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The goal of adjustment is to achieve the maximum intensity of the spectral lines with the minimal distortions of
their contours. Due to continuous improvements in spectrometers designs it is advised to perform adjustment according
to manufacturers specifications. Following is the procedure, recommended by us, which helps to retain the original
(manufacturer's) adjustment in the course of frequent primary electron energy changes.
Preserving the adjustment during primary electron energy changes
Changing of Ep in the wide energy range (a necessity in IS) (see note)
frequently causes the deflection of the
primary electron beam due to incomplete axial symmetry of the fields in the electron gun. In order to retain the adjustment,
the allowed deflection from the analyzer’s focus must be substantially smaller than the focus itself and the effective beam
diameter. Therefore, IS requires an arrangement to fix the beam direction, which corresponds to the initial adjustment.
Such an arrangement can be done with a Faradey cup (FC), with a diafragm in its screen, comparable in size with
the effective beam diameter. The FC is mounted on the sample holder, in a way to allow its positioning in the analyzer's
focus. The screen of FC (see note) is electrically connected with the holder and the
FC electrode is guided outside of the chamber by a separate vacuum electrical feedthrough.
Before changing the Ep:
FC screen is grounded;
The FC is positioned by manipulator, so that the primary electron beam is targeted into the screen's diaphragm;
The sample holder is manipulated to reach the maximum of electric current on the FC electrode;
The holder's position is fixed.
After changing the Ep:
The electron beam is focused;
The electron beam is targeted into the diafragm of the FC screen by means of deflection plates electrodes;
By deflecting the beam a maximum current is reached on the FC electrode.
After the above described procedure the adjustment is preserved. Practice has proved that with a stable holder's
construction and current maximum precision up to 2nd - 3rd decimal digit it is possible to perform multiple changes of
Ep without loosing the initial adjustment.
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