User Manual LYNXEYE XE Detector
6-6 DOC-M88-EXX240 V1 – 03.2014
6.3 Detector Trimming and Energy Calibration
Trimming of the discriminators (veto, low and high) is required because the amplification in the two
ASICs for each strip is varying a bit.
Due to the fact that trimming is done by a one-point calibration, the trimming is perfect only for one
photon energy (wavelength), it has to be repeated for each photon energy.
Trimming is stable for a long time and needs not to be repeated routinely.
If the x-ray-tube is changed to a different target material, the trimming has to be repeated or loaded
from a previous configuration with the same target.
Trimming is also different for ‘High Resolution’ and ‘High Count Rate’ modus and for ‘High Gain’ and
‘Low Gain’.
Trimming for ‘veto’, ‘low’ and ‘high’ discriminators must be done for the same ‘Mode’ and ‘Gain’ set-
ting.
6.3.1 Veto Trimming
The Veto threshold is a special electronic circuit which cuts photons with a ‘wrong’ photon energy.
Assuming pure Cu-k-alpha radiation, photons can lose partly its energy, due to charge sharing effects
in the detector. A photon hitting the detectors generates electrons proportional to its energy. If this
photon hits one strip at its border, some charges can be lost to the neighboring strip. The result is two
events of different energies showing up as a low energy ‘tail’ in the Discriminator scan. The ‘Veto’ can
detect and eliminate such photons.
The Veto threshold ranges from 0.51V to 0.0V, step size 0.002V. The smaller the Veto is set, the more
photons are cut, which leads to losses in counts and improvement of energy resolution. The Veto
trimming range is -0.008V to 0.0075V, step size 0.0005V.
1. Open the DETECTOR plugin and select the LYNXEYE_XE and activate the ‘Veto Discriminator’
(Figure 6.7).
To Next Page
Loading...