Total-reflection X-ray fluorescence spectrometry: a simulate study using the Monte Carlo's method

Using the Monte Carlo method was appraised, the capacity of the code MCNP 4B in simulating the phenomenon of TXRF, as well as to evaluate its influences of the detection and incidence angles in the incidence probability of the fluorescent radiation. Just like that two sources were used in different moments, a monochrome beam of 28 keV of energy and a spectrum generated by a tube of W to 30 kV. These sources were used to irradiate samples of 5 nm of thickness supported in a quartz reflector support with 2,5 cm of ray and 3 mm of thickness. In the 63 made simulations the generated picks had energies inside of the foreseen for the picks of fluorescence of the present elements in the different samples. The relationships between the incidence probability of Kβ and Kα picks generated also had values and behavior inside of the foreseen. Varying the detection angle between 0 and 135 degrees significant variations were not detected for the fluorescence incidence probability picks. The radiation totally reflected it decreased with the increase of the angle. With the increase of the incidence angle a relative decrease was detected in the intensity of fluorescent radiation due to the increase of the interaction of the incident radiation. To evaluate the determination of the concentration of elements with MCNP the irradiation of a sample with ten elements you detected it was simulated. All the elements were detected, six of these with smaller percentile mistake than 20% in relation to real concentration. What takes to end that the code MCNP 4B is capable to simulate the phenomenon of TXRF and it has good precision in the determination of the concentration of elements in a sample. (author)