Beamline Description

The monitor section


The monitoring of the beam intensity now is routinely done by reading the current from the last Zerodur platinum coated REFO mirror. The current can be read or directly from the mirror or from two +100 V Mo plates placed in front of the mirror. The comparison between the REFO current and the Gold mesh shows that in the soft x-rays we gained about two orders of magnitude in the signal intensity. Moreover, the removal of the mesh improves the quality of the focused beam in particular relation to the diffraction introduced by the mesh in particular in the UltraViolet range.      


The monitor section is placed between the refocusing chamber and the experimental endstation. It's destinated to the monitoring of the light intensity, but it is also equipped with a gold coated mirror for single experiment brenchline (for experiments with E<150 eV). The monitoring of intensity is done mainly by reading the current from a gold mesh placed transversally to the beam (usually measurements are done biasing the mesh at -100V in saturation mode). The current of the mesh can be used also as an absolute intensity monitor, using the calibration law obtained recording it simultaneously with a silicon detector AXUV-100.
In case of low signal, the emission current from the mesh is read by CEM (SJUTS model KBL10RS) placed laterally respect to the mesh. In the Visible-UV range, the monitor section is also equipped with a beam splitter, based on a CaF2 flat window and a silicon detector IRD SXUV-300. This detector can be used also as intensity monitor for the branchline.



Gold mesh parameters
Nominal aperture 0.25 mm
wires/inch 82x82
open area 65%
wire diameter 0.06 mm



This curve shows the calculated ratio between the photon flux and the mesh current. Click here to access numerical values.

Estimated Photon flux for typical values of mesh current


Picture of the monitor section (right view)


Picture of the monitor section (left view) with the branch line


Ultima modifica il Martedì, 23 Febbraio 2021 14:12