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What is Synchrotron Radiation

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					               Focused X-Ray Beams :
             Generation and Applications




                     Advances in Science, Engineering and Technology Colloquium



lodha@rrcat.gov.in
X-ray Interaction with Matter




                         source: Spring-8 web site
           Focused X-ray Beams
 W.C. Roentgen : Refractive index of all materials ≈ unity



              Difficult to make an x-ray lens.

With the recent availability of extremely bright x-ray sources
(synchrotron storage rings, x-ray free electron lasers, …),
R&D efforts towards focusing x-rays to smaller and smaller
size have become intense.

At present it is possible to generate focused x-ray beam of
<30 nm, using the reflection, diffraction and refraction
phenomena in the x-ray region.
              Optics for X-ray (~10 keV)
 Complex refractive index: n=1-δ+iβ
 Refraction is small: Re(n)=1-δ with δ=10-6 ….10-5
 Focal length: f=R/2 (n-1) = R/2δ
 Absorption is high: absorption lengths 1μm … 10μm
 Figure of merit: β/δ = 10-5 (Li,Be) …10-3 (C,Al,Si) …10-1
  (Au,Pt,W)
                           Dilemma
 smaller f          smaller R
 more flux           larger aperture       larger R
Why focus x-ray to sub micron size?

 X-ray microscopy: Most materials are heterogeneous at
length scale of micron to nm (transmission microscopy,
scanning microscopy…).

 Increased flux: Higher sensitivity due to reduced
background.

 Small samples or samples in different environment
(pressure, temperature, magnetic field …)
    General Terminology in X-Ray Optics


   Magnification
   Numerical Aperture
   Resolution
   Depth of focus
   Astigmatism
   Chromatic Aberration
Ideal focusing lens: Converts plane wave
       to a spherical wave, with the
      conservation of the coherence
 In-coherent source
  Geometric Optics
   Refraction
      1/F = (n-1) (1/Do + 1/Di)
 Coherent source
  Wave Optics
       Refraction
       Phase shift along the optical path

 Magnification: M=Di/Do
For generating x-ray micro/ nano focused beam M~10-2 to 10-4 in
  synchrotron beamline.
              Numerical Aperture
• Measure of light collection power



NA= n Sin θmax
NA ~ 0.5 (D/f)

  NA is very closely related to performance of the
  optics (e.g. depth of focus, diffraction limited
  resolution, flux etc.). Low NA is one of the
  major constraint for x-ray optics.
    For high photon flux at the focus:
   High brightness and large numerical
                aperture
 Focusing increases the angular spread.
 Brightness: B= P/ (ΔAs . ΔΩs)
P : radiated power; ΔAs :source area ;
ΔΩs : source divergence
The photon flux at the focus is ~ B. 2 . NA2. η
  is spot size and η is the efficiency of the optics.
  Thus the high photon flux at the focus requires
  high source brightness and large numerical
  aperture optics.
 Rayleigh’s Criterion: Resolution Limit




   Point sources are spatially coherent
   Mutally incoherent
   Intensities add
   Rayleigh criterion (26.5% dip)

Conclusion : With spatially coherent illumination, objects are “just resolavable” when

                                                                  source: D. Attwood
Resolution improves with smaller λ
                   Depth of focus




Where  is a spot size




                                    source: Xradia
                      Astigmatism

Horizontal and vertical focusing
are separated at grazing incidence.

fm = (R Sin θ)/2

fs = R/(2Sinθ)              Reflection Crossed mirror pair (Kirkpatrick-Baez system)

                              Synchrotron radiation sources
Source       Focus

                                         or


                 or
         Chromatic aberration




Reflective Optics: Can focus pink beams using
grazing incidence optics. Grazing angles can be
higher by using x-ray multilayer reflector, but
at the cost of limited energy
Diffractive Optics : f ~ E , small NA
Refractive Optics : f ~ E2
    X-ray Micro focussing optics



 Reflective optics

 Diffractive optics

 Refractive optics
X-ray Reflectivity: Single and Multilayer




Single Layer                Multilayer

Total external reflection   Large θ leads to larger acceptance
when θ<θc (a few mrad)      or shorter mirror length.

