R. TatchynIAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 1 Pulsed Laser Undulators Excited by Compact Storage Rings: A Candidate Technology for

R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03

1

Pulsed Laser Undulators Excited by Compact Storage Rings: A Candidate Technology for Single-shot Medical

Imaging

IAC Workshop on Medical and Biological Imaging with Novel X-Ray Beams

August 8, 2003

*Talk based on work and contributions of numerous investigators at SSRL, University of Oregon, BPI, BNL, DESY, KEK, ESRF, KIPT, and elsewhere

Roman Tatchyn*Stanford Synchrotron Radiation Laboratory

Stanford, CA 94305


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1.TERMINOLOGY: SOURCE PHASE SPACE:

PHASE SPACEDIMENSION

DISTRIBUTIONMEAN

DISTRIBUTIONVARIANCE

HIGHERDISTRIBUTION

MOMENTS

PROBABILITYDENSITY

FUNCTION

x <x> <(x-<x>) 2> ?

y <y> <(y-<y>) 2> ?

z <z> <(z-<z>) 2> ?px <(p x-) 2> ?py <(p y-) 2> ?pz <(p z-) 2> ?

→• • •→• • •→• • •→• • •→• • •→• • •→

E-BEAM DISTRIBUTION PARAMETERSSiingle-electron RadiationCone Distribution Parameters and Relations:

r

rx’ > /2;

ry

ry’ > /2;

rr

f /f > /2


3

Brightness*:(photons per unit phase space)

Key source parameters:

*[photons/s,mm2,mr2,0.1%BW]

Spectral flux:(photons per second, per 0.1% BW)

For a Gaussian e-beam distribution

Here the standard deviations are quadratic concatenations of the e-beam and single-electron radiation-cone standard deviations.

€

B =N phot /σ τ

T

8π 3σ xTσ x '

Tσ yTσ y '

Tσ fT / f

€

(σ fT / f )2 ≅ 4(σ E

e / E )2 + (σ fr / f )2

€

(σ xT )2 = (σ x

e )2 + (σ xr )2

E.g.,


4

Example:


5

Examples:


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(em ittance) (acceptance)(em ittance+acceptance)

(em ittance + acceptance)

• any experiment typically measures the phase space parameters of some particle distribution, to some resolution

• the requirenments are met by designing for the phase space characteristics of the source, x-ray optics, and detector

• Questions: What is the current status of these elements in SR applications related to Medical and Biological Imaging? Are they optimal? Are new directions and technologies in sight?


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Features of conventional coronary K-edge subtraction angiography (moderate resolution):• wiggler source to enable subject scanning in 1D• critical energy substantially lower than IK edge• operation on a high energy storage ring• crystal monochromator• integrated mega-facilities envisaged (Mezentsev et al, Wiedemann, Dix et al)

Possible areas of innovation• short-period insertion devices on compact rings (no harmonics)• single shot imaging (pulsed-mode sources?)• 2D e-beam and/or optical rastering• multilayer optics for harmonic suppression• new imaging techniques, advanced X-ray Optics• one major goal: smaller-scale, economical instruments


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EXAMPLE: Conventional DDSA* imaging

*DDSA: Dual-energy Digital Subtraction Angiography

WIGGLER


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EXAMPLE: Single-shot DDSA imaging based on a Micropole Undulator (MPU) + low energy storage ring*

*P. Csonka and R. Tatchyn, “Short Period Undulators for Human Angiography,” Proceedings of the Workshop on Fourth Generation Sourcrs, M. Cornacchia, H. Winick, eds., SLAC, CA, 2/24-27,1992, SSRL 92/02, pp. 5556-564.

