PSI - Issue 33

Dionysios Linardatos et al. / Procedia Structural Integrity 33 (2021) 304–311 Linardatos / Structural Integrity Procedia 00 (2021) 000 – 000

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4

IC = π ∫ log 2 (1+NEQ(u))udu 0 ∞

(5)

3. Results and Discussion Figure 1 shows the NEQ for the present NDT detector, calculated from its DQE and the measured X-ray photon distribution at the detector surface (Linardatos et al., 2021). The shapes of the NEQ curves are affected by both noise and resolution. The amplitude of NEQ is affected by the number of X-rays at the detector surface (photons/mm 2 ). As is it obvious from Figure 1, the NEQ peaks at the low frequency range, i.e., 0 to 2 cycles/mm. The 48.3 μGy exposure provided higher NEQ values due to the higher number of incident X-rays (photons/mm 2 ). The higher NEQ values at the low spatial frequency range is of interest for general radiography applications.

Fig. 1. Comparison of the NEQ curves for both the examined exposures, under the RQA-5 beam quality.

In Table 1, a comparison is given of the IC values between the CMOS sensor under consideration, with previously published values for a similar CMOS sensor coupled to Gd 2 O 2 S and CsI scintillators (Michail, 2015; Michail et al., 2015; Seferis et al., 2013). The present detector’s IC value refers to the 48.3 μGy exposure, while the comparison was obtained at the closest available exposure level, as published for every screen/sensor combination under the RQA-5 beam quality.

Table 1. IC of various CMOS-scintillator combinations (Michail, 2015; Michail et al., 2011b, 2015; Seferis et al., 2013).

Coating weight (mg/cm 2 )

Information capacity (bits/mm 2 )

CMOS optical sensor Remote RadEye HR (20 μm pixel pitch) Remote RadEye HR (22.5 μm pixel pitch)

Scintillator screen

Gd 2 O 2 S:Tb (Carestream Min-R 2190)

33.91

2119

Gd 2 O 2 S:Pr,Ce,F

35.7 65.1 47.3

1813 1826 2229

Gd 2 O 2 S:Eu

CsI:Tl

As it can be seen from Table 1, the IC value of the CMOS sensor under investigation is higher than that of a similar CMOS coupled to a Gd 2 O 2 S:Eu and a Gd 2 O 2 S:Pr,Ce,F screen. Instead, it was found lower than a CMOS/CsI:Tl combination. These data show that, for a given level of incident X-ray fluence, the information capacity is mainly