40 -20 0 20 40 60

E - E0

[meV]

0.0

0.2

0.4

0.6

0.8

1.0

Refl

ecti

vit

y

E0=12.0404 keV

0.0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Tra

nsm

issi

vit

y

Ab

sorp

tio

n

-60 -40 -20 0 20 40 60

E - E0

[meV]

0.0

0.2

0.4

0.6

0.8

1.0

Refl

ecti

vit

y

E0=12.0404 keV

Mirror calculations:www-cxro.lbl.gov

Narrow band mirrors:∆E ≈ 10 meV; ∆E ≈ ~/τp


undulator

L

S

H

H

2

2

A

B

M2

M1

e-

x-rays

E = EH cos Θ ⇒ Two-crystal scheme is not tunable.

Because, it is necessary to keep small φ . 2 mrad

and therefore small Θ . 2 mrad, for high reflectivity of the mirrors.

Two-Crystal Cavity is not Tunable


A four-crystal (A,B,C, and D) x-ray optical cavity allows photon energy E tuningin a broad range by changing the incidence angle Θ.

A

B C

D

M1

M2

e-

undulator

L

L’

S

G

G

F

H

H

H

2

2

x-rays

R.M.J. Cotterill, Appl. Phys. Lett., 12 (1968) 403

K.-J. Kim, and Yu. Shvyd’ko, Phys. Rev. STAB (2009)

E = EH cos Θ

Tunable Cavity


A

B C

D

M1

M2

e-

undulator

H

H

H

2

2

x-rays

X-ray Optics:

• Quality of diamond crystals:• is the theoretical reflectivity achievable?

• Heat load problem (reflection region variations . 1 meV).• Angular stability: δθ . 10 nrad (rms)• Spatial stability: δL . 3 µm (rms) → δL/L . 3 × 10−8

• Radiation damage

XFELO Technical Challenges


Quality of Diamond crystals


3rd International Conference on Diamonds for Modern Light Sources, Awaji Yumebutai, 20th-23th May 2008ESRF15

Phase platePhase plate

White beam topograph in transmission

7.1 mm

110-oriented plate

Dislocation free areas of 4x4mm2

and more!!!

1-1-1-reflection

Härtwig, 2008 (ESRF)

Required diamond crystals:• high quality (dislocation free, etc.)• thickness: 20 − 2000 µm• small suffice: ' 1 mm2

Still open question:is the theoretical reflectivity achievable?

Quality of Diamond crystals


undulator

x-rays

bandwidth100 eV

C(111) cooledmonochromator

bandwidth1.7 eV

2 Si(220)

300 K

2 Si(220)

300 K

Si(15 11 9) channel-cut

123 K

T. Toellner

bandwidthE 1 meV

high-resolutionmonochromator

E=23.7 keV

(111)

(995)2

= 2 10-4

APD

diamond

L 10 mT. Toellner

Shvyd’ko, Stoupin, Cunsolo, Said, Huang, Nature Phys. 6, 196 (2010)

Experiment, 30-ID @ APS


10-3

2

5

10-2

2

5

10-1

2

5

1

Refl

ecti

vit

y,R

-15 -10 -5 0 5 10 15

E - E0, [meV]

C(995) theoryE

0.2

0.4

0.6

0.8

R

-10 0 10

E - E0

E =2.9 meV

R =91 %

C(995), EH

= 23.765 keV

Lcrystal = 415µm

Rtheory = 91%

Spectral Width and Reflectivity: Theory


10-3

2

5

10-2

2

5

10-1

2

5

1

Refl

ecti

vit

y,R

-15 -10 -5 0 5 10 15

E - E0, [meV]

experimentC(995) theory

E

0.2

0.4

0.6

0.8

R

-10 0 10

E - E0

E =2.9 meV

R =87 %R =91 %

C(995), EH

= 23.765 keV

δE = 1.5 meV

δE = hc/(2Lcrystal)

dcrystal = 415 ± 5µm

Rtheory = 91%

Rexperiment = 87%

Beam footprint' 1 mm2

Shvyd’ko, Stoupin, et al, Nature Phys. 6, 196 (2010)

Spectral Width and Reflectivity: Experiment


0.92

0.94

0.96

0.98

1.0

Peak

Refl

ectiv

ity

5 10 15 20 25

2

5

102

2

5

103

2

Pene

trat

ion

Dep

th[

m]

5 10 15 20 25

Bragg Energy EH

[keV]

1

10

102

Ene

rgy

Wid

th[m

eV]

5 10 15 20 25

R, L, and ∆E are interconnected. ∆E ∝ 1/L

R L ∆E

Smallness of ∆E is a hallmark of high quality crystal

Reflectivity vs. Penetration & Energy Width


0 1 2 3 4 5x [mm]

0

1

2

3

4

5

6

7

8

y[m

m]

(a)

0 1 2 3 4 5x [mm]

0

1

2

3

4

5

6

7

8

1

1.3

2

4

20

Spectral width, E/ Emin

(b)