c = √2  = λ√Z             Spectral bandwidth ~ a few %
X-ray Multilayer Optics




 Advantages
 Layer   thicknesses can be tailored
 Can   be deposited on figured surfaces
           Reflective optics


 Schwarzschild objective

 Wolter microscope

 Capillary optics

 Kirkpatrick-Baez mirrors
               Schwarzschild objective




 Near normal incidence with
  multilayer coating (126 eV)

 N.A. > 0.1

 Imaging microscope




                                source: F. Cerrina (UW-Madison), J. Underwood (LBNL)
                 Wolter microscope


 Use 2 coaxial conical
mirrors with hyperbolic and
elliptical profile

 Imaging microscope

 Difficult to polish for the
right figures and roughness
                     Capillary optics
One-bounce capillary                 Multi- bounce condensing
                                     capillary




 Large working distance (cm)         Easy to make with small
                                       opening (submicron)
 Compact: may fit into space too
                                      Short working distance (100 μm)
 small for K-B
                                      Low transmission
 Nearly 100% transmission
 N.A. ~ 2-4 mrad (¡Ü 2θc)
 Difficult to make submicron spot
                                                      source: D. Bilderback (Cornell)
           Kirkpatrick-Baez mirrors



A horizontal and a vertical mirror arranged to have a
common focus
 Achromatic: can focus pink beam (but not with
multilayer coating)
Can be used to produce ~ round focal spot
 Very popular for focusing in the 1-10 μm
APS 85x90 nm2 ESRF 45 nm, Spring8 25x30 nm2
 (diffraction limit ~ 17 nm)
         Diffractive optics



 Fresnel zone plates (FZP)

 Multilayer Laue Lens (MLL)
          Fresnel zone plates
      (Phase ZP and Amplitude ZP)
 Efficiency of an amplitude ZP with opaque zones ~ 10%

 Efficiency of a phase ZP with π-phase shift ~ 40%
                  Phase               For a phase shift of 
Fabrication Fresnel zone plates




               E Anderson, A Liddle, W Chao, D Olynick and B Harteneck (LBNL)
            Hard X-ray ZP: recently available




                                                  W. Yun (Xradia)



                  Δr = 24 nm, 300 nm thick, Aspect Ratio = 12.5 (Xradia)



Aspect ratio > 100 is probably difficult to achieve with lithographic zone plates!
        Multilayer Laue Lens (MLL)
For high aspect ratio




Aspect ratio > 1000 (Δr = 5-10 nm, 10 μm thick) demonstrated



                                               Source : A. Macrander (APS)
                          Refractive optics

 Compound refractive lens (CRL)
  Small aperture
  Small focusing strength
  Strong absorption E>20keV

  f = R/2N
  R radius (~200 m)
  N number of lenses (10 …300)
   real part of refractive index (10-5 to 10-6)
  2R0  800 m -1000 m
  d 10 m -50 m

  Parabolic profile : No spherical aberration
                                                    Source : Achen Univ., APL 74, 3924 (1999)
      What is Synchrotron Radiation?

Synchrotron radiation is emitted from an electron
traveling at almost the speed of light (0.99999999C) and
its path is bent by a magnetic field. It was first observed
in a synchrotron in 1947. Thus the name

                 "synchrotron radiation".
Generation of Synchrotron Radiation

Synchrotron radiation is emitted at a bending magnet
or at an insertion device. Corresponding to the weak
and strong magnetic field, there are two types of
insertion devices: an undulator and a wiggler.
           General Properties of
           Synchrotron Radiation
 Ultra-bright
 Highly directional
 Spectrally continuous (Bending Magnet /Wiggler)
  or quasi-monochromatic (Undulator)
 Linearly or circularly polarized
 Pulsed with controlled intervals
 Temporally and spatially stable
Synchrotron Radiation Spectrum
Brightness of synchrotron sources
X-ray Sources: Peak Brilliance
      Synchrotron Radiation(SR) Sources…