MicropoleUndulator:Magnets

Reduced-Energy Storage Ring

Optics

Solid State PSDDetectorS

Display

Computer

Computer-ControlledChair

SynchrotronRadiation

Electron Beam

Electronics

DichromaticBeam

7-998503A3

MicropoleUndulator:

Laser/Mcrowave Cavity

E

B


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EXAMPLE: An alternative imaging technique (SXI (Paul Csonka)) Imposing novel requirements on optics and the insertion device


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K ≡ 0 . 934

u

[ cm ] B

0

[ T ]

r ( t ) =

K u

γ

sin

β

*

c

u

t

⎛

⎝

⎜

⎞

⎠

⎟, 0 , β

*

ct −

K

u

16 γ

sin

4 β

*

c

u

t

⎛

⎝

⎜

⎞

⎠

⎟

⎛

⎝

⎜

⎞

⎠

⎟

β ( t ) =

β

*

K

γ

cos

2 π β

*

c

λ

u

t

⎛

⎝

⎜

⎞

⎠

⎟, 0 , β

*

−

β

*

K

2

4 γ

2

cos

4 π β

*

c

λ

u

t

⎛

⎝

⎜

⎞

⎠

⎟

⎛

⎝

⎜

⎞

⎠

⎟

˙

β ( t ) = −

c β

*

K

γ u

sin

β

*

c

u

t

⎛

⎝

⎜

⎞

⎠

⎟, 0 ,

c β

*

K

γ

u

sin

4 β

*

c

u

t

⎛

⎝

⎜

⎞

⎠

⎟

⎛

⎝

⎜

⎞

⎠

⎟

K ~ 1 ( undulator )

=

u

γ

1 +

K

⎛

⎝

⎜

⎞

⎠

⎟

K >> 1 ( wiggler )

εc

[ keV ] ≅

3

E

[ GeV ] B0

[ T ]

INSERTION DEVICES


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P =

3

e

c

γ

6

˙ β

( )

− β ×˙ β

( )

⎡

⎣ ⎢

⎤

⎦ ⎥

( C G S )

P ≅

3

e

c

γ

4

˙ β

p e r p( )

.

P =

e

3 c

γ Kc

u

⎛

⎝

⎜

⎞

⎠

⎟

=

e

3 c

Kc( )

1 + K

/ ( )( )

u

For sinusoidal trajectory

Total emitted power (flux):

Motivation for shorter period insertion devices:

=u

2γ 2 1+K2

2

⎛ ⎝ ⎜

⎞ ⎠ ⎟Effect on Brightness (assume fixed K, fixed , fixed device length):

(however, must als oconsider ne t effect of energy reduction on emittance)

• reduce λu g λ’u [ Energy

€

∝

€

λu

'

λu

• in-band flux

€

∝ Nu [ Brightness

€

∝

€

1

λu


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Spectral flux advantage of a short-period (u1) vs. long-period (u2) undulator

• for arbitrary fixed Ku1 ~ Ku2 u1 advantage u2 /u1

• certain technologies (for which u1<< u2) may also limit u1 to Lu1<< Lu2 and Iu1<< Iu2

• however, in that limit factor II above can compensate these factors and reduction in machine energy can be correspondingly enormous.

€

Pu11st

Pu21st ≅

Ku12 (1 + Ku2

2 / 2)Ku2

2 (1+ Ku12 / 2)

⎛ ⎝ ⎜

⎞ ⎠ ⎟I

λ u2

λ u1

⎛ ⎝ ⎜

⎞ ⎠ ⎟II

Lu1

Lu2

⎛ ⎝ ⎜

⎞ ⎠ ⎟III

Iu1

Iu2

⎛ ⎝ ⎜

⎞ ⎠ ⎟IV

€

∝


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Spectral flux advantage of a short-period undulator vs. a wiggler (assume Ku < 0.75)

• if the technology limits Bu ~ Bw then the possibility of making Lw >> Lu can limit the short-period advantage

• radiation-field or pulsed-current technologies may allow Bu to exceed the Bw (of conventional wigglers) by orders of magnitude • a promising technology of the former type appears to be the focused-laser undulator (Bu kT Ku 0.1-1)

