SuperESCA beamline description
Overview
SuperESCA has been the first beamline operating at Elettra since 1993. The beamline has been designed primarily for soft X-ray photoemission experiments on surfaces. In order to achieve high energy resolution keeping at the same time a high photon flux, the light produced by the insertion device is collected, monochromatized and brought to the experimental station following a prefoucusing-monochromator-refocusing scheme.
Beamline layout
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Insertion device
SuperESCA and ESCA Microscopy beamlines share a recently (December 2010) installed insertion device: a linear planar undulator (LPU) from Kyma s.r.l. |
Monochromator
The monochromator of the SuperESCA beamline is a modification of the standard version of the plane grating SX700 monochromator. |
The dispersed radiation is finally focused into the exit slit by an ellipsoidal mirror, oriented vertically in order to reduce the slope error problem arising from its aspherical shape. The exit slit aperture can be varied from 5 to 100 um, giving the possibility to find the optimum compromise between energy resolution and flux for each kind of experiment. |
Experimental station
The SuperESCA end-station is represented in the figure. It basically consists of two Ultra High Vacumm (UHV) chambers separated by a gate valve. Preparation chamber
The top, smaller chamber is designed for sample preparation. A VG sputter gun (ion beam energy 0.1÷3 keV) and a gas line allow for standard cleaning procedures. The chamber is also equipped with a plasma source for, e.g., sample functionalization. Moreover, a number of CF ports is availble for the installation of evaporation systems, giving the possibility to prepare samples as thin-films or supported nanoparticles. Main chamber
The bottom chamber is made of μ-metal for optimum shielding, avoiding in this way the influence of magnetic fields that could distort the experimental results. It is equipped with a 150 mm hemispherical electron energy analyser with variable entrance slit, and a delay line detector developed at Elettra. |
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Sample Environment
ManipulatorsTwo different sample manipulators are available. A modified CTPO (from VG) manipulator with 5 degrees of freedom (xyzΘΦ). Since the rotational movements are motorized this manipulator is generally used for angle resolved measuremetns (XPD). It is equipped with a liquid N2 crysostat and an electron bombardment heating system which allow for a sample temperature range of 120÷1500 K. A transfer system, connected to the top chamber by means of a |
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Acquisition software
The experimental apparatus is controlled via a LabVIEWTM based software, developed by the beamline staff. The program fully controls the instrumentation in the experimental chamber: besides photoemission spectra acquired by the electron energy analyzer, for each data set the software registers also the sample temperature, the pressure in the chamber and a reference current for flux calibration. In case of photoelectron diffraction measurements, the program guarantees |
the synchronization between sample rotations and spectra acquisitions. |
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Branch-line layout
In the branch line a toroidal mirror re-focuses the beam at the center of a sencond experimental station. |
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CoSMoS end-station
The Combined Spectroscopy and Microscopy on Surfaces (CoSMoS) facility, belongs to the National Institute of Materials Physics (NIMP) in Magurele, Romania. CoSMoS is installed on the branch-line of the SuperESCA beamline, within a cooperation agreement between Elettra and NIMP. It is a single set-up from SPECS including: (i) a photoemission chamber equipped with a 150 mm Phoibos electron energy analyzer with spin detection system and standard preparation tools and lab sources (sputter, flood gun, monochromatized Al Kα/Ag Lα (about 2.98 keV), high power UV-lamp, etc.). The sample is supported by a five-axis manipulator (x, y, z, θ, φ) with cooling capabilities down to 80 K and heating up to about 1300 K; (ii) a variable temperature (80-600 K) SPECS Aarhus STM with sample cartridge with heating stage; (iii) a MBE system equipped with the same manipulator of the photoemission chamber, LEED, RHEED, thickness monitor, RGA, 6 evaporation cells, and a RF discharge plasma source. |
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Different transfer arms allow moving samples between the three chambers and a fast-entry-lock is used for inserting samples in UHV from air in a few minutes. About 10-12 samples can be accommodated on different storage facilities of the whole setup, which means that all these samples might be prepared and characterized well in advance and ready for the synchrotron radiation measurements. Once fully operating the CoSMoS facility will be made available also to external users. It will feature the rare requisite to combine synchrotron-based photoemission techniques with STM and an MBE deposition system, all the preparation and measurement operations being performed in situ. |