The first Indian electron synchrotron produced radiation from its storage ring, Indus-1, during April 1999. After several commissioning trials, the bending magnet beam ports were made available to various beamline scientists for installation of their beamline. The Inter University consortium for DAE Facilities with University scientists had been given the responsibility of designing and constructing an angel integrated photoelectron spectroscopy beamline on this 450 KeV electron storage ring. A storage ring of this kind is most suitable for investigation in the energy range form a few electron volts to around seven to eight hundred electron volts. We report here the designing construction and commissioning of a photoelectron spectroscopy beamline on Indus-1. The first photoelectron spectrum was recorded on 9^th November 2000 at 8.20 P.M. This beamline is now in operation and open for user community. In this article we give a brief description of the beamline and the photoelectron spectrometer. Then we present some spectra recorded on standard samples as examples of the capability of this beamline. Beamline description

Figure 1 shows a complete assembled beamline along with the experimental station. The beamline is connected to bending magnet port through a front-end section. This section acts as safety device to the storage ring in case of any accidental breakdown of beamline. The main components of front-end section are a fast acting shutter (1-2 ms), a fast acting ultra high vacuum gate valve (1-2 s) and an acoustic delay line.

            The photoelectron spectroscopy beamline is designed to utilize photons in the energy range of 10 to 200eV. The beamline operates at a vacuum better than of 10^-9 Torr. The basic requirements for carrying out photoemission experiments are good photon flux and moderate resolution. Since toroidal grating monochromators (TGM) fulfill these two requirements, the present beamline is developed around it. The optical layout of the beamline, based on a design described earlier is shown in Fig.2.

 Optical components of beamline consist of a pre-mirror to focus the incident radiation, monochromators to select the desired wavelength (energy) and a post mirror to focus the monochromatic beam on the sample. In order to have good reflectivity in this energy range, a grazing incidence reflecting optics is used. A toroidal pre-mirror which kept at a distance 4000 mm form the source accepts radiation over horizontal and vertical acceptance angles of 10 and 2.5 mrad respectively. The grazing angle of incidence at the mirror is about 4.5^o, giving a deviation of 9^o after reflection. The reflected beam is brought to a focus at a distance of 2000 mm where the entrance slit of TGM is located. The pre-mirror section is followed by a TGM (Jobin Yvon-TGM2634) which contains three inter changeable gratings to cover a photon energy range form 10 to 200 eV. Any one of the three gratings can be brought into working position to select the desired energy. Energy scanning is achieved by rotating the grating around its axis passing through its center. Monochromatized beam passing an exit slit falls on post focusing toroidal mirror. This mirror has entrance and exit arm distance of 990mm. The deviation produced by this mirror is 9^o keeping outgoing radiation parallel to incoming beam. This mirror produces a unit magnification.

 

            The mechanical layout of beamline includes various components such as laser alignment box to align the beamline, beam viewers after each optical element to monitor the beam and a photodiode after the post-mirror to measure three incident flux. The mechanical design has three modules, viz. pre-mirror chamber, monochromator and post-mirror chamber. Each module³is separated by ultra high vacuum gate valve. This construction helps in avoiding venting the complete beamline in case of any breakdown. The mechanical design of pre-mirror and post chamber and its holding mechanism is made in such a way that very fine linear, rotary and tilt motions can be imparted to the mirrors under ultra high vacuum conditions for final alignment. A of the order of 1x10^-9 Torr in beamline is obtained by distributed ion and turbo pump combination. Experimental station for the beamline is described

Separately in this activity report

Table 1 gives beamline specifications normally needed to plan experiments for users.

Table1. Beamline specifications