                        America:      18
                        Asia:         25
                        Europe:       22
                        Oceania:      1

IV generation light sources under construction/ planning stage.
A Typical Synchrotron Facility
              Creating SR light
(3) Then they pass                (4) And are finally
into the booster ring             transferred into
accelerated to   c              the storage ring




                               (1) Electrons are             A typical
                               generated here
                                                        Synchrotron source
(2) Initially accelerated in the LINAC                         With
                                                            BM and ID
  Building a Synchrotron Source…



                             Magnets
            Beam physics                LCW
                               UHV
Survey and alignment                      Power supplies
 Controls                 Synchrotron
                                          Health physics
    Beam diagnostics
                             RF systems   Fabrication and
      Chemical Cleaning
                                          metrology shop
                           Cryogenics
                               etc.
Utilization of the properties of the SR
         beam: A few examples

Microbeam: Diffractometry, microscopy
Pulsed Structure : Time-resolved experiments
Energy Tunability: Crystal structure analysis, anomalous
dispersion
High collimation: Various types of imaging techniques with high
spatial resolution
Linear / circular polarizion : Magnetic properties of materials.
High energy X-ray: High-Q experiments, Compton scattering,
Excitation of high-Z atoms
 High spatial coherence: X-ray phase optics and X-ray
interferometry
Application of SR
                     Life Science



 Atomic structure analysis of protein macromolecules

   Elucidation of biological functions
                Materials Science

 Precise electron distribution in inorganic crystals

 Structural phase transition

 Atomic and electronic structure of advanced materials
  superconductors, highly correlated electron systems
  and magnetic substances

 Local atomic structure of amorphous solids, liquids
  and melts
               Chemical Science

 Dynamic behaviors of catalytic reactions

 X-ray photochemical process at surface

 Atomic and molecular spectroscopy

 Analysis of ultra-trace elements and their chemical
  states

 Archeological studies
         Earth and Planetary Science



 In situ X-ray observation of phase transformation of
  earth materials at high pressure and high temperature

 Mechanism of earthquakes

 Structure of meteorites and interplanetary dusts
             Environmental Science


 Analysis of toxic heavy atoms contained in bio-
  materials

    Development of novel catalysts for purifying
    pollutants in exhaust gases

 Development of high quality batteries and hydrogen
  storage alloys
             Industrial Application

 Characterization of microelectronic devices and
  nanometer-scale quantum devices

 Analysis of chemical composition and chemical state
  of trace elements

 X-ray imaging of materials

 Residual stress analysis of industrial products

 Pharmaceutical drug design
            Medical Application

 Application of high spatial resolution imaging
  techniques to medical diagnosis of cancers
        SR Based Research Methods



 X-ray Diffraction and Scattering

 Spectroscopy and Spectrochemical Analysis

 X-ray Imaging

 Radiation Effects
Indus building complex
Synchrotron Complex at RRCAT
 housing Indus-1 and Indus-2
Schematic View of Indus Complex
                                                           Booster Synchrotron
                                                               (700 MeV)
                                                              TL-1 in 1995)
                                                             (Started
                                         Microtron
                                        (20 MeV)
                                      (Started in 1992)
                                                            TL-2

                                     TL-3
                                                          Indus-1
                                                     (450 MeV, 100 mA)
                                                      (Working since 1999)
   Indus-2, 2.5 GeV SR
 Trials to store the beam began in
           December 2005
Indus-1 Storage Ring
Schematic representation of
    experimental hall

                         Five beamlines have
                         been operational.
                         Several publications
                         (~50) have resulted
                         from utilization of these
                         beamlines.
       Beamlines operational on Indus-1

Beamline          Range                 Beamline Optics                λ/Δλ      Experimental station
                  (nm)     Pre and Post mirror      Monochromator

