Determination of mass attenuation coefficient by numerical absorption calibration with Monte-Carlo simulations at 59.54 keV

International audienceThis study presents a numerical method in order to determine the mass attenuation coefficient of a sample with an unknown chemical composition at low energy. It is compared with two experimental methods : a graphic method and a transmission method. The method proposes to realise a numerical absorption calibration curve to process experimental results. Demineralised water with known mass attenuation coefficient (0.2066 cm 2 .g −1 at 59.54 keV) is chosen to confirm the method. 0.1964 ± 0.0350 cm 2 .g −1 is the average value determined by the numerical method, that is to say less than 5% relative deviation compared to more than 47% for the experimental methods

Well GeHP detector calibration for environmental measurements using reference materials

International audienceA well-type detector installed in the Modane underground Laboratory (LSM) can combine both low background and high detection efficiency and it is well suited for the analysis of small amounts of environmental samples. Reference materials such as IAEA-447 (moss-soil), IAEA-RG-Th1 and IAEA-RG-U1 were used for the detector calibration, owing to a chemical composition close to those of the environmental samples. Nevertheless , the matrix effects and the true coincidence summing effects must be corrected from the full energy peak efficiency (FEPE). The FEPE was performed for a wide range of energy by a semi-empirical method using Monte Carlo simulation (MCNP6), intended for environmental measurements such as lake sediments dating. In the well geometry, the true coincidence summing effects could be very important and correction factors have been computed in three different ways

Same data, different conclusions: Radical dispersion in empirical results when independent analysts operationalize and test the same hypothesis

In this crowdsourced initiative, independent analysts used the same dataset to test two hypotheses regarding the effects of scientists’ gender and professional status on verbosity during group meetings. Not only the analytic approach but also the operationalizations of key variables were left unconstrained and up to individual analysts. For instance, analysts could choose to operationalize status as job title, institutional ranking, citation counts, or some combination. To maximize transparency regarding the process by which analytic choices are made, the analysts used a platform we developed called DataExplained to justify both preferred and rejected analytic paths in real time. Analyses lacking sufficient detail, reproducible code, or with statistical errors were excluded, resulting in 29 analyses in the final sample. Researchers reported radically different analyses and dispersed empirical outcomes, in a number of cases obtaining significant effects in opposite directions for the same research question. A Boba multiverse analysis demonstrates that decisions about how to operationalize variables explain variability in outcomes above and beyond statistical choices (e.g., covariates). Subjective researcher decisions play a critical role in driving the reported empirical results, underscoring the need for open data, systematic robustness checks, and transparency regarding both analytic paths taken and not taken. Implications for organizations and leaders, whose decision making relies in part on scientific findings, consulting reports, and internal analyses by data scientists, are discussed

Evaluation of radionuclide concentrations and external gamma radiation levels in phosphate ores and fertilizers commonly used in Algeria

International audienc

Conception and realization of a parallel-plate free-air ionization chamber for the absolute dosimetry of an ultrasoft X-ray beam

International audienceWe report the design of a millimeter-sized parallel plate free-air ionization chamber 10 (IC) aimed at determining the absolute air kerma rate of an ultra-soft X-ray beam (E = 1.5 keV). The size of the IC was determined so that the measurement volume satisfies the condition of charged-particle equilibrium. The correction factors nec-essary to properly measure the absolute kerma using the IC have been established. Particular attention was given to the determination of the effective mean energy 15 for the 1.5 keV photons using the PENELOPE code. Other correction factors were determined by means of computer simulation (COMSOL and FLUKA). Measure-ments of air kerma rates under specific operating parameters of the lab-bench X-ray source have been performed at various distances from that source and compared to Monte-Carlo calculations. We show that the developed ionization chamber makes it 20 possible to determine accurate photon fluence rates in routine work and will consti-tute substantial time-savings for future radiobiological experiments based on the use of ultra-soft X-rays

Quartz resonator based low-energy ionizing radiation detection.

National audienc

SnO2 thin films used as ammonia sensing layers at room temperature

Gas sensors based on the SnO2 thin films were prepared by dip-coating method starting from their corresponding sols. The as-elaborated thin coatings were afterwards annealed at different temperatures during various times. Their morphology, composition and microstructure were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). The results of electrical and sensing measurements indicated that the sensor annealed at 300°C for 3 hours exhibited the best sensitivity towards the detection of NH3 at room temperature