0 1 2 3 4 5x [mm]

0

1

2

3

4

5

6

7

8

0

0.2

0.4

0.6

0.8

1

Reflectivity, R/Rmax

(c)


Spectral Width and Reflectivity Map


0 1 2 3 4 5x [mm]

0

1

2

3

4

5

6

7

8

y[m

m]

(a)

0 1 2 3 4 5x [mm]

0

1

2

3

4

5

6

7

8

1

1.3

2

4

20

Spectral width, E/ Emin

(b)

0 1 2 3 4 5x [mm]

0

1

2

3

4

5

6

7

8

0

0.2

0.4

0.6

0.8

1

Reflectivity, R/Rmax

(c)


Synthetic diamond crystals are available with theoretically high reflectivity andsufficiently large in size for XFELO cavity applications.

Spectral Width and Reflectivity Map


Heat Load Problem


Temperature gradient δT ⇒ energy spread δE/E = βδT .Requirement: δE . 1 meV, when the next pulse arrives.

Incident power ' 50 µJ/pulse.Absorbed power: ' 1 µJ/pulse (2%).Footprint: ' 100 × 100 µm2

Is it a problem?

Heat Load Problem


300

301

0

5

10

15

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Time [ s]

T(0)=300 K

T =0.5 K

= 1 10-6

K-1

Dia

mo

nd

Tem

per

aure

T[K

]

Ph

oto

nE

ner

gy

Sp

read

E[m

eV]

100 m

200 m

beamfootprint

H. Sinn simulations


• Big temperature jump δTafter the x-ray pulse arrival.

• T=300K: Big temperaturespread by the arrival of

Heat Load Problem


300

301

0

5

10

15

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Time [ s]

T(0)=300 K

T =0.5 K

= 1 10-6

K-1

100

105

110

0

2

4

6

8

10

12

14

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Time [ s]

T(0)=100 K

T =14 K

= 1 10-7

K-1

Dia

mo

nd

Tem

per

aure

T[K

]

Ph

oto

nE

ner

gy

Sp

read

E[m

eV]

100 m

200 m

beamfootprint

H. Sinn simulations




the next x-ray pulse.

• T=100K: Negligible temperaturespread by the arrival of


Heat Load Problem


300

301

0

5

10

15

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Time [ s]

T(0)=300 K

T =0.5 K

= 1 10-6

K-1

100

105

110

0

2

4

6

8

10

12

14

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Time [ s]

T(0)=100 K

T =14 K

= 1 10-7

K-1

Dia

mo

nd

Tem

per

aure

T[K

]

Ph

oto

nE

ner

gy

Sp

read

E[m

eV]

100 m

200 m

beamfootprint

H. Sinn simulations


Solution: Maintain diamond at T < 100 K!




• T=100K: Negligible temperaturespread by the arrival of


• Reasons:1. High temperature diffusivity D2. Low temperature expansion β

Heat Load Problem


Diamond Thermal Expansion

10-9

10-8

10-7

10-6

Thermalexpansion,[K-1]

0 50 100 150 200 250 300

T, [K]

Experiment 1 (March 09)Experiment 2 (May 09)

4.0 10-14T3

Polynomial fit

Stoupin, Shvyd’ko, PRL 104, 085901 (2010)


100101102103104105106107108109110111112

0

5

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Time [ s]

T(0)=100 K

T =14 K

= 3.9 10-8

K-1

50

55

60

65

70

75

80

85

90

95

0

2

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Time [ s]

T(0)=50 K

T =40 K

= 3.9 10-9

K-1

Dia

mo

nd

Tem

per

aure

T[K

]

Ph

oto

nE

ner

gy

Sp

read

E[m

eV]

100 m

200 m

beamfootprint

H. Sinn simulations


Solution: Maintain diamond at T < 100 K!

Corrected energy scaleXXy

Heat Load Problem


Angular & Spatial Stability


Required angular stability: δθ . 10 nrad (rms)Required spatial stability: δL . 3 µm (rms) ⇒ δL/L ' 3 × 10−8 (L = 100 m)



Intensity,R(V)

Voltage, VVmaxV0


Solution: Null-detection harware feedback. (LIGO prototype)

X-ray intensity: linear response tosmall angular oscillations is propor-tional to angular deviation from themaximum of the rocking curve.



Intensity,R(V)

Voltage, VVmaxV0

monitoring

Detector

Lock-in amplifier Integrator

piezo driver

piezo actuator

x-ray beam

IN OUT REF OUT IN REF IN OUT OUT

CONROL IN

R(V(t))

V v(t)

V + v(t)

V0+ V +v(t)


Solution: Null-detection harware feedback. (LIGO prototype)

X-ray intensity: linear response tosmall angular oscillations is propor-tional to angular deviation from themaximum of the rocking curve.

Feedback: correction signal is ex-tracted using lock-in amplification.



0

10000

20000

Intensity[a.u.]