€

Pu

Pw

≅3Eu

2Bu2LuIu

Ew2 Bw

2LwIw

≅2Ku

(λ [Å])2

⎛ ⎝ ⎜

⎞ ⎠ ⎟I

Bu

Bw

⎛ ⎝ ⎜

⎞ ⎠ ⎟II

Lu

Lw

⎛ ⎝ ⎜

⎞ ⎠ ⎟III

Iu

Iw

⎛ ⎝ ⎜

⎞ ⎠ ⎟IV


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REFERENCES TO e-BEAM/LASER UNDULATOR SOURCE R&D:

[1] F.R. Arutynian, V.A. Tumanian. 'The Compton effect on relativistic electrons and the possibility of obtaining high energy beams," Phys. Lett., 4 (1963), p. 176-178.

FIRST EXPERIMENT AT CEA:[2] R.H. Milburn. "Electron scattering by an intense polarized photon field," Phys. Rev. Lett. 10 (1963) p. 75-77.[3] L. Federici et. al. “Backward Compton scattering of laser light against high-energy electrons: the LADON

photon beam at Frascati.,” Nuovo Cimento (59B), ser.2, no.2,1980, p.247.

SLAC WORKSHOP ON FOURTH GENERATION LIGHT SOURCES[4] P. L. Csonka, R. Tatchyn, “Short Period Undulators for Human Angiography,” Proceedings of the Workshop on Fourth Generation Light Sources, M. Cornacchia nd H. Winick, eds., SLAC, CA, February 24-27, 1992, SSRL 92/02, pp. 555-564.[5] E. Esarey, P. Sprangle, A. Ting, S.K. Ride, “Laser synchrotron radiation as a compact source of tunable, short pulse hard X-rays,” Nuclear Instruments & Methods in Physics Research, Section A (Accelerators, Spectrometers, Detectors and Associated Equipment); 1 July 1993; vol.A331, no.1-3, p.545-9

LASER/e-BEAM COOLING[6] V. Telnov, “Laser cooling of electron beams for linear colliders,” Phys. Rev. Lett. 78, 1997, p. 4757.

LESR “Laser Electron Storage Ring” PROJECT (SLAC)[7] Z. Huang, R. Ruth, "Laser-electron storage ring," Phys. Rev. Lett.; 2 Feb. 1998; vol.80, no.5, p.976-9.

NESTOR “Next-generation Electron STOrage Ring” PROJECT (KIPT)[8] E. Bulyak, P.Gladkikh, A.Zelinsky at al, ”Compact X-ray source based on Compton scattering,” Nuclear Instr. & Meth. In Phys Research A, 487, 2002, pp. 241-248.:


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Laser Undulator

• features: 1) high rep rate laser 2) cavity length = interbunch spacing 3) ultra-high Q mirror cavity

Stanford/KIPT Project*

*V. Agafonov et al, “Spectral Characteristics of an Advanced X-ray Generator at the KIPT based on Compton Back-scattering,” presented at the 2003 SPIE Annual Meeting, San Diego, CA, Aug. 4, 2003, Conference 5194A.

Figure 1. Layout of the NESTOR storage ring.BM1-4 are bending magnets ,Q1-20 are quadrupole magnets, S1-18 are sextupole magnets, M1-2

are mirrors of an optical resonator


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Parameter Values Units

Laser Wavelength 10600 ÅLaser Pulse Length (FWHM) 0.03 mPeak Laser Pulse Power 210 MWLaser Repetition Rate 10 KHzCavity Mirror Reflectance 0.9999 -Cavity Damping (1/e) Time 0.00022 sCavity Damping Time Duty Factor 80 %Peak Stored Laser Pulse Power 900 MWAverage Stored Laser Pulse Power 360 MWLaser Beam Waist (FWHM) 100 μm

Laser Beam Rayleig hLength 0.03 mPeak Fiel dIntensity 31 TeslaAverag eFiel dIntensity 3 TeslaEquivale nt Average K Parameter 0.003 -

