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Specifications

The instrument can perform Scanning Time Angle Resolved - Photoemission Electron Microscopy
For the specifications see following pages


Spatial resolution
The microprobe is formed using Schwartzschild objectives with multilayers. Two can be installed in UHV at the same time. We have available 27 eV, 74 eV and 95 eV objectives.

   Flux and line width on the sample  (monochromator slit 100 µm)
 
27 eV 2x1010 photons sec -1 5 meV
74 eV 1.5x1011 photons sec -1 70 meV
95 eV 2x1011 photons sec -1 100 meV

    Long range background

We use mostly 27 eV with less than 1 % Background and 74 eV with less than 25 % background.

   Microprobe size

 

    Focal depth

Because of large (0.2) numeric apertire the focal depth is small. We need to focus with precision of approximately 2 µm.



Temporal resolution
This feature is currently under development. First tests showed that if the pass energy of the analyzer is above 10 V we can attribute from which bunch the photoelectrons originate thereby allowing single bunch (tens of psec) resolution in time resolved exeperiments even in multibunch Elettra mode.

     Bunch structure

The bunch width seen by the detector is approximately 1 nsec depending on analyzer pass energy and lens mode and is due to photoelectron trajectories spread caused by finite slit width of the analyzer, however photoelectrons in the same bunch originate from the sampe in the same time moment within bunch lens resolution (tens of psec).

    Time structure on the detector

On the image detector structure for the electrons filtered in a window 100 ps is shown. X axis is energy, Y axis is angle.
Six bunches arrive contemporarily and the zig-zag structure is caused by  imperfections of the entrance slit of the analyzer (to be impropved).



Angular and Energy resolution

   Energy resolution (currently the analyzer entrance slit size is 500 µm along energy dispersion and 12 mm along angle dispersion)

27 eV photons (5 o 10 meV line width)
Pass Energy (V) Resolution (meV)
5 24
10 47
20 93

74 eV photons
Pass Energy (V) Resolution (meV)
monochromator slit 50 µm
Resolution (meV)
monochromator slit 100 µm
5 50 90
10 65 100
20 102 130

   Angular resolution


Analyzer mode Resolution along angular dispersion Resolution along energy dispersion Angle accepted along angular dispersion
WA ±0.27o ±0.67o ±8o
AP0.75 ±0.13o ±0.33o ±8o
AP1 ±0.1o ±0.25o ±6o
AP1.5 ±0.07o ±0.17o ±4o
AP2 ±0.05o ±0.13o ±3o


Here is information on the beamline constructive performance.
Beamline efficiency as a function of photon energy including all optical components without geometrical losses:

From P. Meglpignano et al. Rev. Sci. Instr. 66, 2125 (1995)

Gratings:
  resoling power flux (normalized to 100 mA ring current)
20-62 eV (grating 1) 3600 at 27 eV (slit 100 µm) 2.4x1012 phot sec -1 at 27 eV
60-155 eV (grating 2) 1500 at 74 eV (slit 50 µm) 7x1012 phot sec -1 at 74 eV
125-310 eV (grating 3) 1000 at 244 eV (slit 100 µm) 4.5x1012 phot sec -1 at 110 eV
Last Updated on Thursday, 08 March 2012 14:49