3.2.1. Room Temperature

The detector was irradiated with a 397 kBq 241Am source placed at a few cm from the detector surface. Figure 9a shows a 241Am spectrum acquired using a SiC microstrip detector at 21 ◦C. The spectrum was acquired at 200 V reverse-bias condition using 12.8 μs peaking time in the triangular signal processing. The pulser line width is 214 eV full width at half maximum (FWHM) corresponding to an equivalent noise charge of 11.6 electrons root mean square (rms). Figure 9b shows a detail of the same measurement up to 28 keV. Several X-ray lines from Mn, Cu, Np, and Ag can be clearly distinguished with a very good resolution, i.e., enough to separate the *K* and *L* lines of neighboring elements. Conventionally, the energy resolution, that is the FWHM, is specified for the Mn *K*α peak at 5.9 keV, which is 213 eV for our SiC microstrip detector at room temperature (Figure 9). It is notable that Si(Li) and silicon drift detectors can achieve 130–150 eV FWHM, and Ge detectors can even achieve 115 eV FWHM for the Mn *K*α peak at 5.9 keV, but with liquid-nitrogen cooling [29].

**Figure 9.** (**a**) X-ray spectrum from a 241Am source acquired at 21 ◦C using the SiC microstrip detector SM1 and an ultra-low noise front-end (PRE5 no. 3); (**b**) detailed X-ray spectroscopy in the energy range 0 to 28 keV.

The analysis of linearity calculated on seven well-resolved peak lines at 8.0, 11.87, 13.94, 17.8, 20.8, 26.35 and 59.54 keV is shown in Figure 10. The percentage error from linearity is below ±0.05%.

**Figure 10.** Analysis of linearity calculated on seven well-resolved peak lines, as shown in Figure 9. The percentage error from linearity is below ±0.05%.

#### 3.2.2. Dependence of X-Ray Response on Detector Bias

The dependence of X-ray response on detector voltage was explored by biasing the detector from 10 V to 200 V at 25 ◦C and using a peaking time of 12.8 μs. A comparison between two spectra acquired at 10 V (bottom, blue) and 200 V (top, red) is shown in Figure 11. The pulser centroid is stable at both 10 V and 200 V. The peak at 13.94 keV shows a small shift of six channels (from 669 at 10 V to 675 at 200 V) which corresponds to 124 eV (Figure 12). The two peaks, as compared in Figure 12a, show a Gaussian symmetry without any tails. This experiment shows that SiC detectors can be operated in a wide range of bias voltages without suffering from a strong performance loss. Figure 12b shows the detection rate of the 13.94 keV photon peak at six different applied reverse-bias voltages, *Vb*. As expected, the photon rate increases with the square root of *Vb* due to the widening of the active region (depletion layer).

**Figure 11.** X-ray spectra from a 241Am source acquired at 25 ◦C and at 10 V (bottom) and 200 V (top).

**Figure 12.** (**a**) Comparison between the two peaks at 13.94 eV obtained at 10 V and 200 V of applied voltage. The Gaussian symmetry without tails can be noticed; (**b**) Detected 13.94 keV photon rate as a function of the applied reverse bias.

#### 3.2.3. High Statistics and Temperature Dependence

Figure 13 shows the results obtained by acquiring an X-γ-ray spectrum for 10 h at 80 V reverse-bias condition, and maintaining the thermostatic chamber at a constant temperature of 30 ◦C. Figure 13a compares spectra acquired after almost 2 h and after 10 h. The very small broadening of the pulser and emission lines should be noted, which demonstrates very good stability of the detector response to X-ray exposure. The analysis of linearity on *K* Cu and *L* Np X-ray monoenergetic lines shows a very small linearity error within ±0.04% after 10 h of acquisition (Figure 13b).

Figure 14 shows a comparison between X-ray spectra acquired at three different temperatures, i.e., −20 ◦C, +30 ◦C, and +80 ◦C. As expected, the width of pulser and emission lines increased by increasing the operating temperature: the FWHM of the pulser changed from 205 eV at −20 ◦C, to 215 eV at +30 ◦C, and 249 eV at +80 ◦C. It is worth noticing the small broadening of the lines at +80 ◦C, which demonstrates the suitability of our microstrip detector to be used at high temperatures with very good stability of the detector response.

**Figure 13.** (**a**) X-ray spectra from 241Am source after almost 2 and 10 h of acquisition at 30 ◦C in a thermostatic chamber. The very small broadening of pulser and emission lines demonstrates very good stability of the detector response to X-ray exposure; (**b**) linearity error after 10 h of acquisition based on *K* Cu and *L* Np X-ray monoenergetic lines.

**Figure 14.** (**a**) Comparison between three X-ray spectra acquired at −20 ◦C, +30 ◦C, and +80 ◦C in the range 0–60 keV; (**b**) Detail of the X-ray spectra in the range 4–28 keV. Note a small broadening of the pulser line by increasing the operating temperature.