Electro nBeam Energy 100 MeVElectro nBeam γ 196 -

Electro nEnergy Spre (ad FWHM) 3.5 %Horizont al Emittance 70 n -m radVertical Emittance 70 n -m radHorizont albeta 0.03 mVertical beta 0.05 mHorizont alBeam Size (FWHM) ~100 μm

Vertical Beam Size (FWHM) ~100 μm

KIPT X-Ray Generator Parameters:


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KIPT Spectrum

Radiation far-field target geometry in normalized angle space


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Full angle-integrated spectrum through the 2.5th harmonic. The photon energy spread induced by the electron beam energy spread is 3.5% (rms). Storage ring current ~10 mA. ε1 = 180 keV. The duty factor based on a single 3 cm (FWHM) long electron bunch is ~ 514.

KIPT Spectrum

0

5 10

10

1 10

11

1.5 10

11

2 10

11

0.4 0.8 1.2 1.6 2 2.4

KIPT ANGLE-INTEGRATED AVERAGE

SPECTRAL FLUX DISTRIBUTION

(Single Bunch, K=0.0023, γ∗θ < 10)

ΔΕ/Ε ∼ 0.035

/ ,0.1%Photons s BW

ε [ ]/keV ε1

[ ]keV


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0

5 1010

1 1011

1.5 1011

2 1011

0.4 0.8 1.2 1.6 2 2.4

KIPT ANGLE-INTEGRATED AVERAGE

SPECTRAL FLUX DISTRIBUTION

(Single Bunch, K=0.0023, γ∗θ < 0.41)

ΔΕ/Ε ∼ 0.035

/ ,0.1%Photons s BW

ε [ ]/keV ε1

[ ]keV

KIPT Spectrum

KIPT Compton back-scattering spectrum integrated over the emittance-defined angular aperture of the electron beam through the 2.5th harmonic. The photon energy spread induced by the electron beam energy spread is 3.5% (rms). Storage ring current ~ 10 mA.. ε1 = 180 keV. The duty factor based on a single 3 cm (FWHM) long electron bunch is ~ 514.


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KIPT X-RAY GENERATOR RANGE OF FLUX PERFORMANCE vis-a-vis SPEAR

(The chart at left compares the spectral flux performance of SPEAR vs. the present design of NESTOR. However, NESTOR’s photon energy(~180 keV) is ~21 times greater than SPEAR’s.. Thus, if the ordinate’s units were changed to energy flux the performance markers for NESTOR would need to be shifted upward by more than one decade.


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EXAMPLE: Flux requirements for single-shot DDSA

1) 1000 x 1000 element Position Sensitive Detector (PSD)) 100μ x 100μ detector pe3) ~ 105 photons/pixel/shot (~300 S/N)4) 98% system (optics/patient/detector) losses5) ~1% useful source bandwidth6) 20 ms “single-shot” exposure

SOURCE REQUIREMENTS:

1) ~ 5 x 1012 photons/shot2) ~ 2.5 x 1014 photons/s3) Laser field ~ 500-1000 T4) Laser power ~ 1 TW 50 J stored laser pulse energy


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Pulsed-Cavity Storage Ring (R&D) Requirements:

1) Mirrors (if metal) must be capable of absorbing ~1000 J ( if R ~0.9999) to ~ 10000 J (if R ~ 0.999) without spoiling cavity Q. Either metal or dielectric mirrors must be capable of withstanding the associated electric fields without spoiling the Q.

2) TW laser (system) must be capable of sustaining ~ 10 KhZ rep rate for ~ 20+ ms.