Reflectivity      4-100    Au coated Toroidal      1.4 m TGM with      ~400     Reflectometer and time
(RRCAT)                                            three gratings               of flight mass
                                                                                spectrometer
Angle             6-160    Pt coated Toroidal      2.6 m TGM with      ~600     Hemi-spherical analyzer
Integrated PES                                     three gratings               (HSA)
(UGC-DAE-
CSR)
Angle Resolved    4-100    Pt coated Toroidal      1.4 m TGM with      ~400     Angle resolved HSA
PES (BARC)                                         three gratings               electron analyzer
Photo Physics     50-250   Au coated Toroidal      1 m Seya-Nomioka   ~1000     Absorption cell , sample
(BARC)                                                                          manipulator
High resolution   70-200   Au coated cylindrical   6.65 m off plane   ~70000 High temperature
VUV (BARC)                                         Eagle mount               furnace, absorption cell
                                                   spectrometer
    Recent studies using Indus -1

 Reflectivity near absorption edge energies
 Hydrogen bond braking near absorption edge
  energies
 Interface studies
 Photo dissociation spectroscopy
 X-ray multilayer optics and optical response in soft
  x-ray region
 X-ray Telescope Calibration
                     Indus-2 beamlines
                                              BM Beamlines           BL#     Groups
                                      ADXRD         (commissioned)   BL-12   RRCAT
                                      EDXRD     (commissioned)       BL-11   BARC
                                      EXAFS        (commissioned)    BL- 8   BARC
                                      GIMS ( being installed)        Bl-13   SINP

                                      PES (being installed)          BL-14   BARC
                                      Under Construction
                                      BM MCD/PES                     BL-1    UGC-DAE-CSR
                                      Imaging                        BL-4    BARC +
                                                                             UGC-DAE-CSR
                                      ARPES/PEEM                     BL-6    BARC
                                      White-beam lithography         BL-7    RRCAT
                                      Scanning EXAFS                 BL-9    BARC
                                      XRF-microprobe                 BL-16   RRCAT
                                      SWAXS                          BL-18   BARC
                                      Protein Crystallography        BL-21   BARC
                                      X-ray diagnostics              BL-23   RRCAT
                                      Visible diagnostics            BL-24   RRCAT
being installed/          Installed   Soft X-ray                     BL-26   RRCAT

under construction
X-ray Multilayer Deposition Laboratory
Reflectivity Beamline Indus-1
Normal incidence soft x-ray reflector:
          Mo/Si multilayer
                                            0.8
                     0
                10
                                            0.6




                             Reflectivity
                                            0.4

                                            0.2
                 -1
            10                              0.0
 Reflectivity




                                              100   110   120   130   140   150   160
                                                          Wavelength A


                 -2
            10




                 -3
            10




                         0                   20                 40                60    80   100
                                                    Incidence angle deg
   X-ray calibration: Soft X-ray Telescope
ASTROSAT :One of the
most ambitious space
astronomy programme
initiated by Space Science
Community in India.
Payload of soft x-ray
imaging telescope (SXT)
sensitive to 0.3 to 8 keV is
planned.
Performance of SXT
grazing incidence foil
mirrors evaluated using
Indus-1 soft x-ray
reflectivity beamline          Archana et al Experimental Astronomy
                               (2010) 28:11-23
Soft & Deep X-ray Lithography (SDXRL)
            beamline -BL7
          SDXRL beamline - Applications




MEMS (Micro-Gears, …)                            Zone Plate
                                 Fabrication of Hard x-rays optics
                                 Small periodicity gratings
                                Micro Electro Mechanical Systems (MEMS)
                                 Photonic band gap crystals (for visible radiation)
                                 Quantum wires and quantum dots devices (high
                                density pattering over large areas)
                                 Fabrication of high density hetrostructures for nano
                                devices
High aspect ratio micro-structures
   SDXRL beamline – Present Status




Installed beamline inside hutch      Primary slits




   X-ray mirrors with manipulators     X-ray
BL16
Beamline Front End
                     Beamline optics


                     DCM




                       Beam transport     Front end
                       pipes and vacuum   exit
                       components


     KB mirror        Pre-DCM section
X-ray Microprobe beamline
Beamline optics         Post-DCM section
                       DC
                       M




