1. Generation and Applications Indus Synchrotrons Utilization Division
Focused X-Ray Beams :
Generation and Applications
G S Lodha
Indus Synchrotrons Utilization Division
RRCAT, Indore
I thank the organizer of this prestigious colloquium series for asking we to give a talk. There is a significant difference in the theme of this talk from the talks delivered earlier as the audience were from my research field or students. Here I am before distinguished experts in very many fields of science and technology and I need to communicate how bright x-ray beams available from Indus-1 and Indus-2 synchrotron sources can be used in their specific realms of research. The objective is to put forward a case for having Indus synchrotrons facilities as a scientific hub for multidisciplinary research. Communicating the strength of x-ray beams to a set of experts, who already are aware of most of the information , is a rather difficult proposition, but I venture to make a modest effort. I may please be excused, if some of the projections are too elementary, but I thought of including these for building up a base for what I want to drive home.
The talk will cover the essential ingredients towards generation of focused x-ray beams and the type of science which can be done using these beam. Then I will give a broad introduction to the Indus synchrotron sources available Raja Rammana Centre for Advanced Technology, Indore and the beamlines available as national facilities. I am glad to share an important milestone at RRCAT, “Indus -1 and Indus-2 synchrotron sources are now available to the users on a round the clock basis, week after week”.
With this introduction, in the next 40 minutes, I take you to journey of introducing the topic of generation of focused x-ray beams of micro m to nm and the type of science on can do using these beams.
Advances in Science, Engineering and Technology Colloquium
TIFR, August 20, 2010

2. X-ray Interaction with Matter
Let me start, by refreshing our knowledge of how x-ray interact with matter. Some of the projected figures are taken from the WEB. I have tried to put the required acknowledgements, but I sincerely apologize if I have missed to this at some places.
source: Spring-8 web site

3. 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.
When Roentgen realized that the high energy beams had no charge, he immediately concluded that these may be high light beams and started experiments towards reflection and refraction. By measuring the transmission of single crystal rock salt and powdered salt, he concluded that multiple scattering was insignificant, implying that refractive index of all materials was very near to unity.
With the significant improvement in technology towards generating brighter x-ray sources and fabrication of optical components, it is now possible to focus beams to <30 nm, with ongoing efforts towards reaching diffraction limited resolution in the x-ray region of the e-m spectrum.

4. 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) … (Au,Pt,W)
Dilemma
smaller f smaller R
more flux larger aperture larger R
Refractive index very near to unity for all materials. Refraction is very small. Further absorption is very high. For soft x-ray/ VUV region, air also becomes absorbing. Experiments needs to be done in windowless UHV mode. Extremely rich region of the em spectrum as K, L, M photo absorption edges lie in this region.

5. 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 …)
The question is “Why one wants to focus x-ray beams to finer and finer spot size?” One wants to see objects with features that cannot be observed in visible light because of diffraction limited resolution constraints. One can do some of the imaging at much higher resolution using electron beams (TEM, SEM…), but significant limitations due to multiple complex scattering processes.

6. General Terminology in X-Ray Optics
Magnification
Numerical Aperture
Resolution
Depth of focus
Astigmatism
Chromatic Aberration
Before I get towards putting the projections of various devices used for focusing x-rays, please permit me to reintroduce a few terminologies which all of you are aware while dealing with visible light optics but looking with a prospective of x-ray beam instead of visible beam.

7. 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
Phase shift along the optical path
For generating x-ray micro/ nano focused beam M~10-2 to 10-4 in synchrotron beamline.
Unlike laser sources, most of the x-ray sources are in-coherent. With bright x-ray sources and devices for generating beams with high monocromaticity, one can now generate x-ray beams with high spatial and temporal coherence. With the quality of beams available, the source can be de-magnified by almost This will further improve significantly with the availability forth generation light sources (free electron x-ray lasers), in advanced stage of development in synchrotron light source laboratories.
Magnification: M=Di/Do

8. Numerical Aperture NA= n Sin θmax NA ~ 0.5 (D/f)
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.
Improvement of light collection power of the x-ray optical elements is one of the major technological challenge. With significant improvement in micro/ nano fabrication technology availability, it is now possible to overcome this constraint to a great extent.

9. Focusing increases the angular spread. Brightness: B= P/ (ΔAs . ΔΩs)
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.
Requirement of high brightness in x-ray region can be meet with third and fourth generation light sources and large numerical aperture by improvement in technology towards fabrication of x-ray optics.

10. 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
For higher diffraction limited resolution one needs to use shorter wavelength.
source: D. Attwood

11. Resolution improves with smaller λ

12. Depth of focus Where  is a spot size
Depth of focus increases with energy and decreases with focal spot size. This parameter becomes important for 2D and 3D imaging, as this depends on the depth from which x-rays are scattered in the sample and reaching the detector for constructing the image.
source: Xradia

13. 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 or
Source
Focus or
For x-ray reflecting optics, many a times, one is forced to use extreme grazing incidence optics, where astigmatism become a major constraint, thus requiring aspheric grazing incidence optics of very large size (~1.5 m) with very low figure errors and rms roughness. SR sources are usually asymmetric in shape, but for many experiments there is a requirement of symmetric x-ray beams. One of the major breakthrough came about by decoupling the merridonal and sagittal focusing elements, the technique first proposed by Krapatric and Benz in 50’s but has now become extremely powerfull for nano focusing reflecting optics with high NA.

