METRA s.r.o.

How does it work


Organic scintillation portal

Large dimensions plastic scintillators (Dimension of 5 x 50 x 100 cm, Surface of 5000 cm2, Volume of 25 l) of Plastic (PVT or plystyren)) are fully compliant with requirements of UNI Standard. Each detector is protected against surrounding background by a suitable 5 mm thick Pb layer on each side, but for the active one, and is thermally isolated against excessive temperature variations/shocks. The enclosure is compliant with NEMA 4 (IP65), white powder painted; special care has been devoted to the front door design, in order to minimize the thickness and the relevant effects on the detector’s performances. The enclosure supports include suitable vibration dumpers, against possible vibration induced noise.

Inorganic scintillation detektor

NaI(Tl) Scintillation Detector is a high-efficiency scintillation detector featuring NaI(Tl) crystal in a in an aluminum housing, including a photomultiplier tube, an internal magnetic /light shield, a high-voltage power supply (HVPS), stabilization electronics, and preamplifier. NaI(Tl) detectors have a proven record of long term reliability but have peak-shifting issues in changing temperatures. NaI(Tl) detector is LED temperature-stabilized, eliminating the peak-shift problems inherent in scintillation detectors. This makes it suitable for use in non-air-conditioned rooms as well as in field applications. The LED temperature-stabilized probe continuously monitors and adjusts the gain of the detector to ensure consistent performance throughout the entire temperature range. The consistent performance allows users to perform nuclear identification under all typical indoor and outdoor conditions while maintaining the highest confidence in the results obtained by the instrument.

Fully-integrated universal digital MCA

The organic and/or inorganic scintillation detectors may be integrated in combination with fully-integrated universal digital MCA. Signals from portal and inspection detectors are collected by digital multichannel analyzer. This is very unique capability for such kind of monitors. This MCA has very low temperature non-linearity. Universal Digital MCA Tube Base for Scintillation Spectrometry is a high-performance, fully-integrated multi-channel analyzer (MCA) tube base that contains everything needed to support scintillation spectrometry. Designed for both laboratory and field use, this one compact unit contains a high-voltage power supply (HVPS), preamplifier and a full-featured digital MCA.

Whole Spectrum Processing

The Spectrum Discovery Software for gamma analysis includes a set of advanced algorithms based on the Whole Spectrum Processing (WSP). These algorithms provide a complete analysis of gamma ray spectra.

The WSP approach brings a new level of capabilities to Gamma Ray Analysis by increasing the sensitivity of the analysis, improving the spectral parameters, eliminating the need for additional user’s experimental calibration, and/or saving the time, money and labor under preservation of the same analytical quality.

The WSP algorithms are based upon methodology of response operator. The response operator model uses a matrix representation, thus, spectra are put into vectors and operators are represented in matrices.

The response operator matrix is built up by SCFA (Scaling Confirmatory Factor Analysis) methodology for each of used detectors. The standard response operator describes detection processes within the detector and has been calculated from a set of several experimental calibration measurements at different energies. The operator includes full energy and efficiency calibration parameters. Therefore, no additional user’s calibration measurements are needed.

The new system works with high level of safety with various types of detectors (semiconductor HPGe, scintillation NaI(Tl), and plastic scintillation detectors). The system needs no modification and no additional calibration, when changing detector types, only exchanging the appropriate response operator is enough.

The WSP approach improves basic parameters (efficiency and resolution) of spectral analysis more than by one order. This significantly lowers number of false alarms signalized by portal monitors and, furthermore, enables performing detailed nuclide identification (NID) of radiation sources and determination of certain interesting materials and substances such as improvised explosives, for example.


The innovated WSP approach to spectral analysis widens the ASP family (up to now including HPGe and NaI(Tl) portals) with a new member of plastic portals. Although the plastic portals with their large area detection are ideal detection medium for ASP, they had poor spectroscopic properties without WSP. Furthermore, WSP significantly (more than by one order) improves spectroscopic parameters of already existed ASP. The WSP improvement may be seen from a short visual study as follows. In comparison, a radioactive source of 60Co that emits two gamma rays with energies of 1.17 and 1.33 MeV was used.
Plastic scintillation portal
Without WSP
With WSP
GammaEntry Peak to Compton Ratio Energy resolution MDA
Without WSP
< 0.01
> 100 Bq
With WSP
> 100
53 keV (8 %)
1 Bq
NaI(Tl) scintillation portal
Without WSP
With WSP
NAIS-3x5x16 Peak to Compton Ratio Energy resolution MDA
Without WSP
50 keV (7.5 %)
5 Bq
With WSP
> 10 000
3.3 keV (0.5 %)
0.5 Bq
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