                       Beam
                       transport
                       pipes and
                       vacuum
                       components
Road Ahead….
• A modest start has been done at RRCAT with the
  availability of synchrotron radiation sources Indus-
  1 and Indus-2. These sources are being operated on
  a round the clock basis, week after week.
• Few x-ray beamlines have become operational, with
  many more in implementation stage.
• These are national science facilities. Users from
  various fields are welcome to plan research using
  these facilities, which will significantly help us to
  improve the performance further. It will be our
  endeavor to support all users of this national
  facility.
All are welcome to Indus SR Facility




                                       67
Acknowledgements:
           X-ray Diffraction and Scattering
Research Methods               Typical Examples of Research Subjects
Macromolecular                 Atomic structure and function of proteins.
crystallography ( I-2)
X-ray diffraction under        Structural phase transition at high pressure / high
extreme conditions (I-2)       or low temperature
X-ray powder diffraction       Precise electron distribution in inorganic crystals
(I-2)
Surface diffraction (I-2)      Atomic structure of surfaces and interfaces. Phase
                               transition, melting, roughening, morphology and
                               catalytic reactions on surfaces
Small angle scattering (I-2)   Shape of protein molecules and biopolymers.
                               Dynamics of muscle fibers
X-ray magnetic scattering      Magnetic structure. Bulk and surface magnetic
                               properties
X-ray Optics                   X-ray interferometry. Coherent X-ray optics. X-
                               ray quantum optics
        Spectroscopy and Spectrochemical
                    Analysis
Research Methods              Typical Examples of Research Subjects
Photoelectron spectroscopy    Electronic structure of advanced materials such as
(I-1)                         superconductors, magnetic substances, and highly correlated
                              electron systems.
Atomic and molecular          Photoionization spectra, photoabsorption spectra and
spectroscopy (I-1)            photoelectron spectra of neutral , atoms and simple molecules.
                              Spectra of multicharged ions.
X-ray fluorescence            Ultra-trace element analysis. Chemical states of trace elements.
spectroscopy (I-2)            Archeological and geological studies.
X-ray absorption fine         Atomic structure and electronic state around a specific atom in
structure (I-2)               amorphous materials, thin films, catalysts, metal proteins and
                              liquids.
X-ray magnetic circular       Magnetic properties of solids, thin films and surfaces. Orbital
dichroism (I-2)               and spin magnetic moments.
Infrared spectroscopy (I-2)   Infrared microspectroscopy. Infrared reflection and absorption
                              spectroscopy.
X-ray inelastic scattering    Electronic excitation. Electron correlations in the ground state.
                              Phonon excitation.
                         X-ray Imaging

Research Methods         Typical Examples of Research Subjects
Refraction-contrast      lmaging of low absorbing specimens.
imaging (I-2)
X-ray fluorescence       Imaging of trace elemental distribution with a
microscopy (I-2)         scanning X-ray microprobe.
X-ray microscopy (I-2)   Imaging of materials by magnifying with
                         microfocusing elements.
X-ray topography (I-2)   Static and dynamic processes of crystal growth,
                         phase transition and plastic deformation in crystals.
                         Crystal lattice imperfections.

Photoelectron emission   Element-specific surface morphology. Chemical
microscopy (I-2)         reaction at surface. Magnetic domains.
                          Radiation Effects

Research Methods            Typical Examples of Research Subjects
Material processing (I-2)   Soft X-ray CVD. Microfabrication.
Radiation biology (I-2)     Radiation damage of biological substances.
Mo/Si soft x-ray Polarizer multilayer

                 1
                                                                 N=120 layers
                                                                 Top SiO2 20.7A: 6.7A: 2.78e-2
                                                                 Si      72.0A; 7.1; 4.22e-3; 1.94e-3
                                                                 Mo       31.0A; 7.0 ; 7.99e-2; 8.66e-3;
                0.1                                              SubS      5.0A
                                                                 Beam polarization 80%
Reflectivity




                                                                 wavelength 138A
               0.01




               1E-3

                                Measured
                                Fit
               1E-4
                      -10   0   10    20      30     40    50       60      70     80
                                           Incidence angle deg

				
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