-1000 -500 0 500 1000

3 [nrad]

-0.2 -0.1 0.0 0.1 0.2

Voltage [V]

FWHM

3=500 nrad=75mV

Region of stability=50 nrad

1

HHLMHRM

IC2

IC1IC3

APD

3

0Si6

Si5 Si4

Si3 Si2

Si1D2

D1

T. Toellner, D. Shu

HERIX Monochromator Stability Region


a b

0

1 104

2 104

3 104

4 104

5 104

6 104

7 104

8 104

Intensity[a.u.]

-1.0

-0.5

0.0

0.5

1.0

0 10 20 30 40 50 60

Time [minutes]

APDIC1

IC2IC3

HHLMHRM

0

1 104

2 104

3 104

4 104

5 104

6 104

7 104

8 104

-1.0

-0.5

0.0

0.5

1.0

Correctio

nsignal[V]

0 1 2 3 4 5 6 7 8 9 10

Time [hours]

APDIC1

IC2IC3

HHLMHRM

1

HHLMHRM

IC2

IC1IC3

APD

3

0Si6

Si5 Si4

Si3 Si2

Si1D2

D1

T. Toellner, D. Shu

HERIX Monochromator Stabilization


a b

0

1 104

2 104

3 104

4 104

5 104

6 104

7 104

8 104

Intensity[a.u.]

-1.0

-0.5

0.0

0.5

1.0

0 10 20 30 40 50 60

Time [minutes]

APDIC1

IC2IC3

HHLMHRM

0

1 104

2 104

3 104

4 104

5 104

6 104

7 104

8 104

-1.0

-0.5

0.0

0.5

1.0

Correctio

nsignal[V]

0 1 2 3 4 5 6 7 8 9 10

Time [hours]

APDIC1

IC2IC3

HHLMHRM

1

HHLMHRM

IC2

IC1IC3

APD

3

0Si6

Si5 Si4

Si3 Si2

Si1D2

D1

T. Toellner, D. Shu

' 15 nrad (rms) stabilization was demonstratedStoupin, Lenkszus, Laird, Goetze, K-J Kim, Shvyd’ko, RSI (submitted)

HERIX Monochromator Stabilization


Radiation damage in diamond


XFELO generates:

50µJ/pulse @ 12 keV with ' 1 MHz rep. rateFootprint: A = 1.6 × 10−4 cm2 (rms)Flux ' 2 × 1020 ph/s/cm2

Time to ionize carbon atom with 100% probability: T ' 250 s Robin Santra

Can this produce irreversible changes in the perfect crystal lattice structure?



XFELO generates:

50µJ/pulse @ 12 keV with ' 1 MHz rep. rateFootprint: A = 1.6 × 10−4 cm2 (rms)Flux ' 2 × 1020 ph/s/cm2

Time to ionize carbon atom with 100% probability: T ' 250 s Robin Santra

before after 1 yearof operations

APS undulators generate:

Flux ' 5 × 1017 ph/s/cm2

Time to ionize carbon atom with 100% probability: T ′ ' 105 s ' 1 day

Graphitization of the surface layer

of the diamond crystal is ob-served after several daysof operations. Though,no significant degradation in theperformance of the high-heat-load monochromator is observedafter a year of operations.

��9



⇒ Operate diamond at cryogenic temperatures.⇒ Use isotopically pure 12C crystals.

Laser damage threshold is more than order of magnitude higher for isotopicallypure diamond.Anthony et al, PRB, 42 1104 (1990)

⇒ Apply electric fields to keep the electrons in diamond (K-J. Kim)⇒ ....

How to mitigate radiation damage in diamond?


A

B C

D

M1

M2

e-

undulator

H

H

H

2

2

x-rays

X-ray Optics:

• Quality of diamond crystals:• is the theoretical reflectivity achievable?

• Heat load problem: reflection region variations . 1 meV.• Angular stability: δθ . 10 nrad (rms)• Spatial stability: δL . 3 µm (rms) → δL/L . 3 × 10−8

• Radiation damage

XFELO Technical Challenges


Acknowledgments


XFELO collaboration:

Kwang-Je Kim (APS)

Stanislav Stoupin (APS)Ryan Lindberg (APS)Sven Reiche (SLS)Bill Fawley, (LBNL)Frank Lenkszus (APS)Deming Shu (APS)Harald Sinn (European XFEL)

Thanks to:

Robert Winarski (APS)Tim Graber (APS)Robert Laird (APS)Stan Whitcomb (LIGO)Al Macrander (APS)Tim Roberts (APS)Kurt Goetze (APS)Emil Trakhtenberg (APS)Ayman Said (APS)Alessandro Cunsolo (APS)Tom Toellner (APS)Lahsen Assoufid (APS)

Documents

Feasibility Studies undulator - Stanford University · 2012. 3. 5. · Content • Technical challenges • Feasibility studies: ⇒ reﬂectivity of diamond crystals ⇒ heat load