1 Generation of quasi-monochromatic soft x-rays using a table-top electron accelerator Alexander Lobko Institute for Nuclear Problems Belarus State University July 2009 X Intl Gomel HEP School

2 Light sources Nanoscience Life sciences

3 Typical size of contemporary synchrotron

4 Budget of the SOLEIL synchrotron Construction Investment…………….235 M€ Operation………………..64 M€ Salaries………………….150 M€ Total………………………….449 M€ Yearly………………………...53 M€

5 Why do we need (quasi)-monochromatic soft x-rays?

6 Soft X-Ray Spectroscopy Methods: Soft x-ray absorption spectroscopy (XAS), near-edge x-ray absorption fine structure (NEXAFS) spectroscopy, soft x-ray emission spectroscopy (SXES), resonant inelastic x-ray scattering (RIXS), x-ray magnetic circular dichroism (XMCD),x-ray photo- emission spectroscopy (XPS), Auger spectroscopy. Problems: Complex materials Magnetic materials Environmental science Catalysis The photon energy tunability and its brilliance for some above listed applications are essential.

7 Soft X-Ray Scattering Methods: Soft x-ray emission spectroscopy (SXES), inelastic x-ray scattering (IXS), resonant x-ray inelastic scattering (RIXS), speckle patterns, small-angle x-ray scattering (SAXS). Problems: Strongly correlated materials Magnetic materials Environmental science Catalysis The tunability of radiation and its brilliance for some above listed applications are essential.

8 Soft X-Ray Imaging Methods: Soft x-ray imaging, photoelectron emission microscopy (PEEM), scanning transmission x-ray microscopy (STXM), full-field microscopy, x-ray diffraction imaging (XDI), x-ray tomography, computer-aided tomography (CAT). Problems: Cell biology Nano-magnetism Environmental science Soft matter, polymers The tunability of radiation is absolutely essential for the creation of contrast mechanisms.

9 Applications to the life sciences Potential to form high spatial resolution images in hydrated bio-material Ability to identify atomic elements by the coincidence between photon energy and atomic resonances of the constituents of organic materials Concern Radiation-induced damage: photon energy deposited per unit mass (dose) can cause observable changes in structure

10 Soft x-ray water window

11 Micro-beam radiotherapy

12 Indirect radiation therapy

13 Monochromatic X ray medical imaging By narrowing x-ray spectrum inside of the range required for a specific medical imaging application, a patient’s radiation-induced damage may be significantly reduced. It has been evaluated that x-ray examinations performed with quasi mono-energetic x-rays (even 15-20%) will deliver a dose to the patient that will be up to 70% less than dose deposited by a conventional x-ray system [P. Baldelli [et al] // Phys. Med. Biol. 49 (2004) 4135].

14 Optimal X-Ray Energies for Medical Imaging mammography keV; radiography of chest, extremities and head keV; abdomen and pelvis radiography keV; digital angiography - ~33 keV.

15 How much monochromatic soft x-ray photons we need?

16 Evaluation of X-Ray Flow for Medical Imaging The Physics of Medical Imaging / S. Webb (Ed.), Bristol: Hilger, x t

17 What do we need for high-quality in vivo imaging? Number of x-ray quanta needed to visualize 1.0 mm 3 of biological tissue at 1% contrast is ~3x10 7 photons/mm 2. This evaluation made for film registration. In case of digital detection 4×10 4 photons per ~0.4 mm 2 detector pixel are required. It leads to the flux of ~10 6 photons/mm 2. Due to heart beat and breathing, above photon flux must be provided within ~1/100 s. Photons must penetrate considerable field of vision.

