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IAC Workshop on Medical and Biological Imaging with Novel X-Ray Beams Pulsed Laser Undulators Excited by Compact Storage Rings: A Candidate Technology for Single-shot Medical Imaging Roman Tatchyn* Stanford Synchrotron Radiation Laboratory Stanford, CA 94305 *Talk based on work and contributions of numerous investigators at SSRL, University of Oregon, BPI, BNL, DESY, KEK, ESRF, KIPT, and elsewhere August 8, 2003 R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 1 1.TERMINOLOGY: SOURCE PHASE SPACE: E-BEAM DISTRIBUTION PARAMETERS P HASE SP ACE DIMENSION DISTRIBUTION MEAN DISTRIBUTION VARIANCE HIGHER DISTRIBUTION MOMENTS x y z px py pz <x> <y> <z> <p x> <p y> <p z> <(x-<x>) 2> <(y-<y>) 2> <(z-<z>) 2> <(p x-<p x>) 2> <(p y-<p y>) 2> <(p z-<p z>) 2> R. Tatchyn P ROBABILITY DENSITY FUNCTION Siingle-electron Radiation Cone Distribution Parameters and Relations: ? ? ? ? ? ? IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 2ps r s rx’ > l/2; 2ps ry s ry’ > l/2; 2p s r s rf /f > l/2 2 Key source parameters: Spectral flux: (photons per second, per 0.1% BW) Brightness*: (photons per unit phase space) For a Gaussian e-beam distribution B N phot / s T 8p 3s Tx s Tx 's Ty s Ty 's Tf / f Here the standard deviations are quadratic concatenations of the e-beam and single-electron radiation-cone standard deviations. T 2 e 2 r 2 ( s ) ( s ) ( s E.g., x x x) (s Tf / f ) 2 4(s eE / E)2 (s rf / f )2 *[photons/s,mm2,mr2,0.1%BW] R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 3 Example: R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 4 Examples: R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 5 (em ittance) (em ittance + acceptance) (em ittance +acceptance) (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? R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 6 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 R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 7 EXAMPLE: Conventional DDSA* imaging WIGGLER *DDSA: Dual-energy Digital Subtraction Angiography R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 8 EXAMPLE: Single-shot DDSA imaging based on a Micropole Undulator (MPU) + low energy storage ring* Synchrotron Radiation Solid State PSD DetectorS Micropole Undulator: Magnets Optics B Computer E Micropole Undulator: Laser/Mcrowave Cavity Reduced-Energy Storage Ring Electronics Dichromatic Beam Electron Beam Display Computer-Controlled Chair *P. Csonka and R. Tatchyn, “Short Period Undulators for Human Angiography,” Proceedings of the Workshop on Fourth Generation Sourcrs, 7-99 M.8503A3 Cornacchia, H. Winick, eds., SLAC, CA, 2/24-27,1992, SSRL 92/02, pp. 5556-564. R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 9 EXAMPLE: An alternative imaging technique (SXI (Paul Csonka)) Imposing novel requirements on optics and the insertion device R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 10 INSERTION DEVICES K0.934 l u [cm ]B0 [T] Kl u 2p * c 4p * c K 2 lu * r(t) sin t , 0, ct sin t lu 16p 2 lu 2p * K 2p* c 4p*c *K 2 * (t) cos t, 0, t 2 cos l 4 l u u 2pc * K 2p *c pc * 2 K 2 4p * c Ý (t) sin t , 0, sin t lu l u 2 lu lu 2 R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 K ~ 1 (undulator) lu K 2 l 2 1 2 2 K 1 (wiggler) 2 2 c [keV] E [GeV]B0 [T] 3 11 Motivation for shorter period insertion devices: 2 2 e 2 6 Ý 2 P Ý (CGS) 3 c Total emitted power (flux): 2 e2 P 3 c For sinusoidal trajectory 4 2 Ý pe r p . 2 2 2e 2 2pKc 2e 2 2pKc 2 1 K / 2 P 3c lu 3c l 2 lu lu K 2 l 2 1 2 2 Effect on Brightness (assume fixed K, fixed l, fixed device length): reduce lu l'u lÕu Energy l u in-band flux Nu Brightness 1 lu (however, must also consider net effect of energy reduction on emittance) R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 12 Spectral flux advantage of a short-period (u1) vs. long-period (u2) undulator 1st u1 1st u2 P P K (1 K / 2) lu2 Lu1 Iu1 K (1 K / 2) I lu1 II Lu2 III I u2 IV 2 u1 2 u2 2 u2 2 u1 • for arbitrary fixed Ku1 ~ Ku2 u1 advantage lu2 /lu1 • certain technologies (for which lu1<< lu2) 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. R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 13 Spectral flux advantage of a short-period undulator vs. a wiggler (assume Ku < 0.75) Pu 3E B L I 2K u Bu Lu I u 2 2 Pw Ew B L I (l[Å]) I Bw II Lw III Iw IV 2 u 2 u u u 2 w w w • 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) R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 14 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. : R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 15 Stanford/KIPT Project* Laser Undulator • features: 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 1) high rep rate laser 2) cavity length = interbunch spacing 3) ultra-high Q mirror cavity *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. R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 16 KIPT X-Ray Generator Parameters: Parameter Values Units Laser Wavelength Laser Pulse Length (FWHM) Peak Laser Pulse Power Laser Repetition Rate Cavity Mirror Reflectance Cavity Damp ing (1/e) Time Cavity Damp ing Time Duty Factor Peak Stored Laser P ulse P ower Average Stored Laser P ulse P ower Laser Beam Waist (FW HM) 10600 0.03 210 10 0.9999 0.00022 80 900 360 100 Å m MW KHz s % MW MW m Laser Beam Rayleigh Length Peak Field Intensity Average Field Intensity Equivalent Average K P arameter 0.03 31 23 0.0023 m Tesla Tesla - 100 196 MeV - Electron Beam Energy Electron Beam Electron Energy Spread (FWHM) Horizontal Emi ttance Vertical Emittance Horizontal beta Vertical beta Horizontal Beam Size (FW HM) 3.5 70 70 0.03 0.025 ~100 % nm-rad nm-rad m m m Vertical Beam Size (FWHM) ~100 m R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 17 KIPT Spectrum Radiation far-field target geometry in normalized angle space R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 18 KIPT Spectrum 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. 1 = 180 keV. The duty factor based on a single 3 cm (FWHM) long electron bunch is ~ 514. R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 19 KIPT Spectrum KIPT Compton backscattering 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.. 1 = 180 keV. The duty factor based on a single 3 cm (FWHM) long electron bunch is ~ 514. R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 20 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. R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 21 EXAMPLE: Flux requirements for single-shot DDSA 1) 2 3) 4) 5) 6) 1000 x 1000 element Position Sensitive Detector (PSD) 100x 100 detector p e ~ 105 photons/pixel/shot (~300 S/N) 98% system (optics/patient/detector) losses ~1% useful source bandwidth 20 ms “single-shot” exposure SOURCE REQUIREMENTS: 1) 2) 3) 4) ~ 5 x 1012 photons/shot ~ 2.5 x 1014 photons/s Laser field ~ 500-1000 T Laser power ~ 1 TW 50 J stored laser pulse energy R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 22 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 R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 23 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 of the 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. R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 24 SUMMARY • molecular imaging and other frontier applications with nm or sub-nm resolution requirements will require LCLS or other ultralow emittance 4G SR machines, insertion devices, and optics • high resolution imaging or structural studies of crystals may be wellmatched 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 shortperiod 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 R. Tatchyn IAC Medical Imaging Workshop Pocatello, Idaho, 8/7-8/03 25