14. 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

15. X-ray Micro focussing optics
Reflective optics
Diffractive optics
Refractive optics

16. X-ray Reflectivity: Single and Multilayer
Single Layer
Total external reflection when θ<θc (a few mrad)
c = √2  = λ√Z
Multilayer
Large θ leads to larger acceptance or shorter mirror length.
Spectral bandwidth ~ a few %

17. X-ray Multilayer Optics
Advantages
Layer thicknesses can be tailored
Can be deposited on figured surfaces

18. Reflective optics
Schwarzschild objective
Wolter microscope
Capillary optics
Kirkpatrick-Baez mirrors

19. Schwarzschild objective
Near normal incidence with
multilayer coating (126 eV)
N.A. > 0.1
Imaging microscope
source: F. Cerrina (UW-Madison), J. Underwood (LBNL)

20. Wolter microscope
Use 2 coaxial conical mirrors with hyperbolic and elliptical profile
Imaging microscope
Difficult to polish for the right figures and roughness
Conical optics (hyperbolic and elliptical profile). Parabolic profile can be used under relaxed spot requirements. If spot size requirements are further relaxed, one can use cylindrical approximation SXT planned aboard ASTROSAT.

21. Capillary optics One-bounce capillary
Large working distance (cm)
Compact: may fit into space too
small for K-B
Nearly 100% transmission
N.A. ~ 2-4 mrad (¡Ü 2θc)
Difficult to make submicron spot
Multi- bounce condensing capillary
Easy to make with small
opening (submicron)
Short working distance (100 μm)
Low transmission
Limited acceptance. X-ray beam can be pre focused followed by a capillary reflecting optics for further focusing to micron size.
source: D. Bilderback (Cornell)

22. 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)

23. Diffractive optics Fresnel zone plates (FZP)
Multilayer Laue Lens (MLL)

24. 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 
For phase zone plates, the thickness of the material in the material should be such that it introduces a phase difference of phi, between the blocked and unblocked portion. The resolution is dependent the smallest zone width one can make, with the required aspect ratio. As delta decreases (hard x-rays), deta t increases, thus one needs zone plates with very high aspect ratio. One uses x-ray lithography to fabricate high aspect ratio zone plates required for hard x-ray focusing.

25. Fabrication Fresnel zone plates
E Anderson, A Liddle, W Chao, D Olynick and B Harteneck (LBNL)

26. 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!

27. Multilayer Laue Lens (MLL)
For high aspect ratio
Aspect ratio > 1000 (Δr = 5-10 nm, 10 μm thick) demonstrated
Source : A. Macrander (APS)

28. Refractive optics Compound refractive lens (CRL) f = R/2N
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 m
d 10 m -50 m
Parabolic profile : No spherical aberration
Refractive index in x-ray region slightly less than unity. For focusing x-ray beam, one needs to use concave lens instead of convex lens. As refraction term is very small (10(-6)), R should be small and N should be large (compound refractive lens). For reduction of spherical aberration, parabolic profile required. Modern micro fabrication technology has allowed development of refracting optics for the generation of nano focused hard x-ray beams (Major development efforts at ESRF).
Source : Achen Univ., APL 74, 3924 (1999)

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

30. 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.

31. 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

32. Synchrotron Radiation Spectrum

33. Brightness of synchrotron sources

34. X-ray Sources: Peak Brilliance

35. Synchrotron Radiation(SR) Sources…
America: 18
Asia: 25
Europe: 22
Oceania: 1
IV generation light sources under construction/ planning stage.

36. A Typical Synchrotron Facility

37. A typical Synchrotron source
Creating SR light
7/9/2008
(3) Then they pass into the booster ring accelerated to   c
(4) And are finally transferred into the storage ring
A typical Synchrotron source
With
BM and ID
(1) Electrons are generated here
(2) Initially accelerated in the LINAC

38. Building a Synchrotron Source…
Magnets
RF systems
LCW
Beam physics
Power supplies
Survey and alignment
Health physics
Beam diagnostics
Cryogenics
etc.
UHV
Controls
Fabrication and metrology shop
Chemical Cleaning

39. 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

40. Application of SR

41. Life Science Atomic structure analysis of protein macromolecules
Elucidation of biological functions

42. 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

43. 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

44. 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

45. 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

46. 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

47. Medical Application
Application of high spatial resolution imaging techniques to medical diagnosis of cancers

48. SR Based Research Methods
X-ray Diffraction and Scattering
Spectroscopy and Spectrochemical Analysis
X-ray Imaging
Radiation Effects