18 What do we exactly need for high-quality in vivo imaging? We need, for example, 3x10 7 mm -2 * 100x100 mm 2 / s = ~3x10 13 (10 12 ) photons/s with tunable x-ray energy in keV range Mono-chromaticity could be of ~10 -2 for a patient’s dose reduction Radiation background should be low

19 Spectral brilliance of x-ray sources There is large gap between properties of common and high energy accelerator-based x-ray sources

20 Comparison of some x-ray generation processes at accelerators Type of radiationYield, photon/e Е, MeV BR1.2*(-8)500 CBR1.7*(-7) SR1.2*(-5)3 *(+3) TR1.0*(-9)125 RR1.6*(-7)50 PXR1.3*(-5)50 V.G. Baryshevsky, I.D. Feranchuk // NIM 228 (1985) 490

21 Compact x-ray source based on Compton back scattering

22 Parametric x-rays V. Baryshevsky, I. Feranchuk, A. Ulyanenkov Parametric X–ray Radiation in Crystals: Theory, Experiment and Applications // Springer, 2006, 176 p. Condition for the Cherenkov radiation emission

23 Motivation to use PXR it is quasi-monochromatic x-rays x-rays energy can be tuned smoothly by single crystal target rotation it is well directed and polarized x-rays x-rays energy does not depend on energy of incident electrons radiation angle can be as large as 180 arc degrees - it means, one may work at virtually low background Optimal target thickness – µm of light crystal material (diamond, silicone, graphite, LiF, quartz, etc) – weak multiple scattering

24 PXR practical applications Rensselaer Polytechnic Institute, NY, USA Nihon University, Japan

25 Racetrack microtron 70 MeV 2.2*1.8*0.9 м3

26 PXR at MIRROCLE Photon Production Laboratory Japan

27 Table-top storage ring MIRRORCLE-20 Electron energy – 20 MeV Average current – about units of Ampere Due to strong multiple scattering only very thin (up to some tens microns) x-ray production targets can be used to prevent beam destruction Number of BR photons from such thin target will be much lower than come from massive anode of a conventional x-ray tube

28 Evaluations of 33 keV PXR emission from 20 MeV electrons E e = 20 MeV, Si target of L=0.01 cm thickness, 33 KeV x-rays, symmetrical Laue case for (111), (220), and (400). Angles between electron velocity direction and direction to diffraction reflex are ~6.9, 11.2, and 15.9 degrees, respectively. Dia 20 cm at 1.5 m ~7·10 -2 rad Quantum Yield: (111) - 3·10 -6 /e - (220) – 4.5·10 -7 /e - (400) – 1.4·10 -7 /e - In some cases account of CB interference is needed

29 Asymmetric case Angle between electron velocity and input plane normal is equal 55 arc degrees, angle between output plane normal and outgoing radiation is equal 35 arc degrees. Plane thickness was chosen equal to 0,00811 сm to provide electron path in crystal equal to L0=L/cos(55 arc degrees)=0,0141 cm

30 Optimal PXR crystal target - wedge To calculate optimal asymmetric geometries and wedge configurations – dynamical theory required

31 Angular distributions in symmetric and asymmetric cases plus 30 degree wedge Azimuth angle, rad – plane target symmetric geometry 2 – plane target asymmetric geometry 3 – wedge target asymmetric geometry Angular density

32 Soft PXR intensity at M-20 Target Si (111) wedge shaped; Bragg angle = 45 arc degrees; E PXR = 2.8 keV; Absorption length 3.57 µm; Geometry – Symmetric Laue; Wedge thickness 0.01 cm; Wedge angle - 30 degrees; Energy resolution (integration)  /  = ; Intensity of PXR+diffracted TR = ~2  ph/e - ; Intensity of diffracted BR = ~5  ph/e -.

33 Wedge targets prototypes At a moment wedge-shaped targets available of Si (111) and (100) base planes with length 3 through 24 mm (step 3 mm) and maximal thickness 450 or 350 mkm. Angle of the wedge and its material can be customized.

34 PXR reflex integral intensity at M-20 Depending on the beam fraction we can apply for PXR generation, in the ideal integral flux may be as high as ph/e * e/s. It means s -1 X ray photons of monocromaticity with tunable energy

35 M-20 beam shape

36 Conclusions PXR radiation mechanism and table-top accelerator can provide flux needed for contemporary soft x-ray applications in high- quality medical imaging and lowered dose radiation therapy. Problems to be considered: Commissioning of the real beam shape as income for more exact evaluations and production of specific targets Target heating PXR angular distribution X-ray harmonics filtering Application of x-ray optics Targets made of photonic crystals – way to T-rays

37 Minsk Ya. Kolas Sq. 1967

38 Many thanks for your attention