Absolute determination of soluble potassium in tea infusion by gamma-ray spectroscopy

41K(n,γ)42K thermal and resonance integral cross section measurements

“…1524.6(3) 18.08(9) 312.60 (25) 0.336(20) 899.7 (4) 0.052(3) 1920.8 (10) 0.041(4) 1021.2 (9) 0.0201 (14) 2424.3 (7) 0.020(3) 692.0 (8) 0.0033 (7) 1228.0 (15) 0.0024 (11) Although most of these transitions can be seen in the gamma-ray spectra, as will be discussed in Sect. 2.5, only the transition with energy 1524.6 keV was used to measure the 42 K residual activity.…”

“…In the first step, calibrations using 152 Eu, 137 Cs and 60 Co standard reference pointsources considering sum effects were fitted by the least squares method [12,13]. Then, the efficiency ratio between extended-and point-source was determined by simulation, to account for the efficiency changes due both to varying distance and self-absorption, using a procedure developed in [14] and summarized below. We simulated photon energy deposition at the HPGe detector crystal with the MCNPX (Monte Carlo N-Particle eXtended) code [15] using Tally F : 8 (pulse height tally), setting the default electron and detailed photon physics parameters, and using the internal photo-atomic data libraries.…”

“…The detector geometry specification included, besides the detector crystal active volume, an empty internal region and dead layers on the surface of the crystal and contact regions, the HPGe detector capsule, the aluminum absorber and the KNO 3 volumetric source located at 14 cm away from the detector end-cap. Some details of the arrangement, like Ge dead layer thicknesses or the exact position of the crystal in the capsule, were obtained comparing experimental data to simulated values [14] to approximately fit the experimental efficiencies for both gamma-rays from the 60 Co standard reference point-source. In the simulation, the input photon sources were defined by the shape, composition and density of the irradiated samples or standard reference sources.…”

Medidas das seções de choque térmicas e integrais de ressonância das reações 34S(n,)35S e 42K(n,)43K - Aperfeiçoamento por simulação de Monte Carlo

“…São, porém, valores nominais dados pelo fabricante e podem não corresponder aos valores reais de cada detector. As discrepâncias entre os valores nominais e reais são devidas, principalmente ao processo de fabricação [111,112] e envelhecimento do detector [113]. Por esse motivoé necessário ajustar esses parâmetros para que a resposta do detector simulado correspondaà do real.…”

Detetores semicondutores de fótons na investigação das interações dos elétrons e fótons com a matéria

“…• a simulação mostrou-se indispensável na quantificação do K no chá, ao avaliar a auto atenuação dos fótons em uma amostra de grande volume, dispensando a inconveniente construção de uma fonte radioativa específica para o experimento, que precisaria ser descartada após o uso [59];…”