arXiv subjects

S. Pallada

Publications and source records attributed to S. Pallada.

4 recordsLinked to original sources

arXiv2025

High efficiency quantification of $^{90}$Sr contamination in cow milk after a nuclear accident

Monitoring $^{90}$Sr contamination in milk following a nuclear accident is critical due to its radiotoxicity and calcium-mimicking behaviour, leading to accumulation in bones and teeth. This study presents a high-efficiency protocol for quantifying$^{90}$Sr in cow milk by integrating freeze-drying, high-temperature calcination, ion exchange chromatography and liquid scintillation spectroscopy (LSC). The method was validated using reference milk samples with 0.45~Bq/mL of $^{90}$Sr, achieving a chemical yield of 100 $\pm$ 2\%, ensuring near-complete recovery and accurate quantification. The minimum detectable activity (MDA) was estimated at 0.33 Bq/L under optimal conditions, demonstrating the protocol's sensitivity for low-level detection. A comparative analysis with existing methods centrifugation-based approaches and Dowex resin techniques revealed that our protocol outperforms in both strontium recovery and organic matter elimination. Alternative methods showed lower recovery rates (68 $\pm$ 2\% for Gu\'erin's method, 65 $\pm$6\% for Dowex resin) and suffered from procedural drawbacks, such as incomplete organic matter removal. Applying this methodology to compare samples from certified laboratories confirmed its robustness, with liquid scintillation spectroscopy radioactivity values doubling after 14 days, consistent with secular equilibrium between $^{90}$Sr and $^{90}$Y. While the protocol is optimized for milk, future research should explore its applicability to other food matrices. The high yield, reliability, and ease of implementation position this method as an effective tool for nuclear emergency response and routine radiological monitoring.

physics.chem-ph↗

arXiv2021

High-accuracy liquid-sample $\beta$-NMR setup at ISOLDE

Recently there has been an increased interest to apply the sensitive $\beta$-decay asymmetry detected nuclear magnetic resonance ($\beta$-NMR) technique to biological studies. A liquid-sample $\beta$-NMR setup was build at ISOLDE to allow such investigations and to use the resolution gain of liquid-state NMR in nuclear physics. As part of this setup a magnetic field locking system, a set of printed circuit board shimming coils, a sample exchange system, a set of compact $\beta$-detectors and a custom experimental vacuum chamber were developed. The main magnetic field was stabilized down to the ppm level by the locking system while allowing the direct determination of the absolute magnetic field. The homogeneity of the magnetic field was improved to $\leq$~5~ppm over the sample volume by the shimming coils. Time spent on changing samples was reduced by a factor of five by the liquid sample exchange system. During experiments it was possible to continuously observe the liquid sample thanks to the custom chamber and compact $\beta$-detectors. The absolute field determination allows for a novel way to reference $\beta$-NMR measurements, removing the need for time consuming reference measurements. The improved accuracy and resolution resulting from these innovations allows the study of the distribution of nuclear magnetization and (bio)chemicals using high-accuracy liquid-sample $\beta$-NMR.

physics.ins-det↗

arXiv2020

Magnetic moments of short-lived nuclei with part-per-million accuracy: Towards novel applications of $\beta$-detected NMR in physics, chemistry and biology

We determine for the first time the magnetic dipole moment of a short-lived nucleus with part-per-million (ppm) accuracy. To achieve this two orders of magnitude improvement over previous studies, we implement a number of innovations into our $\beta$-detected Nuclear Magnetic Resonance ($\beta$-NMR) setup at ISOLDE/CERN. Using liquid samples as hosts we obtain narrow, sub-kHz linewidth, resonances, while a simultaneous in-situ $^1$H NMR measurement allows us to calibrate and stabilize the magnetic field to ppm precision, thus eliminating the need for additional $\beta$-NMR reference measurements. Furthermore, we use ab initio calculations of NMR shielding constants to improve the accuracy of the reference magnetic moment, thus removing a large systematic error. We demonstrate the potential of this combined approach with the 1.1 s half-life radioactive nucleus $^{26}$Na, which is relevant for biochemical studies. Our technique can be readily extended to other isotopic chains, providing accurate magnetic moments for many short-lived nuclei. Furthermore, we discuss how our approach can open the path towards a wide range of applications of the ultra-sensitive $\beta$-NMR in physics, chemistry, and biology.

physics.chem-ph↗

arXiv2018

A new beamline for laser spin-polarization at ISOLDE

A beamline dedicated to the production of laser-polarized radioactive beams has been constructed at ISOLDE, CERN. We present here different simulations leading to the design and construction of the setup, as well as technical details of the full setup and examples of the achieved polarizations for several radioisotopes. Beamline simulations show a good transmission through the entire line, in agreement with observations. Simulations of the induced nuclear spin-polarization as a function of atom-laser interaction length are presented for $^{26,28}$Na, [1] and for $^{35}$Ar, which is studied in this work. Adiabatic spin rotation of the spin-polarized ensemble of atoms, and how this influences the observed nuclear ensemble polarization, are also performed for the same nuclei. For $^{35}$Ar, we show that multiple-frequency pumping enhances the ensemble polarization by a factor 1.85, in agreement with predictions from a rate equations model. [1] J. Phys. G: Nucl. Part. Phys./1744084005

physics.ins-det↗