Quenching factor determination with Skipper CCD

• Applicant: Jose Manuel Gomez Guzman, Ph.D.
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544072898

The Quenching Factor (QF) is the ratio between the energy used for ionization and the kinetic energy of a recoiling nucleus. The most successful work to date in determining this quantity in Charge-Coupled Devices (CCDs) was carried out by Chavarría and colleagues. In that study, they irradiated a CCD detector with neutrons and used Monte Carlo simulations to calculate the energy spectrum deposited by them and to quantify the QF values for silicon nucleus recoil energies up to 700 eV. Another work, conducted by Izraelevitch and colleagues using a different technique but also employing neutrons as test particles, managed to observe this quantity up to 1790 eV of recoil energy, in reasonable agreement with the previous values. The determination of the ionization efficiency after the recoil of a silicon nucleus has become a critically important quantity in both neutrino physics and the search for dark matter. The ratio between the energy used for ionization and that deposited as nuclear recoils known as the Quenching factor, plays a crucial role in converting observed ionizations in the sensor into the energy deposited either by the interaction of a neutrino or by potential dark matter particles. This work proposes conducting an experiment based on Skipper CCD technology with the aim of determining the Quenching function below 700 eV. This particular energy range holds significant importance in particle physics. Thus, the outcomes of this study are expected to significantly influence the field since, to date, no experiment has successfully quantified this specific quantity at such low energies. The significance of attaining this range lies in the fact that reactor neutrino interactions, such as Coherent Neutrino-Nucleus Elastic Scattering, along with anticipated interactions with Dark Matter, will transfer nuclear recoil energies to the sensor materials within this interval. The main advantage arising from the proposal presented in this project is the implementation of the innovative Skipper CCD technology. Unlike a conventional CCD, where the readout noise lies between 2 and 5 electrons, these devices are capable of repetitively and non-destructively measuring the charge in each pixel, reducing the readout noise as much as desired. Consequently, these sensors enable the unambiguous identification of the charge in each pixel with negligible uncertainty for all practical purposes. As a result, Skipper-CCDs make possible to explore energy depositions of just a few electrons. Considering that the creation of an electron-hole pair in silicon corresponds to 3.75 eV, this means that Skipper-CCDs enable the exploration of neutron scattering events that deposit energy in the range of a few hundred eV, which due to the Quenching Factor translates to just a few tens of eV of ionization energy. This range was impossible to explore before the emergence of this technology, which has only been in existence for five years.

• DFG Programme: Research Grants
• International Connection: Argentina
• Partner Organisation: Consejo Nacional de Investigaciones Científicas y Técnicas
• Cooperation Partners: Professor Dr. Gustavo Javier Otero y Garzón; Professor Dr. Dario Pablo Rodriguez Ferreira Maltez
• Co-Investigator: Dr. Tobias Chemnitz