49. Indus building complex
7/9/2008
Indus building complex

50. Synchrotron Complex at RRCAT housing Indus-1 and Indus-2

51. Schematic View of Indus Complex
TL-3
TL-1
TL-2
Indus-2, 2.5 GeV SR
Trials to store the beam began in December 2005
Indus-1
(450 MeV, 100 mA)
(Working since 1999)
Booster Synchrotron
(700 MeV)
(Started in 1995)
Microtron
(20 MeV)
(Started in 1992)

52. Indus-1 Storage Ring

53. Schematic representation of experimental hall
Five beamlines have been operational.
Several publications (~50) have resulted from utilization of these beamlines.
X-ray absorption and Infra red spectroscopy beamlines under installation

54. Beamlines operational on Indus-1
Range (nm)
Beamline Optics
λ/ Δλ
Experimental station
Pre and Post mirror
Monochromator
Reflectivity (RRCAT)
4-100
Au coated Toroidal
1.4 m TGM with three gratings
~400
Reflectometer and time of flight mass spectrometer 
Angle Integrated PES (UGC-DAE-CSR)
6-160
Pt coated Toroidal
2.6 m TGM with three gratings
~600
Hemi-spherical analyzer (HSA)
Angle Resolved PES (BARC)
1.4 m TGM with three gratings
Angle resolved HSA electron analyzer
Photo Physics (BARC)
50-250
1 m Seya-Nomioka
~1000
Absorption cell , sample manipulator
High resolution VUV (BARC)
70-200
Au coated cylindrical
6.65 m off plane Eagle mount spectrometer
~70000
High temperature furnace, absorption cell

55. 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

56. Indus-2 beamlines Installed being installed/ under construction
BM Beamlines
BL#
Groups
ADXRD (commissioned)
BL-12
RRCAT
EDXRD (commissioned)
BL-11
BARC
EXAFS (commissioned)
BL- 8
GIMS ( being installed)
Bl-13
SINP
PES (being installed)
BL-14
Under Construction
BM MCD/PES
BL-1
UGC-DAE-CSR
Imaging
BL-4
BARC +
ARPES/PEEM
BL-6
White-beam lithography
BL-7
Scanning EXAFS
BL-9
XRF-microprobe
BL-16
SWAXS
BL-18
Protein Crystallography
BL-21
X-ray diagnostics
BL-23
Visible diagnostics
BL-24
Soft X-ray
BL-26
being installed/
under construction
Installed

57. X-ray Multilayer Deposition Laboratory

58. Reflectivity Beamline Indus-1

59. Normal incidence soft x-ray reflector: Mo/Si multilayer

60. 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

61. Soft & Deep X-ray Lithography (SDXRL) beamline -BL7

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

63. SDXRL beamline – Present Status
Primary slits
Installed beamline inside hutch
X-ray mirrors with manipulators
X-ray Scanner

64. BL16 Beamline Front End Beamline optics KB mirror Pre-DCM section DCM
Indus-2 beamlines
BL16
Beamline Front End
Beamline optics
DCM
Beam transport pipes and vacuum components
Front end
exit
KB mirror
Pre-DCM section

65. X-ray Microprobe beamline
Indus-2 beamlines
X-ray Microprobe beamline
Beamline optics
Post-DCM section
DCM
Optics table
Beam transport pipes and vacuum components

66. 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.

67. All are welcome to Indus SR Facility
Thank you

68. Acknowledgements:

69. X-ray Diffraction and Scattering
Research Methods
Typical Examples of Research Subjects
Macromolecular crystallography ( I-2)
Atomic structure and function of proteins.
X-ray diffraction under extreme conditions (I-2)
Structural phase transition at high pressure / high or low temperature
X-ray powder diffraction
(I-2)
Precise electron distribution in inorganic crystals
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

70. Spectroscopy and Spectrochemical Analysis
Research Methods
Typical Examples of Research Subjects
Photoelectron spectroscopy (I-1)
Electronic structure of advanced materials such as superconductors, magnetic substances, and highly correlated electron systems.
Atomic and molecular spectroscopy (I-1)
Photoionization spectra, photoabsorption spectra and photoelectron spectra of neutral , atoms and simple molecules. Spectra of multicharged ions.
X-ray fluorescence spectroscopy (I-2)
Ultra-trace element analysis. Chemical states of trace elements. Archeological and geological studies.
X-ray absorption fine structure (I-2)
Atomic structure and electronic state around a specific atom in amorphous materials, thin films, catalysts, metal proteins and liquids.
X-ray magnetic circular dichroism (I-2)
Magnetic properties of solids, thin films and surfaces. Orbital 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.

71. X-ray Imaging Research Methods Typical Examples of Research Subjects
Refraction-contrast imaging (I-2)
lmaging of low absorbing specimens.
X-ray fluorescence microscopy (I-2)
Imaging of trace elemental distribution with a 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 microscopy (I-2)
Element-specific surface morphology. Chemical reaction at surface. Magnetic domains.

72. 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.

73. Mo/Si soft x-ray Polarizer multilayer