# Improving a PGNAA Technique to Detect Heavy Metals in Solid Samples
## 4 Conclusions  
The signal-to-noise ratio in gamma-ray spectra has been improved using a new optimization for a PGNAA setup consisting of the portable neutron generator Genie 16 and the CeBr\({}_{3}\) detector. The improvement was achieved by rotating the generator 30\({}^{\circ}\) with respect to the detector's axis of symmetry and then adding a 1 cm-thick moderator in the front of the detector. The new setup minimizes the flux of fast neutrons arriving at the detector after passing through the material, which has two major benefits. In the first, we were able to cut the sample size and lower the neutron activation period to nearly half of what we had previously utilized. As a result, we used less heavy metal powder, and Genie 16's life was extended. The other major benefit was improved sensitivity for identifying low concentrations of heavy metals in solid samples, especially when the heavy metals' prompt gamma rays were superimposed on those from the detector. The MDC values for chrome, titanium, and zinc in soil samples were measured to demonstrate this advan  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Element**} & \multirow{2}{*}{\(\mathbf{E}_{\gamma}\) [MeV]} & \multicolumn{3}{c}{**(MDC\(\pm\sigma_{\text{MDC}}\) )**} \\  & & **[wt\%]** & \\ \cline{2-5}  & & **Current Study** & **[PERSON] [22]** & **[PERSON] [23]** \\ \hline Cr & \(1.430\) & \(0.85\pm 0.26\) & \(0.99\) & \(1.20\) \\ \hline Ti & \(0.984\) & \(0.68\pm 0.18\) & \(0.47\) & \(0.54\) \\ \hline Zn & \(1.005\) & \(1.53\pm 0.47\) & \(1.21\) & \(1.70\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: The measured MDC values for Cr, Ti, and Zn in soil samples using 2.5 MeV neutron inelastic scattering prompt gamma rays.  
Figure 8: The yields of zinc prompt gamma ray at 1.01 MeV as a function of its concentration in soil samples. The solid line represents the best fit for the data using the inverse variance weighting scheme.  
tage. The MDC \(\pm\)\(\sigma_{\text{MDC}}\) values obtained for Cr, Ti, and Zn are, respectively, \(0.85\pm 0.26\), \(0.68\pm 0.18\), and \(1.53\pm 0.47\) wt% and are in good agreement with the previously reported values. These data demonstrate the reliability of the PGNAA technique in borehole logging, particularly when drilling and recovering material from the ground to the surface may cause a material disturbance.  
Conceptualization, T.A.-A. and G.A.; methodology, T.A.-A.; validation, T.A.-A. and G.A.; formal analysis, T.A.-A. and F.L.; investigation, T.A.-A. and G.A.; resources, G.A. and A.H.; data curation, T.A.-A., F.L. and A.H.; writing--original draft preparation, T.A.-A.; writing--review and editing, T.A.-A.; supervision, T.A.-A.; project administration, T.A.-A. All authors have read and agreed to the published version of the manuscript.  
This research project was funded by the Deanship of Scientific Research, Princess Nourah bint Abdulrahman University, through the Research Funding Program, Grant No (FRP-1440-18).  
This study did not require ethical approval.  
This study did not involve human.  
The data of this study will be provided upon request.  
The authors declare that there are no conflict of interest.