An overview of Indus-1 beamlines   R V Nandedkar   Synchrotron Utilization Division  

Indus-1 has four bending magnets of field 1.5 Tesla and radius of 1 meter.  Each bending magnet vacuum chamber has two ports at 100and 500.   Beamlines can be drawn from only three bending magnets as the fourth magnet is close to the injection septum magnet.  From these three bending magnets, it is possible to tap six beamlines.  Figure 1 gives the schematic representation of the experimental hall showing various locations of beamlines.  A present three beamlines are operation.  One is commissioned and two more beamlines are in the advanced stage of commissioning and will be operational soon.  The characteristics of these beamlines are given in Table 1.  Using Indus-1 beamlines some research papers have already appeared in various International journals.

Figure 1: Schematic representation of experimental hall Indus-1 along with location of various beamlines.

The reflectivity beamline is designed taking 10 mrad as horizontal and 5 mrad as vertical divergence from bending magnet DP2 of Indus-1. The pre-mirror is a toroidal mirror to focus the SR beam on to the entrance slit of the monochromator with a vertical deflection. The beam is incident at 4.50 to the mirror surface. This mirror is gold coated and has a demagnification ratio of 2:1. The monochromator used in this beamline is a toroidal grating monochromator (TGM) type. The entrance slit of the monochromator can be changed in horizontal direction from 0.4 mm to 3 mm in four discrete steps, whereas the vertical slit is adjustable from 0.0 to 1.8 mm continuously. The deflection angle at the grating is 1620. The three interchangeable gratings (200,600 and 1800 lines/mm) cover the wavelength from 40.A to 1000 A. The average spectral resolution for this wavelength range is 500. The post mirror is also a toroidal type to refocus the monochromatic beam on to the target, which is kept at a distance of 1.8 meters from the center of the mirror. The demagnification ratio is 1:1. The typical spot size is 1 mm (h) x 1 mm (v). The experimental station on this beamline is a multipurpose reflectometer. It operates in the vacuum of 5 x 10-8 mbar and has a two-axis goniometer with independent and coupled rotation of sample and detector with an angular resolution of 2.5 mdeg. In between the beamline and the reflectometer a differential pumping station is installed as the beamline is under vacuum of 10-9 mbar. It is possible to set the reflectometer in either s or p polarization geometry. The detectors that are used are either Si or GaAsP photodiodes.

Table 1: Characteristics of these beamlines on Indus-1 SR facility

Beamline	λ – range	Monochromator	Organisation	Status,
1. Reflectivity	40 – 1000 Å	TGM	CAT, Indore	Operational Nov. 2000
2. Angle integrated PES	60 – 1600 Å	TGM	IUC, Indore	Operational Nov.2000
3. Angle resolved PES	40 – 1000 Å	TGM	BARC, Mumbai	Commissioned in Dec. 2002
4. Photophysics	500 - 2500 Å	Seya-Namoika	BARC, Mumbai	Commissioned in March. 2003
5. High resolution VUV	400 - 2500 Å	Off-plane Eagle	BARC, Mumbai	Construction
6. Photo absorption (PASS)	100 - 700 eV	SX700	BARC, Mumbai	Construction

Angle Integrated PES beamlines is built by the Inter University Consortium, Indore.  This is again a TGM based beamline on bending magnet DP1, with toroidal mirrors as pre and post focusing optics.  The acceptance of the beamline is 10 mrad (h) x 4 mrad (v).  The entrance arm length of the monochromator is 1500 mm and the exit arm length is 2634 mm.  The wavelength that can be covered by three interchangeable gratings is 60 to 1600 A.  The experimental station is an indigenously built angle integrated photoelectron spectrometer.  It comprises of an ultra high vacuum chamber in which a 100 mm radius hemispherical analyzer and a channeltron detector are housed.  The chamber is equipped with sample manipulator with x-y-z motors, sample heating (900⁰ C) and sample cooling (liquid nitrogen temperature) facilities.  The sample preparation chamber has a diamond file to scrub the sample surface and a quick load lock system with a magnetically coupled transfer rod.  The measured resolution of the energy analyzer is 800 meV.

An angle resolved photoelectron spectroscopy beamline is built by Bhabha Atomic Research Centre (BARC), Mumbai on bending magnet DP2.  It is based on a toroidal grating monochromator.  The UHV chamber of the spectrometer contains both angle resolved and angle integrated electron analysers.  The chamber also has a low energy electron diffraction and an Auger probe to determine the orientation of single crystals, a sample manipulator and an argon-ion sputter etch gun for in situ sample cleaning.  Expected resolution of the analyzer is between 50 to 100 meV. 

Photophysics beamline is also built by BARC on the bending of magnet DP3.  The wavelength that can be covered by using a 1 metre Seya-Namioka monochromator with a spherical grating (2400 1/mm, gold coated) is 500 to 2500A.  The beamline acceptance is 41 (h) x 5.6(v).  The experimental station consists of a 250 mm diameter UHV cell for absorption and emission spectroscopy experiments in gas phase and an UHV chamber and a sample holder for solid samples.

In addition, two more beamlines are under fabrication stage.  These are high resolution spectroscopy beamline with a 6.65 metre spectrometer in the off axis eagle mount having gold coated concave grating, and a photo absorption spectroscopy beamline on a plane grating monochromator to study the absorption edges in the energy range 100-70 eV.  These beamlines will take a while before they are set up on Indus-1.

After the shut down of BESSY-I in Berline, Germany, three beamlines were critically evaluated for there installation on Indus-1.  These are - a TGM beamlines, a high-energy TGM and a 1m Seya-Namioka beamline.  BESSY has kindly given these beamlines gratis to India and these beamlines have already been transported to Indore.  For the installation of these and some other beamlines, dipole vacuum chambers of Indus-1 need modification.  The design for the new chambers has been finished and they would be fabricated shortly.

In addition to these beamlines, several offline experimental facilities are also available for users.  These facilities include a laboratory bard x-ray fluorescence (XRF) system, a total external XRF on an x-ray generator, vacuum emission spectrometer, a transmission analytical electron microscope, a scanning electron microscope etc.  A hard x-ray reflectivity set-up on the x-ray generator will be available soon.