The COMPACT.DUO spectrometer measuring head without optics is the classical XRF configuration, equipped however with two X-ray tubes to improve the elemental detection. The fluorescence excitation of the sample is carried out under an angle to the detector in each case.
In accordance with the requirements of the particular task, detectors of different operating principles (such as SDD, Si-PIN and CdTe), air or water cooling for the X-ray tube and a laser range finder (to determine the current distance between sample and detector) can be assembled. Additionally, the measuring head is equipped with an electromagnetic shutter and electrical interlocks preventing radiation hazards.
The local resolution of the X-radiation on the sample is 5-10mm depending on the used aperture diaphragm. For measurements at chalcopyrite solar cells using an SD- detector measuring periods ≥ 5s can be reached. The used X-ray tube in metal-ceramic design (max. 30W, depending on anode material, 50 micron anode spot) is available with different anode materials. The scope of delivery covers, for example, supply and signal processing devices (each with 19'' enclosure for X-ray source or SDD) and a industrial computer including XRF- and control software.
With an acquisition time of 5s an absolute accuracy < 5% and a statistical accuracy of 3% is achieved at present.
Inherent part of the optical layout is the observation of the exciting X-radiation intensity (monitoring). The monitoring is done by exciting of selected materials (markers) matched to the sample material to be measured and arranged in the primary radiation path. For each measurement, the integral intensities of all elements to be detected are normalized to the marker layer intensities. Thus for example, variations of the primary intensity can be compensated which can be caused by warming up the X-ray source to the thermal balance in the respective installation situation or slightest current fluctuations.
The COMPACT.DUO measuring head can be used directly both in the production line (in-line application, ex-situ and off-line in R&D or quality assurance. For the off-line application and large photovoltaic substrates often a combination with the portable scanner ELBRUS iXSCAN.PORT is advantageous.