Prompt gamma-rays induced in Methamphetamine, Fentanyl, Cocaine, and Heroin due to neutrons produced by ²⁵²Cf and a DT nuclear reaction

Prompt gamma rays neutron activation analysis is an analytical technique useful to detect compounds made with low atomic number elements, like narcotics. In this work, Monte Carlo methods were used to estimate the gamma-ray spectra produced when ²⁵²Cf and DT (14.1 MeV) neutrons interact with 12.70 and 20.32 cm-diameter spheres made with methamphetamines, heroin, cocaine and fentanyl. Pulse height spectra show 2.22, 4.44, 5.11, and 6.13 MeV photopeaks induced in ¹H, ¹²C, ¹⁴N, and ¹⁶O. Narcotics are compounds with H, C, N, and O, and the area under the induced gamma rays ¹Hγ (2.22 MeV), ¹²Cγ (4.44 MeV), ¹⁴Nγ (5.11 MeV) and ¹⁶Oγ (6.13 MeV) were calculated. The ¹Hγ/¹²Cγ, ¹Hγ/¹⁴Nγ, ¹²Cγ/¹⁴Nγ, ¹Hγ/¹⁶Oγ and ¹²Cγ/¹⁶Oγ gamma-ray ratios were calculated aiming to distinguish the narcotic. In addition, the linear attenuation coefficients, the effective atomic numbers, and the macroscopic fast neutron removal cross section were calculated. In the interaction between ²⁵²Cf neutrons with the 12.70 cm-diameter narcotic sphere the largest ¹²Cγ/¹⁴Nγ ratio is noticed with cocaine (2.650); the largest ¹Hγ/¹²Cγ ratio is with heroin (16.409), while the largest ¹Hγ/¹⁴Nγ ratio is with fentanyl (33.587). In the interaction between ²⁵²Cf neutrons with the 20.32 cm-diameter narcotic sphere the largest ¹²Cγ/¹⁴Nγ, ¹Hγ/¹²Cγ, and ¹Hγ/¹⁴Nγ ratios are with methamphetamine (2.833, 26.971, and 76.418 respectively). In the interaction between DT neutrons with the 12.70 cm-diameter narcotic sphere the largest ¹Hγ/¹⁴Nγ and ¹²Cγ/¹⁴Nγ ratios are with methamphetamine (8.611 and 20.00 respectively), while the largest ¹Hγ/¹²Cγ ratio is with heroin (0.6450). Also, in the interaction between DT neutrons with the 20.32 cm-diameter narcotic sphere the largest ¹Hγ/¹⁴Nγ and ¹²Cγ/¹⁴Nγ ratios are with methamphetamine (15.922 and 18.700 respectively), while the largest ¹Hγ/¹²Cγ ratio is with heroin (0.991). Induced γ-rays and their ratios can be used to identify the narcotic.