3) Power supply system must provide stored-energy capability of ~ 0.1 - 1 MJ

4) Laser fleld- e-beam interaction must not impact the stored beam lifetime more than fractionally


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Selected References to Short-Period Undulator, Machine, and Optics Technologies R&D at SSRL and SLAC (1984-present):

[1]] R. O. Tatchyn, "Optimum Zone Plate Theory and Design (invited)," in X-Ray Microscopy, Springer Series in Optical Sciences, Volume 43, Springer-Verlag, Berlin, 1984, p.40.[2] R. Tatchyn and P. Csonka, "Submillimeter Period Undulators: New Horizons in Insertion Device Technology (invited),” Proceedings of the Adriatico Research Conference on Undulator Magnets for Synchrotron Radiation\ and Free lectron Lasers, R. Bonifacio, L. Fonda, and C. Pellegrini, eds., ICTP, Trieste, Italy, June 1987, World Scientific, Hong Kong, 1987, p. 39.[3] R. Tatchyn, P. Csonka, and A. Toor, "Micropole Undulators in Accelerator and Storage Ring Technology,” Proceedings of he 1987 IEEE Particle Accelerator Conference, IEEE Cat. No.87CH2387--9, 1681(1987).[4] R. Tatchyn, A. Toor, J. Hunter, R. Hornady, D. Whelan, G.Westenskow, P. Csonka, T. Cremer, and E. Kdllne, "Generation of Soft X-Ray/VUV Photons with a Hybrid/Bias Micropole Undulator on the LLNL Linac," Journal of X-Ray Science and Technology 1, 79(1989).[5] R. Tatchyn, P. Csonka, and A. Toor, "Perspectives on micropole undulators in synchrotron radiation technology,” Rev. Sci. Instrum. 60(7), 1796(1989).[6] P. Csonka and R. Tatchyn, "Short-Period Undulators for Human Angiography," Proceedings of the Workshop on Fourth \Generation Light Sources, M. Cornacchia and H. Winick, eds., SSRL, Feb. 24-27, 1992, SSRL Report No. 92/02, p.555.[7] D. Boyers, A. Ho, Q. Li, M. Piestrup, M. Rice, and R. Tatchyn, "Tests of variable-band multilayers designed for nvestigating optimal signal-to-noise vs. artifact signal ratios in dual-energy digital subtraction angiography (DDSA) maging systems," Nucl. Instrum. Meth. A 346(3), 565(1994). [SLAC-CRADA-9302][8] R. Tatchyn, T. Cremer, D. Boyers,1 Q. Li,1 M. Piestrup, “Multilayer optics for harmonic control of angiography beamline sources,” Review of Scientific Instruments, Volume 67, Number 9, September 1996. [SLAC-CRADA-9302][9] R. Tatchyn, T. Cremer, P. Csonka, D. Boyers, and M. Piestrup, ”Remarks on the Role of Multilayer Optics and Short Period Insertion Devices for Medical Imaging Sources and Applications,” Medical Applications of Synchrotron Radiation: Proceedings ofthe International Workshop on Medical Applications of Synchrotron Radiation,M. Ando and C. Uyama, eds., , Springer Verlag, Tokyo, 1998. [SLAC-CRADA-9302][10] J.T. Cremer, M.A Piestrup.; H.R. Beguiristain, C.K. Gary, R.H. Pantell, R. Tatchyn, “Cylindrical compound refractive X-ray lenses using plastic substrates;” Review of Scientific Instruments; Sept. 1999; vol.70, no.9, p.3545-8.


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SUMMARY

• molecular imaging and other frontier applications with nm or sub-nm resolution requirements will require LCLS or other ultra- low emittance 4G SR machines, insertion devices, and optics

• high resolution imaging or structural studies of crystals may be well- matched to short period undulators on low energy storage rings - if augmented with suitable optics

• moderate or low-resolution applications such as coronary angiography are likely to benefit strongly from the development of short- period undulator technology, in particular laser-field undulators.

• pulsed-mode operation of machine and insertion device may allow performance parameters and imaging modes unattainable in steady-state operation

• the development of unconventional techniques such as SXI will require corresponding innovations in optical, machine, and insertion device technologies

Documents

R. TatchynIAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 1 Pulsed Laser Undulators Excited by Compact Storage Rings: A Candidate Technology for