G S LodhaIndus Synchrotrons Utilization

DivisionRRCAT, Indore

Advances in Science, Engineering and Technology Colloquium TIFR, August 20, 2010

lodha@rrcat.gov.in

Focused X-Ray Beams :Generation and Applications

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 OpticsRefractionPhase shift along the optical path

For generating x-ray micro/ nano focused beam M~10-2 to 10-4 in synchrotron beamline.

Magnification: M=Di/Do

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 divergenceThe 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

Source Focus

or

Synchrotron radiation sources

or

Horizontal and vertical focusing are separated at grazing incidence.

fm = (R Sin θ)/2

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

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 NARefractive Optics : f ~ E2

X-ray Micro focussing optics

Reflective optics

Diffractive optics

Refractive optics

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 %

AdvantagesLayer thicknesses can be tailoredCan be deposited on figured surfaces

X-ray Multilayer Optics

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

Multi- bounce condensing capillary

Easy to make with small opening (submicron) Short working distance (100 μm) Low transmission

Capillary opticsOne-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 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 μmAPS 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)

Phase For a phase shift of

Efficiency of an amplitude ZP with opaque zones ~ 10%

Efficiency of a phase ZP with π-phase shift ~ 40%

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)

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

Small aperture Small focusing strengthStrong absorption E>20keV

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

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

IV generation light sources under construction/ planning stage.

Synchrotron Radiation(SR) Sources…

A Typical Synchrotron Facility

(1) Electrons are generated here

(2) Initially accelerated in the LINAC

(3) Then they pass into the booster ring accelerated to c

(4) And are finally transferred into the storage ring

Creating SR light

A typical Synchrotron source

With

BM and ID

Building a Synchrotron Source…

Synchrotron

Magnets

RF systems

LCWBeam physics

Power suppliesSurvey and alignment

Health physicsBeam diagnostics

Cryogenicsetc.

UHV

Controls

Chemical CleaningFabrication and metrology shop

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 dispersionHigh collimation: Various types of imaging techniques with high spatial resolutionLinear / 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

TL-3

TL-1

TL-2

Indus-2, 2.5 GeV SRTrials 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)

Schematic View of Indus Complex

Indus-1 Storage Ring

X-ray absorption and Infra red spectroscopy beamlines under installation

Five beamlines have been operational. Several publications (~50) have resulted from utilization of these beamlines.

Schematic representation of experimental hall

Beamline Range (nm)

Beamline Optics λ/ Δλ Experimental stationPre 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)

4-100 Pt coated Toroidal 1.4 m TGM with three gratings

~400 Angle resolved HSA electron analyzer

Photo Physics (BARC)

50-250 Au coated Toroidal 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

Beamlines operational on 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

Recent studies using Indus -1

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 RRCATVisible diagnostics BL-24 RRCATSoft X-ray BL-26 RRCAT

Installedbeing installed/under construction

Indus-2 beamlines

X-ray Multilayer Deposition Laboratory

Reflectivity Beamline Indus-1

0 20 40 60 80 100

10-3

10-2

10-1

100

100 110 120 130 140 150 160

0.0

0.2

0.4

0.6

0.8

Ref

lect

ivity

Incidence angle deg

Ref

lect

ivity

Wavelength A

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

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

X-ray calibration: Soft X-ray Telescope

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

MEMS (Micro-Gears, …)

High aspect ratio micro-structures

Ø   Fabrication of Hard x-rays opticsØ   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  

SDXRL beamline - Applications

Zone Plate

Primary slits

X-ray mirrors with manipulators

Installed beamline inside hutch

X-ray Scanner

SDXRL beamline – Present Status

BL16

Beamline Front EndBeamline optics

Pre-DCM section

DCM

Front end exit

Beam transport pipes and vacuum components

KB mirror

X-ray Microprobe beamline

Beamline optics Post-DCM section

Optics table Beam

transport pipes and vacuum components

DCM

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

Acknowledgements:

X-ray Diffraction and ScatteringResearch Methods Typical Examples of Research SubjectsMacromolecular 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

Spectroscopy and Spectrochemical Analysis

Research Methods Typical Examples of Research SubjectsPhotoelectron 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.

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.

Radiation Effects

Research Methods Typical Examples of Research SubjectsMaterial processing (I-2) Soft X-ray CVD. Microfabrication.Radiation biology (I-2) Radiation damage of biological substances.

-10 0 10 20 30 40 50 60 70 801E-4

1E-3

0.01

0.1

1

Refle

ctivit

y

Incidence angle deg

Measured Fit

N=120 layersTop SiO2 20.7A: 6.7A: 2.78e-2Si 72.0A; 7.1; 4.22e-3; 1.94e-3Mo 31.0A; 7.0 ; 7.99e-2; 8.66e-3;SubS 5.0ABeam polarization 80%

wavelength 138A

Mo/Si soft x-ray Polarizer multilayer