# Characterization of an X-ray Source Generated by a Portable Low-Current X-Pinch
## 3 Results and Discussion
### X-ray Radiography  
The experimental measurements that characterize the X-pinch as an X-ray source, along with X-ray radiography applications, are presented in this section. Several shots were performed using the W X-pinch loads, crossed at 55\({}^{\circ}\) and 98\({}^{\circ}\), based on the previously presented analysis. To increase the optical density, a time-integrated pinhole radiograph recorded for a sequence of eight shots was recorded on film, as presented in Figure 7a. The projected pinhole aperture was created on the film by the sequential shots, which provided the hot spots at various locations. Figure 7b shows a lineout of the film's transmission along the diameter of the cross-point area. Due to the contribution of multiple hot spots and the short-lived energetic electrons [12] in the creation of the overlapped X-ray source, a slightly magnified diameter--larger than the expected 4.2 mm that holds for a point-like source--was observed. It should be noted that emission occurs only from the X-pinch limbs pointing to the anode, denoting the existence of the electron beam that interacts with the cold plasma [12]. The length of the limbs presented in Figure 7a is approximately 1.8 times magnified in relation to their real length. The limbs pointing the cathode do not emit X-rays higher than the cut-off energy of 6 keV; therefore, no signal was recorded, as shown by the radiographs. To evaluate the point projection radiography scheme, a Ti wire sample with a diameter of 50 \(\upmu\)m was used as an image object. Figure 8a shows the time-integrated monochrome-negative radiograph with a typical transmittance (T), lying in the full-scale range (0-1), accompanied by the magnified section of the area of interest. It should be noted that this complementary transmittance (1-T) properly represents the monochrome-positive image of the inverted original radiograph. The numbers N = 0, 1, 2, 4,..., 32 correspond to the multiples of the specified thickness of the thinner first step of the Al step wedge. The film's opaqueness is measured by the so-called optical density (OD). The OD = log\({}_{10}\)(I\({}_{0}\)/I) is a value that measures the film's degree of darkening, and is usually obtained via a densitometer, where I\({}_{0}\) is the incident light intensity measured in the absence of film, and I is the intensity transmitted through the film perpendicular to the film plane. In our case, a scanner with a resolution of 600 dpi (\(\sim\)42 \(\upmu\)m) was used. A maximum OD equal to log\({}_{10}\)(255) = 2.4 can be achieved for an 8-bit grayscale image. Figure 8c shows the OD in relation to N, which is proportional to the log (exposure) [31]. The maximum value of OD observed in Figure 8c is 0.76 (N = 0), and is not included in the step-wedge area. The maximum OD value within the step-wedge area is 0.64 at N = 1, while the minimum is 0.24 at N = 32. The value of 0.18 corresponds to the null exposure (equal to \"film base plus fog\" density). Figure 8d shows the total transmission curves of the step wedge and the Ti wire, including the transmission of the film package. Since OD at the N = 32 step is greater than the null exposure density, we can conclude that the maximum detectable photon energy is above the cutoff energy of \(\sim\)9.0 keV of the transmission profile  
Figure 7: (**a**) Typical time-integrated pinhole radiograph. (**b**) Lineout along the diameter of the cross-point area. corresponding to this step. Moreover, additional experiments on Al-plated W crossed at 55\({}^{\circ}\), using a filter of Pd of 50 \(\upmu\)m in thickness, delivered a minimum optical density for bremsstrahlung emissions in the range of 12-13 keV, including the \"cold\" characteristic L-series lines for W (7.4-11.7 keV), as presented by the magenta curve in Figure 8d. Figure 8a shows that the Ti wire can be identified up to the N = 8 step, while after the N = 16 step (OD = 0.26) the overall OD is of the same order as at the step-wedge OD, in the range of 0.24-0.26.