Generation of quasimonochromatic soft xrays using a tabletop electron accelerator

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Generationof quasi-monochromaticsoft x-rays
usinga table-top electron accelerator

• Alexander Lobko

Institute for Nuclear Problems Belarus State
University
July 2009 X Intl Gomel HEP School
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Light sources
Nanoscience Life sciences
http//www.lightsources.org/cms/?pid1000166
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Typical size of contemporary synchrotron
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Budget of the SOLEIL synchrotron

• Construction
• Investment.235 M
• Operation..64 M
• Salaries.150 M
• Total.449 M
• Yearly...53 M

www.synchrotron-soleil.fr
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Why do we need (quasi)-monochromaticsoft x-rays?
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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.

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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.

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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.

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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

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Soft x-ray water window
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Micro-beam radiotherapy
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Indirect radiation therapy
www.mpsd.de/irt
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Monochromatic X ray medical imaging

• By narrowing x-ray spectrum inside of the range
  required for a specific medical imaging
  application, a patients 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.

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Optimal X-Ray Energies forMedical Imaging

• mammography - 17-21 keV
• radiography of chest,
• extremities and head - 40-50 keV
• abdomen and pelvis
• radiography - 50-70 keV
• digital angiography - 33 keV.

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How much monochromatic soft x-ray photons we need?
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Evaluation of X-Ray Flowfor Medical Imaging
The Physics of Medical Imaging / S. Webb (Ed.),
Bristol Hilger, 1978.
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What do we need for high-quality in vivo imaging?

• Number of x-ray quanta needed to visualize
• 1.0 mm3 of biological tissue at 1 contrast is
• 3x107 photons/mm2.
• This evaluation made for film registration.
• In case of digital detection 4104 photons per
  0.4 mm2 detector pixel are required. It leads to
  the flux of
• 106 photons/mm2.
• Due to heart beat and breathing, above photon
  flux must be provided within 1/100 s.
• Photons must penetrate considerable field of
  vision.

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What do we exactly need for high-quality in vivo
imaging?

• We need, for example,
• 3x107 mm-2 100x100 mm2 / 10-2 s
• 3x1013 (1012) photons/s
• with tunable x-ray energy in 10-70 keV range
• Mono-chromaticity could be of 10-2 for a
  patients dose reduction
• Radiation background should be low

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Spectral brilliance of x-ray sources
There is large gap between properties of common
and high energy accelerator-based x-ray sources
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Comparison of some x-ray generation processes at
accelerators
V.G. Baryshevsky, I.D. Feranchuk // NIM 228
(1985) 490
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Compact x-ray source based on Compton back
scattering
http//www.lynceantech.com/sci_tech_cls.html
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Parametric x-rays

Condition for the Cherenkov radiation emission
V. Baryshevsky, I. Feranchuk, A. Ulyanenkov
Parametric Xray Radiation in Crystals Theory,
Experiment and Applications // Springer, 2006,
176 p.
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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 10-50 µm of light
  crystal material (diamond, silicone, graphite,
  LiF, quartz, etc) weak multiple scattering

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PXR practical applications
Nihon University, Japan
Rensselaer Polytechnic Institute, NY, USA
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Racetrack microtron 70 MeV
2.21.80.9 ?3
http//nuclphys.sinp.msu.ru/nuc_techn/el_ac/index.
html
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PXR at MIRROCLE
Photon Production Laboratory Japan
www.photon-production.co.jp
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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

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Evaluations of 33 keV PXR emissionfrom 20 MeV
electrons
Dia 20 cm at 1.5 m 710-2 rad Quantum
Yield (111) - 310-6 /e- (220) 4.510-7
/e- (400) 1.410-7 /e-
In some cases account of CB interference is needed
Ee 20 MeV, Si target of L0.01 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.
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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 ?m to provide electron path in
crystal equal to L0L/cos(55 arc degrees)0,0141
cm
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Optimal PXR crystal target - wedge
To calculate optimal asymmetric geometries and
wedge configurations dynamical theory required
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Angular distributions in symmetric and asymmetric
cases plus 30 degree wedge
1 plane target symmetric geometry 2 plane
target asymmetric geometry 3 wedge target
asymmetric geometry
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Angular density
2
1
Azimuth angle, rad
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Soft PXR intensity at M-20

• Target Si (111) wedge shaped
• Bragg angle 45 arc degrees EPXR 2.8 keV
• Absorption length 3.57 µm
• Geometry Symmetric Laue
• Wedge thickness 0.01 cm
• Wedge angle - 30 degrees
• Energy resolution (integration) ??/? 10-3
• Intensity of PXRdiffracted TR 2?10-6 ph/e-
• Intensity of diffracted BR 5?10-6 ph/e-.

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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.
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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
• 10-5 ph/e 1019 e/s.
• It means 1014 s-1 X ray photons
• of 10-3 monocromaticity
• with tunable energy

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M-20 beam shape
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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
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Minsk Ya. Kolas Sq. 1967
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Many thanks for your attention