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X-ray Photo-Electron Spectroscopy Beamline (BL-14)

X-ray Photo-Electron Spectroscopy Beamline (BL-14)

Introduction:

The X-ray Photo-Electron Spectroscopy (PES) Beamline is devoted to the high-resolution photoelectron spectroscopy of solids in the hard X-ray region. The beamline that has indigenously designed and developed optical components will cover an energy range from 2 keV to 15 keV. It combines the powerful technique of X-ray photoelectron spectroscopy to probe the elemental composition, chemical state and electronic states of elements in near surface region of solids. In this technique, a material is bombarded by high energy X-ray and an energy spectrum of emitted photo-electrons is analyzed. The spectrum is used to calculate binding energy of electrons in the material which that in turn provides information of elements present on the surface and their bonding with other elements. Typically lab based PES provides information on materials up to a depth of about 1 nm due to small mean free path of emitted electrons. The high energy X-ray would provide information at larger depths, as the mean free path increases with electron energy. The synchrotron source provides high intensity X-rays over a wide range of energies and PES at different energies is expected to provide chemical information as a function of depth. The beamline components include a Pt-coated toroidal mirror for focussing the X-ray beam, a Double Crystal Monochromator for wide tuneable X-Ray energy range up to 15 keV, water cooled X-ray slits for defining beam opening and high resolution hemispherical analyzer based experimental station for acquiring PES data. Optical and mechanical layout of the beamline is shown in Fig.1 and Fig.2.



Beamline layout:

Optical Layout
Fig1.: Optical Layout of the PES beamline


Mechanical layout
Fig2.: Mechanical layout of the PES beamline


Beamline Specifications:

Source

Bending magnet

Energy Range

2-15 keV

Pre-Mirror

1.1 m long Pt-coated horizontal toroid mirror with sagittal and meridionalradii of curvatures of 18.0 cm and 2.22 km respectively

Monochromator

Double Crystal Monochromator (DCM) using Si (111) crystal with energy resolution ( ΔE/E) ~ 10-4

Spot size @sample position

400 μm (H) x 400 μm (V)

Photon flux [ph/s]

1010 - 1011

Horizontal divergence

3.0 mrad

Experimental Station:
The experimental station consists of an ultra-high vacuum compatible chamber in which various probes, analyzers, detectors and other facilities are housed. It is made of stainless steel with suitable ports to let the synchrotron radiation in and designed to reach a base pressure ≤ 5x10-9 mbar to provide clean conditions for sample analysis. A high energy (up to 15 keV) hemispherical deflector analyzer capable to provide energy resolution ~ 10-4has been designed and fabricated. For detection of high energy photo electrons from HDA, a high resolution 2D imaging system has been implemented using a MCP (Micro-channel Plate) detector having linear active diameter about 40 mm.

Present Status

The DCM has been tested and monochromatic beam at different wavelengths has been obtained. Testing of other major components of the beamline and alignment has been completed. Optimisation of the hemispherical analyzer and detector system is being carried out presently.

Contact Number : 244 2514

Contact Information:

Dr. S. C. Gadkari

gadkaribarc.gov.in

Technical Physics Division
Bhabha Atomic Research Centre,
Mumbai – 400 085.

Shri  M.R. Singh

mrsinghbarc.gov.in

Dr. Jagannath

ssai(at)barc.gov.in

Shri R. K. Sharma

rajendra(at)barc.gov.in

Shri U. K. Goutam

ukgoutam(at)rrcat.gov.in

Shri Kaushik Dutta

kdutta(at)barc.gov.in


Last Modification on: July 2016