Soft Xray Beamline

1
Soft X-ray Beamline

• Hafeez Hoorani
• National Centre for Physics
• Islamabad - PAKISTAN

2
(No Transcript)
3
Relevant spatial and temporal frequency scales
for various physical phenomena
4
Spatial and temporal frequency sensitivities of
various techniques
Coherent scattering
5
Science with SR

• APPLICATIONS
• Nano science (quantum confinement, dynamics of
  self assembly, in-situ studies)
• Strongly Correlated Systems (high Tc
  superconductor, CMR)
• Magnetism (magnetic circular dichroism, exchange
  bias)
• Energy (solar energy, combustion dynamics,
  electrochemical cell, Hydrogen storage)
• Environment (in-situ elemental/chemical
  identification of
• contaminants, imaging)
• Catalysis (tailoring of catalysts, surface
  characterization)
• Medical Science (in-situ imaging, macromolecular
  crystallography)

6
Usage of Soft X-ray BL

• VUV/Soft X-ray covers an energy range from 5 -
  5000 eV
• Can be sub-divided further into two ranges
• Low energy range 5 - 1500 eV
• High energy range 1000 - 5000 eV
• The division is based upon the instruments used
  for studies in two energy ranges

7
Low Energy Range 5 - 1500 eV

• K absorption edges of elements in the first row
  of periodic table
• C (285 eV), N (410 eV), O (545 eV)
• One can study
• Petrochemicals
• Polymers
• Biological systems
• Environmental samples

8
Low Energy Range 5 - 1500 eV

• L absorption edges (2p core 3d valence) of
  magnetic transition metals (cobalt, iron, nickel)
• Use of X-ray Absorption Near Edge Spectroscopy
  (XANES)
• L edges of Si (100 eV), Mg (640 eV), Cu (940 eV)
• Applications are in magnetic storage devices,
  role in computer technology and solar cell.

9
Low Energy Range 5 - 1500 eV

• 10 - 100 eV photons are used for the study of
  valence-band electronic properties
• Techniques
• X-ray Photoelectron Spectroscopy (XPS)
• Electron Spectroscopy for Chemical Analysis
  (ESCA)
• Electrostatic electron energy analyzers

10
High Energy Range 1 - 5 keV

• The range 1 - 5 keV covers the K-edges
• Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti
• Monochromators use crystals
• Beryl 800 - 1500 eV
• Quartz 1400 - 1800 eV
• InSb 1800 - 2000 eV
• Ge (111) or Si (220) 2 - 5 keV

11
Energy scales of various excitations
Soft x-ray resonances (3p --gt 3d) provide a very
sensitive channels of excitations MERLIN (meV
res. beamline Spectrograph 3 meV
12
Nanoscience Electronic Structure Determination -
Techniques of choice

• Need,in situ, investigation of
• Valence orbital (bonding, energy gap)
• Core level (charge transfer, elemental/chemica
  l specificity)
• How?
• Unoccupied bands are studied by Absorption
  Spectroscopy
• Occupied band are studied by
• Emission Spectroscopy and
  Photoelectron Spectroscopy
• Use of polarizations allows to probe the
  orientation of molecules on surfaces

h?
X-Y
X?Y?
Requires close coupling between theory and
experiment
13
Beamline 11.0.2 Schematic
14
Elliptically polarizing undulator
15
Requirements Soft X-ray Beamline _at_ SESAME

• Photon Energy Range 50 to 2000eV
• Resolving Power 10,000 25000 (High
  Resolution and
• moderate resolution with high flux modes)
• Control of linear polarization and circular
  polarization
• KB focus to 5mm vertically for XES
  (spectroscopy)
• Full power, high resolution at 50-100eV for
  high resolution band structure mapping
  (spectroscopy)
• Fully optimized endstation with Scienta electron
  energy analyzer, emission spectrograph and
  sample transfer system
• Roll-up port with pathway for future development
• User friendly (advanced designing but easy in
  use)

16
Soft X-ray Beamline Layout
Minimum (4)of Advanced Optics High
resolution with no translation Of slits or
grating Tank
17
Endstation SESAME

• High Performance
• Scienta analyzer
• Advanced sample
• Manipulator
• UHV sample transfer
• Photodiode

18
Cost of the beamline

• Optics (mirrors and 2 gratings) 600k
• Mirror tanks and controllers 200k
• Monochromator tank and controller 400k
• Vacuum Hardware, stands and pumps etc 400k
• Control system, wireways 200k
• Project management (3months) 60k
• Experimental Station 750k
• Contingency (10) 260k
• Grand Total 2,870k

Undulator and the front end provided by
SESAME Requires training of 3 scientists and 2
engineers _at_ ALS (urgent)
19
Resolution Low Energy Grating (LEG)
5 meV _at_ 100eV
20
Resolution High Energy Grating HEG
20 meV _at_ 500 eV
21
Resolution at 100 eV (LEG)
h? 100eV
Sigmas are for the central ?
22
Resolution at 400 eV (HEG)
h? 400eV
23
Resolution at 1000 eV (HEG)
h? 1000eV
24
Total Resolution (various gratings and slit
settings)
25
Grating efficiencies
26
Total Flux at sample